Manual AOAC Verified Methods Program [PDF]

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AOAC PEER-VERIFIED METHODS PROGRAM MANUAL ON POLICIES AND PROCEDURES



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AOAC PEER-VERIFIED METHODS POLICIES AND PROCEDURES CONTENTS I.



Introduction and General Principles.................................................................................... 3 Purpose Scope Submission of Procedures Distribution/Publication Sunsetting Provision



II.



Outline for Process of Acceptance as a Peer-Verified Method .......................................... 6



III.



Suggested Practice for Characterizing Method Performance ............................................ 8 Minimum Validation Criteria .................................................................................... 8 Suggested Testing for Performance Characterization............................................ 8 Additional or Different Parameters for Qualitative Methods ................................. 10 Generic Descriptions ............................................................................................. 11 Immunoassay and Instrumental Methods ............................................................. 11



IV.



Independent Laboratory Requirement .............................................................................. 13 Identification and Selection of Independent Laboratory ....................................... 13 Method Format ...................................................................................................... 13 Sample Selection .................................................................................................. 13 Precision and Accuracy......................................................................................... 13 Evaluation.............................................................................................................. 14



V.



Technical Review Process ................................................................................................ 15



VI.



Process for Comments on Peer-Verified Methods ........................................................... 17



VII.



Process for Submitting Peer-Verified Methods to AOAC Official Methods Program...................................................................................... 18







CHECKLISTS AND FORMS



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Checklist for Method Development, Characterization, and Ruggedness Testing........................ 19 Safety Checklist for Methods ........................................................................................................ 21 Peer-Verified Methods Format ...................................................................................................... 22 Checklist for Independent Laboratory Protocol............................................................................. 24 Independent Laboratory Report Form........................................................................................... 25 Technical Review Form for Peer-Verified Method Study.............................................................. 26



APPENDIXES Definitions...................................................................................................................................... 27 Estimation and Statement of Uncertainty...................................................................................... 29 Ruggedness Testing Procedure ................................................................................................... 31 Terms of Reference: Peer-Verified Methods Advisory Committee............................................... 34



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AOAC PEER-VERIFIED METHODS. POLICIES AND PROCEDURES I.



INTRODUCTION AND GENERAL PRINCIPLES1



1. Purpose The AOAC Peer-Verified Methods program is intended to provide a class of tested methods which have not been the subject of full collaborative study. Through a less resource intensive process, the program provides a rapid entry point for methods into and recognition by AOAC and a level of validation for methods not otherwise evaluated. Three stages in the validation of analytical methods are (1) establishment of acceptable performance parameters within a laboratory; (2) demonstration of acceptable performance in a second or third laboratory; and (3) demonstration of acceptable performance in an interlaboratory collaborative study. Progression through the stages confers an increasing degree of confidence in the performance of the method and the results produced in different laboratories. Successful testing through stage 2 is the requirement for status as an AOAC PeerVerified Method. By responding to the needs of the analysts and laboratories for an intermediate stage of validation for a wide range of methods, the program provides the tools required to meet some analytical demands. Full collaborative study of Peer-Verified Method is strongly encouraged, especially when further validation will more fully meet user requirements. 2. Scope A candidate AOAC Peer-Verified Method has been subjected to ruggedness testing in the author's laboratory, and performance parameters have been tested in at least one other laboratory. Information on the performance of the method includes evidence of analyte identification, resolution from interferences, sensitivity to concentration, and lower limits of detection or determination. The scope of procedures suitable for testing and submission includes new analytical procedures, revisions of validated methods to extend the applicability or improve the performance, adaptations of methods or procedures to automation, and applications of techniques to new analytical problems.



