James P. Agalloco is the president of Agalloco & Associates, P.O. Box 899, Belle Mead, NJ 08502, tel. 908.874.7558, jagalloco@aol.com. He is also a member of Pharmaceutical Technology’s editorial advisory board.

James P. Agalloco

For at least 20 years, the global parenteral industry has recognized that personnel are the dominant risk relative to microbial contamination in aseptically produced sterile products (1). The contamination source strength of the gowned aseptic processing operator has been estimated in several research studies. Concomitant with this awareness, we have witnessed a series of technological advances that have endeavored to mitigate this contamination risk. These advances can be roughly categorized as follows: 									

separate personnel from the aseptic environment;

limit personnel interaction with sterile materials;

remove personnel from the aseptic environment;

Each of these approaches provides some added measure of security to the process by increasing the degree of separation provided between personnel and the sterilized materials, components, and product contact surfaces required for the aseptic assembly of the sterile product from its individual elements. 

To the extent that these approaches are effective, they can reduce contamination risk in aseptic processing. Designs that most effectively eliminate human-borne contamination have been identified as providing "advanced aseptic processing." The term 

 was perhaps first used at the USP Open Conference on Microbiology in May 2002 (2). During that conference, only two aseptic technologies were discussed under the heading of "advanced": isolators and blow–fill–seal. Over the intervening years, we have witnessed the term 

 come into ever wider use. Considering the goals of aseptic processing, that other technologies intended to meet the high expectations for sterile product manufacturing aseptically should emerge is unremarkable.  

Several technical features distinguish advanced from conventional aseptic processing. We believe the following condition should be met for an aseptic processing technology to be considered advanced: no interventions should be conducted during aseptic operations by gowned employees. In other words, all interventions must be conducted using separative features such as isolator gloves or half-suits. Obviously, this condition also could be met if manned interventions of any type were not required—as can be the case in blow–fill–seal or gloveless isolators. The contamination potential from the human operator, even under the most ideal conditions, is such that the aseptic process may be compromised by even a single manipulation by gowned personnel in proximity to the sterile materials. At a minimum, the allowance of limited human interventions creates risk uncertainty that we believe is incompatible with the concept of advanced aseptic processing.  

A brief historical review of the environmental systems used for aseptic processing is useful to understand the genesis of today's processing technologies (see Figure 1). 

 Figure 1: Aseptic processing family tree.			

Perhaps little known to many current practitioners is the previous use of gloveboxes for aseptic processing before the introduction of cleanroom technology. Clearly, the early practitioners of aseptic processing understood the risk from human-borne contamination and used physical separation between the operator and the so-called sterile field to provide greater control over microorganisms.  

The emergence of the HEPA filter in the mid 1950s changed facility designs and operating practices dramatically. It was now possible to position equipment inside a room and, using gowned personnel, produce larger numbers of units with less human manipulation. This design has continued to evolve to the more advanced barrier designs we see today. Gloveboxes never became obsolete, but labor requirements, throughput limitations, decontamination constraints, and other factors limited their application in aseptic processing. 

The cleanroom dominated the industry as the preferred choice for aseptic processing because it was amenable to high-speed filling, inclusion of processing equipment, and easy adaptation for various applications. Later designs included partial barriers to provide greater separation between operators and sterile materials.  

In the early 1980s, isolation technology was reintroduced to the sterile-products industry as an alternative to cleanrooms. Many practitioners recognized it as an improvement in contamination control relative to even the most sophisticated cleanroom designs then available. Some in the industry were so enthusiastic as to claim that sterility assurance equivalent to terminal sterilization would be possible with this new technology. As with any new technology, its implementation took time, and missteps were made. Although some firms implementing isolation technology experienced difficulties, there were more successes than failures (3).  

Frustrated perhaps by the difficulties they encountered with isolators—particularly relating to decontamination, leak testing, ergonomics, and flexibility of access—several firms endeavored to find a means to obviate the perceived inflexibility of isolators. Thus the restricted access barrier systems (RABS) concept was developed. RABS endeavor to provide the sterility assurance benefits of the isolator with fewer complications. At first, there was no standard definition for RABS and, as a result, there was no standardized minimum performance criterion. Fortunately, this shortcoming has been fully recognized, and a more standardized description of a RABS has been developed recently (4).  

