EQUAL-quant: an international external quality assessment scheme for real-time PCR.

Background: Quantitative gene expression analysis by real-time PCR is important in several diagnostic areas, such as the detection of minimum residual disease in leukemia and the prognostic assessment of cancer patients. To address quality assurance in this technically challenging area, the European Union (EU) has funded the EQUAL project to develop methodologic external quality assessment (EQA) relevant to diagnostic and research laboratories among the EU member states. We report here the results of the EQUAL-quant program, which assesses standards in the use of TaqManTM probes, one of the most widely used assays in the implementation of real-time PCR. Methods: The EQUAL-quant reagent set was developed to assess the technical execution of a standard TaqMan assay, including RNA extraction, reverse transcription, and real-time PCR quantification of target DNA copy number.