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There are 4 main phases in the Peer-Verified Methods program: (1) The method author develops a data package characterizing the performance of the method according to method characterization criteria recommended by AOAC. (2) The method author prepares a protocol for testing the performance of the method and recruits a second or additional independent laboratories to conduct the performance test, again according to testing criteria recommended by AOAC. (3) The method characterization data and independent laboratory testing data are submitted to the appropriate Technical Referee, generally chosen from among AOAC General Referees and Methods Committee members, who seeks a review by qualified experts. The Referee, on the basis of a minimum of 2 positive reviews, grants AOAC Peer-Verified Method status to the method. (4) Accepted Peer-Verified Methods are collected and published on a quarterly basis according to a format that includes the data on method characterization, directions on performing the method, and a request for feedback on use of the method by other laboratories. The in-house characterization parameters are compatible with the ruggedness testing that is required as part of the protocol submission for proposed AOAC Official Methods. This facilitates movement of a Peer-Verified Method into the AOAC Official Method study process at some later date. Peer-Verified Methods that are subsequently subjected to full collaborative study will be deleted from the Peer-Verified Method category. Both quantitative and qualitative methods may be studied and submitted for acceptance as Peer-Verified Methods. Rapid "kit" methods may be submitted, but only if there are no proprietary components. Commercial kit methods based on proprietary technology should be submitted to the AOAC Test Kit Performance Tested Program, conducted by the AOAC Research Institute, 481 North Frederick Ave., Suite 500, Gaithersburg, MD 20877-2417, USA; Phone: +1-301-924-7077, Fax: +1-301-924-7089. 3. Submission of Procedures The Peer-Verified Methods process is fully open. Any interested party may submit a procedure for AOAC acceptance, and may submit comments on published procedures. Submissions, queries, and comments should be sent to AOAC INTERNATIONAL, Peer-Verified Methods Program, 481 North Frederick Ave., Suite 500, Gaithersburg, MD 20877-2417, USA; Phone: +1301-924-7077, Fax: +1-301-924-7089. All tested procedures that are submitted are subjected to technical review before acceptance and publication. Oversight for the program is provided by the Peer-Verified Methods Advisory Committee. The Committee also recommends and implements the policies of the AOAC Board of Directors relating to the program. 4. Distribution/Publication



.



Accepted Peer-Verified Methods are published in the Journal of the AOAC INTERNATIONAL (JAOAC). The JAOAC is available on a subscription basis from AOAC INTERNATIONAL, 481 North Frederick Ave., Suite 500, Gaithersburg, MD 20877-2417, USA; Phone: +1-301-924-7077, Fax: +1301-924-7089. When an inventory has accumulated, a method's compendium will become available



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by subscription. PVMs are individually available from AOAC INTERNATIONAL.



5. Sunsetting Provision Accepted Peer-Verified Methods will be reviewed for continued appropriateness after they have been available for 5 years. A notice seeking comments will be carried in The Referee section of the AOAC magazine Inside Laboratory Management. Methods will continue to be available as AOAC Peer-Verified Methods if no negative comments are received. Submitted comments will be appended to the method, resolved by the method submitter or Technical Referee as necessary, or will result in revision of the method, as necessary. Methods which are considered no longer appropriate will be deleted from the collection.



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II.



OUTLINE FOR PROCESS OF ACCEPTANCE AS A PEER-VERIFIED METHOD2



1.



The method author develops the initial method data according to AOAC criteria (see "Checklist for Method Development, Characterization, and Ruggedness Testing").



2.



The method author writes the method in the step-by-step format specified by AOAC that follows the expected flow of laboratory operations (see "Peer-Verified Method Format"). The author is encouraged to incorporate appropriate safety information (see "Safety Checklist for Methods").



3.



The method author develops the design or protocol for second laboratory testing of method performance according to AOAC criteria (see "Checklist for Development of Independent Laboratory Protocol"). He or she is encouraged to discuss the method or seek advice from the appropriate Technical Referee. The AOAC Office can identify an appropriate expert if this is not known to the author.



4.



The method author follows the policy for selecting an independent peer laboratory (see "Guidelines for Selecting an Independent Laboratory") and recruits the laboratory to test the method according to the written protocol. The author prepares any necessary collaborating samples and sends the method, samples, protocol, and form (see "Independent Laboratory Report Form") to the second laboratory.



5.



The independent laboratory conducts the method performance test according to the method and protocol. The two laboratories may communicate to facilitate clarifications and improvements in the method and method directions. The laboratories shall keep a record of these communications.



6.



Within the agreed time, the second laboratory submits its results to the method author, using the report form.



7.



The method author analyzes the data and sends the method development, characterization, and ruggedness testing data and the independent laboratory report to the AOAC Office.



8.



The AOAC Office distributes all material to the appropriate Technical Referee.



9.



The Referee selects at least 2 experts to provide a written technical review, and sends the submitted information (see "Peer-Verified Method Technical Review Form"). Reviewers are asked to return their reviews to the Referee within 3 weeks.