Chronologically, RABS emerged more or less as an offshoot of efforts to implement isolator technology in the mid-1990s. In our view, RABS were conceived not because of contamination-control shortcomings in isolators, but rather in hopes of solving validation and, perhaps most important, to allow more flexible access for repairing and adjusting equipment where necessary.  

Shortcomings and perceived benefits of RABS

From the standpoint of contamination control, no claims have been made that the performance of RABS is superior to that of isolators, but rather that RABS may be easier to implement and more flexible in the manner in which it allows operator access. Of far greater importance is whether RABS represent an improvement relative to patient safety over earlier aseptic technologies.  

Limitations and comparison with isolators.

 Clearly, RABS have the potential to improve contamination control over what might be termed 

 which have been used in cleanrooms for years. It is our opinion, however, that RABS that allow some open interventions by gowned operators fall well short of the ideal of advanced aseptic processing (see sidebar, "Advanced aseptic processing requirements"). 

Advanced aseptic processing requirements			

Moreover, we believe RABS designs are less capable than isolators relative to their ability to exclude microorganisms for several reasons. First, isolators provide a measurable pressure differential between the enclosed environment and the operator. In contrast, RABS rely on air overspill to exclude contamination from the surrounding environment in which the aseptically gowned operator is located. 

Second, isolators are subjected to a reproducible decontamination process (in some cases, this is a sterilization process) performed by a microprocessor-controlled system delivering a sporicidal agent in a consistent manner each time. The effectiveness of that process can be supported by the multiple-log kill of resistant microorganisms. Although it is true that RABS and the rooms surrounding them also can be reproducibly decontaminated by microprocessor-controlled equipment, this advantage is immediately lost if gowned operators are given free access to the critical zone at any time during production. Of course, should manual disinfection be required after such gowned interventions, comparable levels of control would be impossible to demonstrate. This treatment might be as effective as what is performed on the isolator from a chemical lethality perspective, but reliance on humans for execution makes it susceptible to occasional error or omission. Moreover, because this activity requires the operator to access the interior of RABS, there is always the contamination potential associated with any aseptic intervention. 

Third, the product contact surfaces such as feeder bowls and stoppering equipment inside the isolator can be preinstalled and treated with a sporicidal agent with the isolator in the same process used to decontaminate the isolator. RABS designs allow these items to be sterilized remotely, transferred to the RABS, aseptically installed, and readied for operation. This represents a clear risk of microbial contamination that cannot be easily avoided. 

Fourth, by the very nature of the RABS design, there may be areas of the installation that personnel cannot reach easily that require treatment. Consider for example a RABS installation with a large lyophilizer. The ability of the gowned operator to disinfect the interior of RABS adequately without physically entering the system is remote. This presents a potential microbial insult to RABS of such magnitude that a claim for this practice or design as being an advanced aseptic process cannot be easily supported. 

Fifth, aseptic processing isolators operating under positive internal pressure are the preferred means for the filling of sterile cytotoxic products. RABS designs cannot be used for this type of product because the level of containment is minimal. 

Finally, the suggestion that the doors to RABS can be opened for a major intervention, and then filling resumed after a "high-level disinfection" process seems tenuous at best. As noted previously, "high-level disinfection" by gowned personnel may not be truly reproducible nor without risk. Any intervention that requires the doors of the RABS to be opened is unacceptable within the context of advanced aseptic processing. We would have the same objection were this to occur in an isolator, but under those circumstances, no one would consider the system acceptable for continued use without a full decontamination comparable with the initial treatment. 

 Some perceived advantages of RABS designs have been identified as follows: 					

flexibility of access—but not without potential open intervention risk;

lower cost—lower initial capital investment is probable, but because full aseptic core zoning and gowning are required, operating costs are likely higher;

shorter validation timeframe—this may be true, but there is not enough of a track record to know for certain;

more conventional in terms of validation requirements—no performance standards for RABS have been defined, however, and when they are defined, it is uncertain whether they will be based upon manned cleanrooms or isolation technology.

