How to verify IVD reference intervals?
1. Verification conditions
When using a verification method to determine the reference interval of the declared reagent, the following conditions need to be met:
First, the research on original reference intervals should be systematic, comprehensive and credible, such as published and implemented clinical testing reference interval standards;
Second, the detection system needs to be comparable;
Third, the pre-analytic factors of the reference interval study need to be comparable, such as the status of the reference individual, specimen collection and processing procedures, etc.; fourth, the suitability of the reference population. The reference population used in the original reference interval study should be consistent with the intended applicable population of the applied reagent in terms of geographical location, demographic characteristics, etc., or include the above reference population that meets the requirements for the number of reference samples for establishing the reference interval. If the above conditions cannot be met at the same time, the applicant needs to establish its own reference interval according to the method described above.
Applicants should use methodological comparison methods to study the comparability of the detection system between the declared product and the original reference interval when it was established. For methodological comparison research methods, please refer to the "Technical Guiding Principles for the Clinical Evaluation of In Vitro Diagnostic Reagents Exempted from Clinical Trials" (National Medical Products Administration Announcement No. 74, 2021). Note that the detection results of the two detection systems should be highly consistent. Applicants should use a list to compare the geographical location, biological characteristics, and factors before reference interval study analysis of the reference population distribution.
2. Verification of reference intervals
The applicant should select at least 20 reference individuals with similar geographical distribution and demographic characteristics to the population expected to use the applied product, and study the reference of the small sample population with the same pre-analytic factors and the same detection conditions as the original reference interval study. value. Compare the comparability between small sample reference values and original reference intervals. If the reference values of no more than 2 of the 20 reference individuals exceed the original reference interval, the verification is passed and the original reference interval can be used directly. If there are more than 20 reference individuals, the data exceeding the original reference interval does not exceed 10% of the test results, that is, the verification is passed; if more than 10% of the data exceed the original reference interval, at least 20 additional reference individuals should be selected and re-tested. Verify according to the above judgment criteria. If other reference boundary values are used for reference interval verification, the corresponding verification standards must meet statistical requirements. If the verification results meet the requirements, the original reference intervals can be used directly. Otherwise, all analytical procedures should be checked, whether there are biological differences in the samples, and your own reference intervals should be established as described above.
In statistics, as the sample size increases, the ability to use statistical principles to discover differences among populations becomes stronger. Therefore, the applicant can increase the sample size of the reference individuals, such as using 60 samples, and compare the measured reference value with the original reference interval to determine whether the reference value and the original reference interval are comparable.