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10.



The Technical Referee acts as follows: 10.1. 10.2. 10.3. 10.4.



11.



If 2 reviews are negative, the Referee notifies the AOAC Office that the method is not acceptable. If 2 reviews are positive, with very minor comments, the Referee notifies the AOAC Office that the method is acceptable with minor revisions. If the initial review is split, the Referee seeks 1 or more additional experts as needed to obtain 2 corroborating reviews. If 2 reviews are positive, but moderate revisions are requested, the Referee requests the revisions from the method author. Once the revisions are satisfactory, the Referee notifies the AOAC Office that the method is acceptable.



The AOAC Office prepares the material for publication in the Peer-Verified Methods Notebook.



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III.



SUGGESTED PRACTICE FOR CHARACTERIZING METHOD PERFORMANCE3



The following performance parameters have been developed primarily for quantitative chemical and physical methods; parameters specifically applicable to qualitative and microbiological methods are presented at the end of this section. The suggested practice is presented in general terms; expected practice should be addressed topic to topic for the specific scientific method proposed. Any questions about what is expected practice in method performance validation for a specific scientific topic should be addressed to the appropriate General Referee and should be documented. 1. Minimum Validation Data The following method validation parameters are normally expected (see Appendix A for definitions): Accuracy Recovery Calibration curve Linearity Limit of detection Limit of quantitation Precision: Repeatability and reproducibility Sensitivity Specificity For any of these parameters that are excluded, a brief explanation should be given to justify why they were not included. 2. Suggested Testing for Performance Characterization Accuracy - Accuracy can be determined by one of these techniques, in preferred order: use of certified reference materials use of reference method of known uncertainty use of recovery from spiked samples Reference material, if available, should be carried through entire procedure with each batch of test samples. If fortified or spiked samples are used, the method of fortification should be described. Recovery - For quantitative methods, recovery of added analyte over an appropriate range of concentrations (mean range variability) may be taken as an indication of trueness.



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The concentration should cover the range of concern including one concentration at target level, one at low end, and one at the high end. Recovery is calculated as follows: % Recovery =



(measured Conc in fort. material - measured Conc in unfort. material) + 100 _______________________________________________________________ (known increment in Conc)



The amount added should be a substantial fraction of, or more than, the amount present in the unfortified material. Guidelines are available for expected recovery ranges in specific areas of analysis. The design of recovery experiments should be appropriate for the intended purpose of the method. Calibration Curve -- A sufficient number of standard solutions is needed to define the response in relation to concentration. The number of standard solutions is a function of the range of concentration. In most cases, a minimum of 5 concentrations of standard solutions (not zero) is appropriate to prepare a calibration curve. The curve should be statistically tested and expressed. Response at various concentrations in pure or defined solvent, and response at various concentrations in matrix(es) should be presented. For nonlinear curves, more standard solutions would be necessary. The curve should be extrapolated above or below the concentrations tested only as necessitated to examine behavior at "zero" and to apply the method of additions. Linearity - Where applicable, linearity can be determined using external analyte standards at 4 nominal concentrations: 0x, x, 1x, and 2x, on 3 separate days (where x is the normal, usually found level or target level for action), or as generally accepted in the commodity testing area.







Limit of Detection - Defined as the mean value of the matrix blank readings (n 20) plus 3 standard deviations of the mean, expressed in analyte concentration. For methods with less than 100% recovery, limit of detection should be corrected for recovery. Limit of Quantitation - The limit of quantitation is the lowest amount of analyte in a sample which can be quantitatively determined with precision and accuracy appropriate to analyte and matrix considered. It can be defined, e.g., as the mean value of the matrix blank reading plus 10 standard deviations of the mean, expressed in analyte concentration. It is not determined by extrapolation. Correction for recovery in the limit of quantitation, if used, should be stated in the method. Limit of Determination/Limit of Decision - The limit is equal to the mean of the measured content of blank samples (n20) plus 6 times standard deviation of mean. Precision - The relative standard deviation of individual results should be determined from different days, different analysts, different calibration curves, different batches of reagents, and AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA  #1#% +06'40#6+10#. 