It is our strong belief that although RABS may be superior to manned cleanrooms, they cannot attain the certainty of performance demonstrated by present-day isolators. Perhaps the most appropriate application for RABS would be as retrofits to existing aseptic processing facilities. In this situation, the existing infrastructure of cleanrooms, corridors, and gowning rooms would remain largely unchanged, with RABS concepts applied solely to the filling lines. We remain highly skeptical relative to the utility of RABS in installations with large or multiple lyophilizers, given the access limitations they impose. These installations, however, while representing a potentially valuable contamination-control improvement over conventional cleanrooms, fall well short of advanced aseptic processing. 

Ideal RABS for advanced aseptic processing			

Improving RABS for advanced aseptic processing

We can define a RABS design that meets industry expectations for advanced aseptic processing (5). To realize that designation we believe the RABS design must possess specific attributes (see sidebar, "Ideal RABS for advanced aseptic processing"). To our knowledge, this type of design has not yet been used, but some operations have come very close to this ideal, and newer technologies may make it feasible. With this type of design, we would also impose the following additional requirements: 					

Internal decontamination requirements would be comparable to isolators.

Media fill and environmental monitoring requirements in the critical zone are comparable with those for isolators. Monitoring in the surrounding environment also is required.

Glove-leak testing (where gloves are required) would be required.

Personnel accessing the environment require full aseptic gown certification.

If lyophilization is required, then automated loading and unloading must be provided with freedom from personnel access.

Environmental monitoring should be performed in the same manner as isolators.

The use of RABS for extended campaigns must be explored, and the operational conditions that must be met must be determined.

Future considerations for RABS implementation

If RABS are to become a useful technology in our industry, what will be required and what can we expect to occur? First, the fundamental characteristics of RABS for advanced aseptic operations as we have endeavored to define must be broadly accepted. Also, it is quite likely that the validation of RABS designs will be fairly similar to isolator validation. 

As in all forms of aseptic processing, the elimination of interventions must be paramount. Advanced aseptic processing cannot exist when personnel have the ability to intervene at will. In addition, RABS designs probably offer the most direct and cost-effective route to upgrading existing aseptic facilities. Finally, elements of RABS may be an appropriate solution to some of the most common interventions in manned aseptic processing (

We doubt that any aseptic processing system, including RABS, which is tolerant of open-gowned aseptic interventions, will have a long shelf life based upon current and developing technology. We believe aseptic processing technology will continue to evolve toward the complete elimination of operator interventions of all kinds. In fact, gloveless isolators already exist and have been in use in some aseptic processing industries for about 10 years.  

Therefore, technologies that are designed to allow easy intervention will lack staying power as machine automation and robotics replace operators. In our view, RABS' principal utility will be in the reduction of risk in existing facilities, but it will not be the technology of choice for new facilities. Of course, it is equally possible that separative enclosures such as isolators will suffer the fate of obsolescence as well. The authors have no technology preference regarding the elimination of human interventions and hence human contamination risk. Given the rapid advancement currently underway in flexible robotics, equipment self-diagnostics and self-correction, information technology, in-process control, and so forth, it is quite possible that human intervention can be eliminated by means other than barriers or separative enclosures such as isolators in the near future. In fact, systems that came very close to this ideal have been in operation since the late 1980s.  

Validation of advanced aseptic processing is perceived to be substantially more difficult than conventional aseptic processing. Witness the claimed difficulties with isolation technology at some firms. A significant number of advanced aseptic processes, however, have been successfully validated. Risk- and science-based regulation should favor the systems that are best are reducing risk. Recently, FDA has sought to ease the validation requirements for advanced aseptic systems by reducing validation expectations where justified by risk management. We believe this is a great step forward. It seems logical to us that the greatest validation benefits should come to processes that truly eliminate human interventions and to those with the most capability for in-process control. We look forward to further definition from FDA so that industry has a clear understanding of what is possible in terms of reduced validation activity as a function of risk mitigation.  

We believe that a definition for advanced aseptic processing much like that proposed at the USP Open Conference in 2002 is most appropriate. Thus, advanced aseptic processes are those that eliminate direct intervention by personnel. For RABS to be an appropriate technological solution, it must be very isolator-like. Systems that tolerate any form of direct intervention by gowned personnel are nothing more than highly evolved conventional cleanrooms with gowned personnel.  

Articles

Any aseptic processing technology that allows intervention by gowned personnel during operation cannot be considered an advanced technology. Although a standardized definition of restricted access barrier systems has been developed, these systems fall well short of being classfied as advanced technologies. 

