Validation of qualitative methods of analysis that use control samples

Qualitative methods are frequently used for screening. In some applications, the resulting positive samples are subsequently analyzed by a suitable quantitative confirmatory method, so it is important that the qualitative assay provides reliable results. Although some validation procedures have been reported in this area, much work is still required because there are many different qualitative methods with many different characteristics. In this report, we examine the different types of control samples used in qualitative analysis that provide instrumental responses, we review the most important quality parameter in the validation process, we propose a procedure for estimating the selected quality parameters - traceability, the unreliability region, sensitivity and specificity rates, and false positive and negative rates - and we show how their values can be calculated in a case study: an ELISA method used in a clinical context.