For new methods implemented after June 15, 2009, there must be an evaluation of the test method analytic validation or verification study (accuracy, precision, etc.) signed by the laboratory director, or designee meeting CAP director qualifications, prior to use in patient testing to confirm the acceptability of the data and approve each nonwaived test for clinical use. LP standard practice is to have the instruments' or analytes' manufacturer provide guidance on method validations, statistical analyses and ensure consistency with industry best practices.
The evaluation must include: 1) a written assessment of each component of the validation or verification study, including the acceptability of the data; 2) a signed approval statement, such as, "I have reviewed the verification (or validation) data for accuracy, precision, reportable range, and reference interval studies (insert other components, as required) for the (insert instrument/test name), and the performance of the method is considered acceptable for patient testing." The Medical Director or designee must also sign a summary statement documenting review of validation studies and approval of each test prior to clinical use. An example statement is, “validations reviewed and performance of method is approved for patient testing.” If data include discordant results, there must be a record of the discordance and investigation of any impact on the approval of the test for clinical use.
For introduction of FDA-cleared or approved test system, the section must do the following before reporting patient test results:
The laboratory must follow manufacturer's instructions or provide validation records if the test has been modified. Following manufacturer's instructions includes performing quality control, calibration, calibration verification, and related functions as applicable to the scope of testing. Reagents, fluids, and disposable materials supplied by the laboratory must meet the specifications in the instructions.
For the purposes of interpreting this requirements, a laboratory-developed test (LDT) is defined as follows: A test used in patient management that has both of the following features.
Each laboratory section must maintain a list of laboratory-developed tests (LDTs) and modified FDA cleared/approved tests implemented by the laboratory. The list must include tests developed in-house, and for laboratories subject to US regulations, tests using analyte-specific reagents (ASRs), and FDA-cleared/approved tests that have been modified by the laboratory.
For introduction of all other test systems (e.g., modified FDA-cleared/approved test, in-house laboratory-developed test (LDT), standardized test book procedures, or when test performance specifications are not provided by manufacturer), the following performance characteristics, as applicable, must be demonstrated before reporting patient test results:
If the laboratory uses fewer samples, the laboratory director must record the criteria used to determine the appropriateness of the sample size. In many cases, a validation study with more samples is desirable.
For modified FDA-cleared/approved tests and LDTs in use prior to July 31, 2016, for which limited validation studies are recorded, ongoing data supporting acceptable test performance may be used to meet the above minimum sample requirement, unless the laboratory must record the criteria used to determine the acceptability of a smaller sample size.
Examples of such ongoing data include records of proficiency testing, alternative performance assessment, and quality control.
Each section must determine the test system's calibration procedures and control procedures based upon the performance specifications verified or established as indicated above.
The section must document all activities for the verification or establishment of performance specifications.
Each clinical section evaluates the appropriateness of reference intervals specific to each analyte. Reference intervals are evaluated: at the introduction of a new analyte / test; if there is a change to analytic methodology; and if the patient population changes.
Laboratory reports that have reference intervals, normal ranges, or interpretations must have the reference values reported with the patient's report to allow proper interpretation of the data.
A reference interval can be verified by testing samples from 20 healthy representative individuals; if no more than two results fall outside the proposed reference interval, that interval can be considered verified for the population studied.
Clinical claims about a test's diagnostic sensitivity and specificity, ability to predict the risk of a disease or condition, clinical usefulness, or cost-effectiveness can be published in the laboratory sections test menu or on the pathology repot. LP sections are not required to make clinical claims about a test, but any claims made by the laboratory must be validated.
A list of current test methods is available to clieants upon request, and also available on the Laboratory of Pathology's website and/or order section requisition forms.
The Section Head of each section determines appropriate method performance specifications. For current test methods, the following performance specifications are available upon request to medical and clinical care staff:
If the laboratory changes its analytic methodology so that test results or their interpretations may be SIGNIFICANTLY different, the change is explained to NIH medical and clinical care staff. This will be accomplished by NIH electronic mail to all clinical clients utilizing the affected sections' service or though Laboratory of Pathology handouts to relevant clinical staff and the Medical Executive Committee.
When a test is put back into production, the following requirements must be met:
This requirement applies to tests that are taken out of production for a time (for example, seasonal testing for influenza). A test is considered to be taken out of production when (1) patient testing is not offered AND (2) PT or alternative assessment, as applicable, is suspended. It does not apply to situations where a proficiency testing challenge is not performed due to a temporary, short-term situation, such as a reagent back order or an instrument breakdown. In those situations, the laboratory must perform alternative assessment for that testing event.
For tests in which proficiency testing (PT) is required, if a PT challenge is not offered during the 30-day period prior to restarting patient testing, the laboratory may perform an alternative assessment of the test. In such a case, the laboratory must participate in the next scheduled PT event.
Clinical sections that use antibodies for clinical analysis must validate new antibodies, including introduction of a new clone, prior to patient testing. The performance characteristics of each assay must be appropriately validated before being placed into clinical use. The initial goal is to establish the optimal antibody titration, detection system, and antigen retrieval protocol. Once optimized, a panel of tissues must be tested to determine the assay's sensitivity and specificity. The scope of the validation is at the discretion of the section's technical supervisor.
Means of validation may include, but are not limited to: 1) correlating the results using the new antibody with the morphology and expected results; 2) comparing the results using the new antibody with the results of prior testing of the same tissues with a validated assay in the same laboratory; 3) comparing the results using the new antibody with the results of testing the same tissue in another laboratory with a validated assay; or 4) comparing the results using the new antibody with previously validated non-IHC tests or testing previously graded tissue challenges from a formal proficiency testing program.
For an initial validation, there should be at least 90% overall concordance between the new test and the comparator test or expected results.
For validation of a nonpredictive assay, the validation should test a minimum of 10 positive and 10 negative tissues. For validation of predictive markers (with the exception of HER2, ER and PgR), the laboratory should test a minimum of 20 positive and 20 negative tissues. In either situation, when the technical supervisor or medical director determines that fewer validation cases are sufficient for a specific marker (e.g. a rare antigen or tissue), the rationale for that decision needs to be recorded. Positive cases in the validation set should span the expected range of clinical results (expression level), especially for those markers that are reported quantitatively.
When possible, validation tissues that have been processed using the same fixative and processing methods as cases that will be tested clinically should be used. If IHC is regularly done on specimens that are not fixed or processed in the same manner as the tissues used for validation (e.g. alcohol fixed cell blocks, cytologic smears, formalin postfixed tissue, or decalcified tissue), the laboratory should test a sufficient number of such tissues to ensure that assays consistently achieve expected results. The laboratory director is responsible for determining the number of positive and negative cases and the number of predictive and nonpredictive markers to test.