RABS and Advanced Aseptic Processing

Aseptic processing is perhaps the most critical of all production activities performed within the healthcare industry (1, 2). The risks to patients are higher for aseptic processing than any other process in current use, and the technologies used for the aseptic production of sterile products are among the most complex and costly in the industry. Regulators worldwide recognize the importance of proper practices for aseptic processing and have established several guidance documents pertaining to its application (1, 3). 

Firms that produce aseptic products, pharmaceuticals, or medical devices have attempted to reduce the microbial contamination risk associated with their assembly by using individually sterilized materials and packaging in pristine environments. Beginning in the 1950s, firms relied for years almost completely on cleanroom technology in which critical activities were performed by gowned personnel.  

As product sophistication and machine automation capabilities advanced, industry increased its use of machinery to produce many aseptically processed sterile products. Despite these advances, human presence in aseptic areas, though substantially reduced, has remained a constant. Although the aseptic fill rooms of the 1960s and 1970s may have used several operators per line, that number has often been reduced to one in newer installations using the most advanced equipment. This reduction was made with the knowledge that personnel have always been the single greatest source of microbial contamination in the aseptic process, and reducing their influence on the aseptic process presence should be a high priority.  

One must only visit facilities using automation, blow–fill–seal or form–fill–seal, robotics, remote particle sensors, and other technologies to understand that patients who are administered aseptic products would be at greater risk had these advances not taken place during the past 20–30 years. 

This article reviews the history of isolator implementation and address why the vast majority of these obstacles are either no longer meaningful, nonexistent, or were self imposed without good reason.  

The current pinnacle of aseptic processing capability is isolation technology, in which personnel have been removed from the aseptic environment almost entirely. In the most advanced isolator installations, operators perform only a limited number of tasks, roughly equal in number to those required with an advanced filling system in a cleanroom. The isolator makes those tasks substantially safer because the gloves are hermetically sealed to the isolator wall. This barrier provides a degree of separation between the operator and the critical operating environment that is substantially more secure than is possible in a manned cleanroom containing aseptically gowned personnel.  

Designs are on the drawing board to take this concept substantially further, using robotics and advanced equipment designs inside an isolator, thus eliminating the need for gloves. The introduction of these systems is some years away. In the interim, isolators are considered the best available technology for the production of aseptic products. This rationale was acknowledged by the US Food and Drug Administration in its 2004 aseptic processing guidance, and similar perspectives were advanced by leaders in the European and Japanese regulatory communities (in which the introduction of isolators for aseptic processing has progressed at a far greater rate than within the United States) (1, 3, 4). 

It was first predicted nearly 15 years ago that isolators would make the conventional manned cleanroom obsolete (5, 6). At that same time, I identified 10 obstacles to isolator implementation that had to be overcome. These obstacles included:   					

attempts at replacing terminal sterilization resulted in over-specification and validation problems;

perceived materials transfer or ergonomic problems;

reports of excruciatingly long timelines;

chemical activity of decontaminating gasses and residuals;

existing facilities and equipment designed for conventional operation;

expected advocate-created confusion and FDA skepticism;

The transition to isolation technology from manned aseptic processing was slower than anticipated. Consequently, nearly five years after my initial prediction, I added some additional items to my list of delaying influences (7). Between 1997 and 1998 these items were added: 					

over emphasis on the importance of leaks; 

management of mouse holes considered problematic;

requiring Class 100 laminar flow internally;

requiring Class 10,000 or better outside;

higher initial cost of isolator installations.

It is now 2006, and although many technological advances (

 cell phones, satellite radio, DVDs, global positioning systems) have become commonplace throughout our global society, the pharmaceutical industry has been unconscionably slow in implementing a superior technology in one of its most critical areas. Industry should be cautious with new technologies but it should not essentially ignore them or worse yet, actively oppose them, as has been the case in far too many companies. We owe our patients sterile products with the least possible potential for contamination, within the limits of the available technology, especially when the technology also may be the most cost-effective one available. 

