Process: Performance Qualification
The purpose of performance qualification is to provide rigorous testing to demonstrate the effectiveness and reproducibility of the process. In entering the performance qualification phase of validation, it is understood that the process specifications have been established and essentially proven acceptable through laboratory or other trial methods and that the equipment has been judged acceptable on the basis of suitable installation studies.
Each process should be defined and described with sufficient specificity so that employees understand what is required. Parts of the process which may vary so as to affect important product quality should be challenged.(8) In challenging a process to assess its adequacy, it is important that challenge conditions simulate those that will be encountered during actual production, including "worst case" conditions. The challenges should be repeated enough times to assure that the results are meaningful and consistent.
Each specific manufacturing process should be appropriately qualified and validated. There is an inherent danger in relying on what are perceived to be similarities between products, processes, and equipment without appropriate challenge.(9)
c. Product: Performance Qualification
For purposes of this guideline, product performance qualification activities apply only to medical devices. These steps should be viewed as pre-production quality assurance activities.
Before reaching the conclusion that a process has been successfully validated, it is necessary to demonstrate that the specified process has not adversely affected the finished product. Where possible, product performance qualification testing should include performance testing under conditions that simulate actual use. Product performance qualification testing should be conducted using product manufactured from the same type of production equipment, methods and procedures that will be used for routine production. Otherwise, the qualified product may not be representative of production units and cannot be used as evidence that the manufacturing process will produce a product that meets the pre-determined specifications and quality attributes.(10)
After actual production units have successfully passed product performance qualification, a formal technical review should be conducted and should include:
- Comparison of the approved product specifications and the actual qualified product.
- Determination of the validity of test methods used to determine compliance with the approved specifications.
- Determination of the adequacy of the specification change control program.
2. System to Assure Timely Revalidation
There should be a quality assurance system in place which requires revalidation whenever there are changes in packaging, formulation, equipment, or processes which could impact on product effectiveness or product characteristics, and whenever there are changes in product characteristics. Furthermore, when a change is made in raw material supplier, the manufacturer should consider subtle, potentially adverse differences in the raw material characteristics. A determination of adverse differences in raw material indicates a need to revalidate the process.
One way of detecting the kind of changes that should initiate revalidation is the use of tests and methods of analysis which are capable of measuring characteristics which may vary. Such tests and methods usually yield specific results which go beyond the mere pass/fail basis, thereby detecting variations within product and process specifications and allowing determination of whether a process is slipping out of control.
The quality assurance procedures should establish the circumstances under which revalidation is required. These may be based upon equipment, process, and product performance observed during the initial validation challenge studies. It is desirable to designate individuals who have the responsibility to review product, process, equipment and personnel changes to determine if and when evalidation is warranted.
The extent of revalidation will depend upon the nature of the changes and how they impact upon different aspects of production that had previously been validated. It may not be necessary to revalidate a process from scratch merely because a given circumstance has changed. However, it is important to carefully assess the nature of the change to determine potential ripple effects and what needs to be considered as part of revalidation.
It is essential that the validation program is documented and that the documentation is properly maintained. Approval and release of the process for use in routine manufacturing should be based upon a review of all the validation documentation, including data from the equipment qualification, process performance qualification, and product/package testing to ensure compatibility with the process.
For routine production, it is important to adequately record process details (e.g., time, temperature, equipment used) and to record any changes which have occurred. A maintenance log can be useful in performing failure investigations concerning a specific manufacturing lot. Validation data (along with specific test data) may also determine expected variance in product or equipment characteristics.
B. Retrospective Process Validation
In some cases a product may have been on the market without sufficient premarket process validation. In these cases, it may be possible to validate, in some measure, the adequacy of the process by examination of accumulated test data on the product and records of the manufacturing procedures used.
Retrospective validation can also be useful to augment initial premarket prospective validation for new products or changed processes. In such cases, preliminary prospective validation should have been sufficient to warrant product marketing. As additional data is gathered on production lots, such data can be used to build confidence in the adequacy of the process. Conversely, such data may indicate a declining confidence in the process and a commensurate need for corrective changes.
Test data may be useful only if the methods and results are adequately specific. As with prospective validation, it may be insufficient to assess the process solely on the basis of lot by lot conformance to specifications if test results are merely expressed in terms of pass/fail. Specific results, on the other hand, can be statistically analyzed and a determination can be made of what variance in data can be expected. It is important to maintain records which describe the operating characteristics of the process, e.g., time, temperature, humidity, and equipment settings.(11) Whenever test data are used to demonstrate conformance to specifications, it is important that the test methodology be qualified to assure that test results are objective and accurate.
IX. ACCEPTABILITY OF PRODUCT TESTING
In some cases, a drug product or medical device may be manufactured individually or on a one-time basis. The concept of prospective or retrospective validation as it relates to those situations may have limited applicability, and data obtained during the manufacturing and assembly process may be used in conjunction with product testing to demonstrate that the instant run yielded a finished product meeting all of its specifications and quality characteristics. Such evaluation of data and product testing would be expected to be much more extensive than the usual situation where more reliance would be placed on prospective validation.