for different matrixes. Precision is usually defined in terms of reproducibility and repeatability: Reproducibility: Ideally, precision should be measured for performance between laboratories. Obtain values for different samples, different concentrations ( x, 1x, and 1 or 2x), and separate days. Reproducibility data is generated from a minimal number of labs (own lab plus independent lab(s))











Repeatability: This component of reproducibility can be determined within-laboratory. Specific examples in the Appendix suggest practices that are acceptable in various topic areas. Specificity - Reagent blanks and field blanks should be run to ensure no interfering compounds are present. To verify the specificity of the method for the analyte(s) of interest, results should be tested under different experimental conditions, e.g., 2 different analytical principles or 2 different detection techniques. The method should be able to distinguish the analyte from known interfering materials; and the behavior of the analyte during analysis should be indistinguishable from the corresponding standard material in the appropriate matrix. Sensitivity - Sensitivity is normally measured in terms of previously defined parameters. Comparison to Existing Methods - Comparison to an existing method when applicable is strongly recommended (preferably a validated or collaboratively studied method). Depending on topic, a suitable number of comparative analyses, preferably at levels tested in a collaborative study of the "old" method, if possible, are generally sufficient to show equivalent performance. 3. Additional or Different Parameters for Qualitative Methods Recovery - For qualitative methods, recovery may be estimated by comparison of results with an existing method. Linearity - For qualitative methods, the entire response range may be examined by testing a series of test samples and standards consisting of negative test samples, test samples at the specification level, test samples bracketing the specification level, and strong positive test samples. Cross Reactivity- Samples should be tested for cross reactivity with other known entities. Specificity - Usually determined as cross-reactivity. All samples should be tested for crossreactivity with other known entities. Incident of False Positives/False Negatives - For qualitative methods, the precision cannot be expressed as a standard deviation or coefficient of variation, but may be expressed as true and false positive (or negative) rates. These rates should be determined at several concentrations including the specification level. For qualitative methods the incidence of false positives/false negatives may be determined. Data from a confirmatory method comparison should be provided AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA  #1#% +06'40#6+10#. 







if such a method(s) is applicable to the same matrix(es) and concentration range(s). In the absence of method comparison, populations of negative and positive fortified samples should be analyzed. Contact the appropriate General Referee for the calculation of false positive/false negatives for your scientific area. Formulas used in the calculation must be defined and included in the method. Response rates can also be expressed in terms of specificity, sensitivity, and predictive rates. Exact definitions of specificity, sensitivity, and predictive rates as used should be described. Presence/Absence or Qualitative Comparative Tests - For microbiological rapid tests, the following studies can be done by both the rapid test and a culture method Inoculation Test with Viable Cells: 5 different matrix samples 10 different strains of relevant microorganism at 3 different levels (low: 1-10 cells; high: 10-100 cells; blank: no addition) 10 different strains of competitive microorganisms at high level Perform tests in duplicate. Quantitative Microbiological Tests - The same studies recommended for qualitative tests can be done, but the range of applicability should be defined, with comparisons done over that range. Microbiological "Rapid" (Non-culture) Method: A rapid method should be compared with the official culture method, where one exists, over selected strains of microorganism, over selected strains of competitive microorganisms, and over applicable range. When method is intended as a screen, false positive rates may be higher than culture methods, but false negative rate is expected to be 0. 4. Generic Descriptions Performance-Based Descriptions of Reagents and Apparatus - Apparatus and reagents specified in methods shall be specified by performance or generic characteristics rather than brand name. To avoid referring to specific brand products, critical parameters shall be identified and defined. System suitability standards and tests should be established and clearly presented such that the product is defined generically, and equivalency can be readily determined. Vendor or brand names may be included and stated as "examples". A disclaimer should be included as a footnote stating, "AOAC does not endorse the brand names used in this method and are only included in the method as examples." System Suitability Tests - Methods should contain system suitability tests where appropriate for determining acceptability of reagents and apparatus. A system suitability test is a clear, concise, specific technical statement of a definitive test or tests which indicate that all controllable variables attributable to a particular product used in a method are within acceptable limits. This test or tests will be used by the analyst to determine whether a product used in the AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA  #1#% +06'40#6+10#. 







method will have any measurable effect on the method results.



5. Immunoassay and Instrumental Methods Immunoassay: Quality control samples should be used at 0, low, mid, and high analyte range. RSDr of control samples at limit of decision should be