Some of the aforementioned issues can be dismissed rather easily. The suggestion that an exclusionary practice such as aseptic processing could prove equivalent sterility assurance and reliability to a destructive process is patently absurd. Newer advanced aseptic processing technologies such as robotics in isolators and closed-vial filling can come very close to the same levels of sterility assurance that are achieved by terminal sterilization, however they are still exclusionary and thus must be still considered to present more of a risk to the patient. This could never be possible and it led to extraordinary measures to demonstrate that an isolator could operate at an unrealistic level of perfection.*  This belief led to interminable, self-created delays as firms endeavored to satisfy them. The user requirements specification (URS) derived from this inappropriate expectation led directly to several of the obstacles. 

Every closed system has leaks, no matter how sophisticated. Manned aseptic cleanrooms rely on continuous air over-spill to purge the facility of contamination. Moreover, leaks are perhaps of greatest relevance during isolator decontamination, and even then, they are a safety issue not a true aseptic concern. A defined leak rate established by safety requirements during decontamination is now considered acceptable (8). 

 The largest openings in most filling isolators are where  containers enter and exit. Relatively simple pressure management allows these ports to be managed with ease. 

 Attempts to validate the absolute sterility of an isolator interior that merely provides an operating environment led to lengthy (and unnecessarily harsh) decontamination cycles with no meaningful benefit. The cycles had the concomitant result of weakening gloves and other soft parts, increasing corrosion possibility, and delaying aeration of the enclosure. Inoculating every possible material in the isolator to establish the absence of a substrate effect is perhaps the worst example of URS excess. The isolator is intended to provide an environment for aseptic processing, not administering injections to patients. Isolator decontamination now is recognized as a practical solution before aseptic processing. Sterilization of product contact surfaces during the overall decontamination (or separately) is accomplished easily. With the reduction in process expectation has come a reduction in adverse effects on the exposed materials (9). 

 Isolator decontamination difficulties are readily overcome by proper humidification of the system. Reports of failure and difficulties are largely associated with humidity conditions outside the effective range. It should be noted that spores are rapidly inactivated by liquid H

, and thus concerns about the adverse effects of too much humidity (

 condensation) are misguided. An unfortunate outgrowth of decontamination problems is the expectation that conditions in the gas phase may be measured and the results of the measurements can be used to confirm process efficacy. Success with these vapor analysis systems is inherently limited, because they cannot measure conditions on the surface in which lethality may be derived from condensed H

Gloves in isolators may be necessary for aseptic setup and interventions. The use of isolation technologies does not eliminate the need for aseptic techniques at all times. Direct contact of the gloves with sterile materials is inappropriate; tools must be used at all times. The effect of minor glove penetrations has been the subject of several recent studies. The consensus is that concerns relative to their integrity and their effect on asepsis are overstated. With proper equipment design and quality components, interventions of all types can be substantially reduced, which is a desirable objective in every aseptic operation. Isolators without gloves are now possible and will make any concern for glove integrity moot (8). 

*Providing a level of confidence in aseptic processing using isolation technology equivalent to a terminal sterilization treatment of a sealed container will never be possible in the absolute sense. Nonetheless, with the elimination of interventions within an isolator through the use of automation and robotics, the differences in performance may be indistinguishable. What must be acknowledged is that the isolator doesn't need to be perfect to realize a comparable capability. The key requirement is that it be able to operate with minimal (and preferably no) human activity internally.

In general, industry agrees that the classification of the surrounding environment has little effect on the ability to provide suitable conditions for aseptic processing within an isolator, whether open or closed. ISO 8 conditions have usually been adopted as the acceptable practice and, with restricted access, make an ideal environment for isolator placement. 

 Equipment manufacturers have overcome many of the perceived component handling and material-transfer concerns. Some of these are overly complex, resulting in additional problems. But simpler designs have eliminated this concern. 

 Marketplace demands have eliminated some of the less-capable isolator manufacturers, and the remaining suppliers have increased the sophistication of their designs and control systems. Materials for construction have been upgraded as well, and through licensing agreements, rapid transfer ports will sometimes be available for interoperable configuration. 

 Isolator designs may be substantially simplified if the need for unidirectional airflow is eliminated. Currently, this process is necessary to purge the aseptic processing environment of viable and nonviable particles typically associated with gowned personnel, but by removing personnel from within the isolator environment, unidirectional airflow is no longer beneficial or necessary. In isolator systems in which unidirectional airflow is not present, no adverse effect occurs (9). 

Globally, regulators have shifted their perspective from one of initial caution (an appropriate consequence of their relative novelty and the excessive claims of some early practitioners) to acknowledgment that isolators offer a more secure environment for aseptic processing than other available technologies (1, 3). 

