IVD quality research, some common requirements!
The quality research of in vitro diagnostic reagents is one of the important contents of product research and development, and it is also a key part of the technical review. The results of quality research are an important basis for formulating product standards. At the same time, part of the content will also be included in the instruction manual to help inspectors and clinicians use it correctly and accurately judge test results.
Diagnostic reagent products involve a wide range of disciplines, rapid technological development, and diverse varieties. The quality research work on different types of products not only has the same common requirements, but also needs to focus on certain aspects based on the characteristics of the products. Let’s share some opinions on some common issues in this research work, with a view to communicating with developers.
1. Several issues that need to be considered in quality research work
1. The contents of quality research for different products such as qualitative measurement, quantitative measurement, and blood typing products are not exactly the same. Developers should analyze specific issues in detail. The content of quality research should be as comprehensive as possible, including both general and targeted projects. At the same time, multiple batches of products must be used for quality research to improve the reliability of product quality research results.
2. Use patient-derived samples or sample pools for quality studies whenever possible. Adding samples or quality controls or standards can supplement quality studies, but it is not recommended to use these samples as the only matrix for quality studies because these samples may not be able to fully evaluate the performance indicators of the product.
3. Use the test methods recommended to users in the product instructions for use as much as possible, including sample processing (such as cell lysis, extraction and centrifugation, etc.), quality control and calibration procedures, etc. for quality research, so as to reflect the expected performance of the product.
4. It is recommended to explain the quality research methods in detail so that the quality research results can be correctly understood. For example, when referring to relevant literature on NCCLS, it is recommended to indicate the cited literature and what modifications have been made.
5. If additive samples are used in quality studies, it is recommended to provide detailed information about the additives such as purity, concentration, etc.
6. If different types of samples are used as the tested objects, such as serum, whole blood, etc., it must be confirmed that there is a high correlation between the measurement results of different types of samples.
2. Methodological verification and inspection in quality research work
Methodological verification and inspection are tasks that all in vitro diagnostic reagent quality research institutes must carry out. Methodological verification and inspection work generally include: precision, measurement range, sensitivity, specificity, accuracy, comparison with similar products or other methods, sample storage and processing conditions, etc.
1. Precision
1.1 It is recommended to use at least three concentrations of samples for precision studies. It is advisable to choose a sample concentration that is medically decisive.
1.2 In order to evaluate the precision of all test steps, the impact of sample pretreatment methods (such as nucleic acid extraction, etc.) should be evaluated, that is, sample pretreatment should be performed separately for each repeated test.
1.3 It is recommended to study the NCCLS EP05-A document, which provides a detailed description of experimental design, sample selection, statistical methods, etc.
2. area
2.1 It is recommended to use at least 5 concentration samples within the measurement range to conduct research on the measurement range. The sample concentrations should be evenly distributed throughout the entire measurement range of the kit. It is recommended that samples of each desired concentration be pretreated separately to evaluate the impact of pretreatment on the assay range.
2.2 Some immunological reagents have a "HOOK effect". It is recommended to expand the concentration range used in the measurement range study to the highest clinical concentration to evaluate whether there is a HOOK effect.
2.3 If it is recommended to dilute samples beyond the determination range, the dilution method should be studied and evaluated.
2.4 It is recommended to study the NCCLS EP06-A document. This document provides a detailed description of the sample preparation protocol, sample distribution, experimental methods, statistical methods and evaluation methods.
3. Sensitivity
3.1 Sensitivity refers to the minimum amount of the measured substance that the method can detect, while clinical sensitivity refers to the proportion of diseased people that the method can correctly detect. Analytical sensitivity studies need to be carried out in quality studies.
3.2 It is recommended to perform sample pretreatment on each tested sample separately, which not only simulates the actual experimental method of patient samples, but also evaluates the impact of sample pretreatment on detection sensitivity.
3.3 The measurement deviation and precision should be evaluated at the detection sensitivity level to illustrate the precision requirements that the detection sensitivity can meet.
3.4 For qualitative measurement products, high-concentration samples can be diluted, and the highest dilution factor is used as the detection sensitivity.
3.5 It is recommended to study the NCCLS EP17-P document.
4. Specificity
4.1 Analytical specificity refers to the ability of the method to measure only a certain analyte, and clinical specificity refers to the proportion of people without disease that the method can correctly detect. Studies of analytical specificity are required in quality studies.
4.2 When analyzing specific studies, it is recommended to consider influencing factors in the following aspects:
(1) The sample contains endogenous compounds that may affect detection specificity: such as bilirubin, blood esters, hemoglobin, etc. in blood samples. Urine sugar, urine protein, etc. in urine samples.
(2) Compounds with similar structure to the tested substance: such as methamphetamine detection kit, structural analogs include ephedrine, amphetamine, MDEA, MDMA, ranitidine, procaine, and norepinephrine hydrochloride , codeine, fentanyl alcohol, morphine, etc. For example, HCG assay kit, structural analogs include FSH, LH and TSH, etc.
(3) Microorganisms with similar classification positions or clinical infection sites, such as hepatitis C virus core antigen detection kits. Viruses with similar classification positions or clinical infection sites include CMV, EBV, HIV, HSV, HTLV, HAV, HBV, etc. .
(4) Anticoagulants and preservatives in contact with the sample: such as EDTA, etc.
4.3 It is recommended to study NCCLS Document EP07-A.
5. Accuracy
For quantitative measurement products, methods such as measurement of international or national standards and addition of recovery tests can be used to evaluate the measurement accuracy of the product.
6. Comparative test with similar products or other methods
6.1 The comparative test conducted in the quality research stage is a small-sample clinical study conducted by the developer within the R&D unit. The results are an important basis for whether the product can be used for real large-sample clinical studies. Therefore, the scientificity and standardization of comparative test methods are the basis and guarantee for scientific and reliable test results, and are also an important basis for the success of clinical research on this product.
6.2 Comparative tests conducted in the quality research stage pay more attention to the planning of the test: emphasizing a full understanding of the comparison reagent (contrast method) to be used and the sample to be tested. Emphasize the rationality of sample allocation, because comparative test results on different groups of samples may lead to different test conclusions. Taking quantitative measurement products as an example, you should understand the methodology of the comparison reagent, the purpose and scope of clinical use, the main quality indicators, such as detection sensitivity, quantitative measurement range, measurement precision, traceability of standards (calibrators), and recommended references. value (reference range), etc. For the samples to be tested, various samples that may be encountered in routine work should be included as much as possible, such as samples of diseases, related diseases, hemolysis, lipemia, jaundice, etc., and the concentration of the tested substance should be evenly distributed within the measurement range. The detailed clinical information of the patients being tested should be fully understood in order to conduct a comprehensive analysis of the test results.
6.3 For quantitative determination of products, it is recommended to study NCCLS Document EP09-A2. For qualitative measurement products, the above-mentioned documents can also be referred to in terms of experimental design, sample selection principles, etc.
7. Sample storage and processing conditions
It is recommended that the sample storage times, conditions, etc. recommended by the instructions, including temperature and the number of freeze/thaw cycles allowed, be studied to establish acceptable standards for sample storage and processing conditions.
Different types of products require researchers to conduct targeted research based on their characteristics. It is recommended that developers strengthen their study of the NCCLS series of guidance documents. At present, some sponsors have adopted the methods recommended in the NCCLS document to conduct quality studies and incorporated their research results into the instructions for use.