(1) For example, USP XXI states: "No sampling plan for applying sterility tests to a specified proportion of discrete units selected from a sterilization load is capable of demonstrating with complete assurance that all of the untested units are in fact sterile."
(2) As an example, in one instance a visual inspection failed to detect a defective structural weld which resulted in the failure of an infant warmer. The defect could only have been detected by using destructive testing or expensive test equipment.
(3) For example, in the case of a compressed tablet, physical characteristics would include size, weight, hardness, and freedom from defects, such as capping and splitting. Chemical characteristics would include quantitative formulation/potency; performance characteristics may include bioavailability (reflected by disintegration and dissolution). In the case of blood tubing, physical attributes would include internal and external diameters, length and color. Chemical characteristics would include raw material formulation. Mechanical properties would include hardness and tensile strength; performance characteristics would include biocompatibility and durability.
(4) For example, in order to assure that an oral, ophthalmic, or parenteral solution has an acceptable pH, a specification may be established by which a lot is released only if it has been shown to have a pH within a narrow established range. For a device, a specification for the electrical resistance of a pacemaker lead would be established so that the lead would be acceptable only if the resistance was within a specified range.
(5) Examples of equipment performance characteristics which may be measured include temperature and pressure of injection molding machines, uniformity of speed for mixers, temperature, speed and pressure for packaging machines, and temperature and pressure of sterilization chambers.
(6) The importance of assessing equipment suitability based upon how it will be used to attain desired product attributes is illustrated in the case of deionizers used to produce Purified Water, USP. In one case, a firm used such water to make a topical drug product solution which, in view of its intended use, should have been free from objectionable microorganisms. However, the product was found to be contaminated with a pathogenic microorganism. The apparent cause of the problem was failure to assess the performance of the deionizer from a microbiological standpoint. It is fairly well recognized that the deionizers are prone to build-up of microorganisms -- especially if the flow rates are low and the deionizers are not recharged and sanitized at suitable intervals. Therefore, these factors should have been considered. In this case, however, the firm relied upon the representations of the equipment itself, namely the "recharge" (i.e., conductivity) indicator, to signal the time for regeneration and cleaning. Considering the desired product characteristics, the firm should have determined the need for such procedures based upon pre-use testing, taking into account such factors as the length of time the equipment could produce deionized water of acceptable quality, flow rate, temperature, raw water quality, frequency of use, and surface area of deionizing resins.
(7) For example, the AAMI Guideline for Industrial Ethylene Oxide Sterilization of Medical Devices approved 2 December 1981, states: "The performance qualification should include a minimum of 3 successful, planned qualification runs, in which all of the acceptance criteria are met.....(5.3.1.2.)
(8) For example, in electroplating the metal case of an implantable pacemaker, the significant process steps to define, describe, and challenge include establishment and control of current density and temperature values for assuring adequate composition of electrolyte and for assuring cleanliness of the metal to be plated. In the production of parenteral solutions by aseptic filling, the significant aseptic filling process steps to define and challenge should include the sterilization and depyrogenation of containers/closures, sterilization of solutions, filling equipment and product contact surfaces, and the filling and closing of containers.
(9) For example, in the production of a compressed tablet, a firm may switch from one type of granulation blender to another with the erroneous assumption that both types have similar performance characteristics, and, therefore, granulation mixing times and procedures need not be altered. However, if the blenders are substantially different, use of the new blender with procedures used for the previous blender may result in a granulation with poor content uniformity. This, in turn, may lead to tablets having significantly differing potencies. This situation may be averted if the quality assurance system detects the equipment change' in the first place, challenges the blender performance, precipitates a revalidation of the process, and initiates appropriate changes. In this example, revalidation comprises installation qualification of the new equipment and performance qualification of the process intended for use in the new blender.
(10) For example, a manufacturer of heart valves received complaints that the valve-support structure was fracturing under use. Investigation by the manufacturer revealed that all material and dimensional specifications had been met but the production machining process created microscopic scratches on the valve supporting wireform. These scratches caused metal fatigue and subsequent fracture. Comprehensive fatigue testing of production units under simulated use conditions could have detected the process deficiency.
In another example, a manufacturer recalled insulin syringes because of complaints that the needles were clogged. Investigation revealed that the needles were clogged by silicone oil which was employed as a lubricant during manufacturing. Investigation further revealed that the method used to extract the silicone oil was only partially effective. Although visual inspection of the syringes seemed to support that the cleaning method was effective, actual use proved otherwise.
(11) For example, sterilizer time and temperature data collected on recording equipment found to be accurate and precise could establish that process parameters had been reliably delivered to previously processed loads. A retrospective qualification of the equipment could be performed to demonstrate that the recorded data represented conditions that were uniform throughout the chamber and that product load configurations, personnel practices, initial temperature, and other variables had been adequately controlled during the earlier runs.
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