From an overall technical perspective, it should be evident that success with isolation technology is an attainable reality. The perceived difficulties with its implementation have largely been overcome. At present, there exist only two remaining objections to its broader use: time and money. A rather important duo, but even these concerns aren't all that valid.  

The time required for the implementation of any project is a direct result of the difficulties associated with its implementation. Isolators were badly served early on by some of their more vocal proponents. Expectations and public statements that isolators were going to replace terminal sterilization led to unattainable goals, frustrated users, extended timelines, and bad feelings at some firms. Isolator owners established more realistic goals or met them without substantial difficulty. Industry surveys have indicated that at least two major firms operate more than 20 aseptic processing isolators each (4). I participated in a smaller project in which the purchase decision for a custom system was made in mid-May and the firm performed successful media fills in December (12). Design, fabrication, qualification, decontamination-cycle development, and validation were completed without any delay or difficulty. Numerous other projects of larger scope have experienced similar success. 

Increased initial costs for systems using isolation technology have been a cause for some concern. Cost may vary but is typically in the range of 30–70% above that of a manned cleanroom. The substantially lower costs of operation for isolator systems are undisputed. Savings accrue in utility consumption, gowning materials, labor use, decontamination, and environmental monitoring. Hard numbers on comparative costs of operation are difficult to generate. Nonetheless, the numbers of isolators installed, especially by those firms with numerous installations, suggests that the real economics are more favorable than the projections would suggest. 

The aseptic processing isolator has truly arrived. The earlier concerns associated with the implementation of this technology have essentially disappeared, and there is every reason to believe that early predictions regarding the replacement of cleanrooms by isolators will be proven correct. Ensuring success with isolation technology requires a realistic user requirements specification and an environment open to novelty. Those reasons alone are sufficient to realize the advantages of this technology without the tribulations of people that asked for the impossible and then complained mightily when they could not realize it. Realizing the substantial improvement in patient safety requires the recognition that there exist few, if any, valid reasons not to install an isolator for a new aseptic processing facility. 

  is the president of Agalloco & Associates, PO Box 899, Belle Mead, NJ 08502, tel. 908.874.7558, 

Guidance for Industry. Sterile Drug Products Produced by Aseptic Processing—Current Good Manufacturing Processes

 2. J. Agalloco and J. Akers, "Risk Analysis for Aseptic Processing: The Akers–Agalloco Method," 

 3. PIC/S, "Recommendation–Isolators for Aseptic Processing and Sterility Testing" (Pharmaceutical Inspection Convention and Pharmaceutical Co-operation Scheme, Geneva, Switzerland, 2004). 

 4. J. Lysford and M. Porter, "Barrier Isolators History and Trends,"

There are few, if any, valid reasons not to install an isolator in a new aseptic processing facility. 

Thinking Inside the Box: The Application of Isolation Technology for Aseptic Processing

Many in the pharmaceutical industry consider aseptic processing to be among the more difficult activities to execute properly. A substantial number of variables affects the safety of sterile products manufactured aseptically. The design and operation of an aseptic production facility must minimize the risk to the patient. This article presents a new approach to risk assessment for aseptic processing that emphasizes the contributions of personnel. 

In September 2004, the US Food and Drug Administration issued the long awaited guidance on sterile drug products produced by aseptic processing (1). That month, FDA also published 

Pharmaceutical CGMPs for the Twenty-First Century—A Risk-Based Approach

. (2) Each of these documents refers to the other, but there is no substantive information offered in either to assist the practitioner in establishing a risk-based approach for the design and control of aseptic processing operations. 

Numerous pre-existing risk-analysis methods have been adapted for the pharmaceutical industry, including:  					

Hazard Analysis and Critical Control Point (HACCP);

Failure Mode, Effect, and Criticality Analysis (FMECA).

These commonly used methods have proven successful in a variety of applications. None, however, was ever specifically intended for application to aseptic processing, which relies on a large number of variables and has the lowest tolerance for failure of any process in the entire industry. Simply put, failure in aseptic processing is unacceptable, and a suitable risk-analysis method must incorporate all of the factors affecting product sterility and patient safety. The risk-analysis approach used must incorporate the recognition that there is no acceptable level of risk associated with sterile products, regardless of the manufacturing method. The goal is, and must always be, perfection in all elements of sterile product manufacturing, especially when products are made using an aseptic process (3). With this in mind, the authors embarked on an evaluation of previously established risk-evaluation methods as applied to aseptic processing. 

The risk-analysis method that is chosen must focus clearly on the manufacturing activities that are essential for success in aseptic processing. This normally is manifested by a concern for criticality. Not all of the constituent activities of a process being evaluated have an equal effect on the end result. 

 as defined within FMECA, is a multiplication of the criticality of an occurrence by its frequency. This definition seemingly can be applied directly to aseptic processing. Determining what constitutes an "occurrence," however, is generally difficult in aseptic processing. One could argue (perhaps incorrectly) that environmental monitoring results can provide a measurement of occurrences, but this assumption is theoretical at best. Environmental monitoring, especially in the ISO 5 environments commonly used for aseptic processing activities, hardly can be considered a quantitative or fully effective tool. In the typical ISO 5 environment, microbial contamination is detected only rarely, and even the most aggressive sampling plans only sample a limited amount of air or surfaces* (see endnotes). Another drawback of viable environmental monitoring is that results are unavailable in real time when using common growth and recovery methods. Nonviable particle monitoring, which is available in near-real time, has never been correlated sufficiently to viable data. The authors consider it of limited value in aseptic risk assessment. 

The authors believe that there is a straightforward way to analyze risk in aseptic processing. 

is by general agreement a function of the release of human-derived contamination into the operating environment. The full extent of human contamination risk is substantial: a gowned operator may release as many as 10,000 colony-forming units (cfu) or more per hour (4, 5). The estimated value is derived from operators performing controlled and defined movements immediately after donning sterile gowns. These methods merely provide a way to estimate the intensity of the contamination source from activities substantially different from those performed during aseptic processing. Direct application of these data to aseptic processing unfortunately is not possible, given the differing environments and activities. 

Whyte developed a risk-assessment model based on his research on microbial deposition, which was an extension of his earlier efforts with settle plates (5–8). The premise behind this approach is the recognition that personnel are the primary source of contamination. It assumes the mechanism for dispersion of that contamination is airborne deposition. Whyte's model is the following: 

Number of microbes deposited on product = 

 is the concentration of microbes in the source (people), 

 is the quantity of air or material dispersed from a source over time (usually cfu/m

 is the proportion of organisms effectively transferred, 

 is the proportion of organisms that arrive into the product area, and 

 is the time during which microbes could be transferred. 

Whyte also has proposed a slightly simpler deposition model for risk evaluation in which the risk from microbial contamination is defined as: 

 is the microbial contamination on or arising from a source (

 is the proximity of the source to the critical area (one can assume the contamination decreases as the inverse of the square of the distance), and 

 is the effectiveness of the control method (

 isolator, restricted-access barrier systems [RABS], automation, sealed container, intervention frequency). 

Whyte chose five levels of risk for each of the terms in the equation: 0 indicates no risk, 0.5 indicates very low risk, 1 indicates low risk, 1.5 indicates medium risk, and 2 indicates high risk. In the case of factor 

 (effectiveness of control), he suggests 0 for "full barrier control." This means that, should a truly full barrier exist, the overall risk effectively would be zero. Products such as sealed vials that mimic the capabilities of a closed isolator system logically would fall into the "full barrier control" category (9, 10).  

The authors' main criticism of this risk model is that it may underestimate process risk because it implies that an exclusionary process such as aseptic processing could produce a level of contamination control effectively equivalent to terminal sterilization. Certainly aseptic processing, in its present state, cannot be considered equivalent to terminal sterilization. Although it may be possible in the future for extremely advanced aseptic processing to achieve levels of actual product safety equivalent to those attained using terminal sterilization processes, there are no aseptic systems currently in operation that can attain process capability comparable with that of a terminal sterilization process. Furthermore, the destructive control afforded by terminal processes enables scientists and engineers to assess risk far more reliably than is possible in aseptic processing. 

The deposition models for contamination risk analysis have their advantages and disadvantages. They take into account the following technical conditions that have been included in informal risk assessment for years: 					

the estimated microbial content of the surrounding air.

The authors believe that a major disadvantage of these models is their inherent assumption that the deposition of microorganisms from the air represents the only vector for contamination. Having observed numerous aseptic processes over the years, the authors find that approach inadequate. In many aseptic processes, operators must approach sterile materials with tools and protective measures. Focusing on personnel seems more appropriate. Although deposition may be the mechanism of dispersion, one must not be so focused on the containers that one ignores the potential presence of microorganisms in other stages of the aseptic process. The authors have developed an approach that is much broader and is not limited to the effect on the container alone. 

In addition, the authors believe that assumptions regarding the microbial content of air are potentially misleading. It is tempting to consider that the worst-case content of airborne microbial contamination is that given in the common international recommendations (

The authors take a broader view of the contamination potential in aseptic processing and recognize that contamination comes from various sources. Table I presents a vision of risk assessment that has been used for many years (11). This vision draws upon that broader view and incorporates concerns that affect each of these tasks and the others that affect sterility assurance for aseptically produced sterile materials.  

 Table I: Validation of aseptic processing.			

There are several basic concepts that result from this conception of aseptic processing. The effect of personnel on the aseptic process is all-important, and one must define risk to sterility predominantly in terms of the human activities required to execute the process. Other factors can be included, but focus on the contribution from personnel must be paramount. Risk is directly related to the number of human interventions required during the process: the fewer interventions required, the lower the risk of contamination. Interventions can be scaled relative to criticality. The type of interventional activity performed and the proximity of that activity to sterile materials suggest that some form of weighting of the intervention's influence is appropriate. 

Other factors in contamination exposure include: 					

the container-opening diameter (smaller diameters are preferred, following the deposition models described previously);

the length of time the container is exposed to the environment, from its initial entry until its closure;

the length of time the closure is exposed to the environment before the container is sealed;

lyophilization, which can increase the exposure risk as a result of extended exposure time of the unsealed container and a need for additional interventions;

automation that significantly reduces the need for operator interaction with sterile equipment and materials;

complex assembly activities, which depend to a large extent on operator skill and thus increase risk;

novelty of personnel, equipment, or procedures, which increases risk.

One of the authors' fundamental premises is that 

all ISO 5 environments are not equivalent in their ability to support successful aseptic processing. 

Limitations to microbial detection in these clean environments make distinctions among them subjective. Nevertheless, the authors acknowledge that some technologies are superior to others in their ability to limit microbial intrusion and contamination. The environmental conditions in which the aseptic process is performed were included as a major factor in risk assessment. Environmental conditions are an overall factor in the present model. The application of these general principles and others of similar intent form the basis for the authors' risk-assessment model. 

The pharmaceutical industry seems to give little consideration to risk mitigation during equipment selection. Only slightly more consideration of risk mitigation is given during the choice of container or delivery system. Ease of assembly and operation can make a substantial difference in risk exposure. Reducing the number of required aseptic connections is beneficial. Automated component handling is helpful in reducing risk. Low in-process adjustment and maintenance requirements should be key specifications. Equipment that can operate with minimum accumulation time also is desirable because it reduces exposure. 

Akers–Agalloco method for risk assessment

The objective of this effort is a method that is: 					

based on real-world risk factors rather than more theoretical concepts;

based on an occurrence and criticality model;

prone to reward processes in which interventions are reduced to a minimum.

Occurrence in the present model includes the quantity and criticality of interventions as well as other elements of process risk that are indirectly related to the core activity of aseptic filling. It includes: 					

background environmental risk, which is distinct from the filling environment;

aseptic compounding risk, which is heavily dependent on interventions;

aseptic setup risk, which is heavily dependent on interventions;

aseptic-filling risk, which is heavily dependent upon interventions and calculated separately for manual and machine processes;

The authors present a new approach to risk assessment for aseptic processing that emphasizes the contributions of personnel.

The Akers–Agalloco Method

The complete elimination of human-derived contamination is possible only with the elimination of human intervention.

Aseptic Processing: A Vision of the Future

The sterility testing of samples from an aseptic process may be considered an entirely separate aseptic process that is subject to the same types of adventitious contamination as the aseptic process itself.

Importance of Background Microbial Levels in the Manufacture and Testing of Sterile Products

This article outlines a comprehensive approach for organizing a firm's aseptic operations, including planning for routine and nonroutine interventions, establishing effective process simulations, and determining which vials to incubate.