The CNR external quality assessment program for immunoassays: statistical analysis and reports for participants

The results collected in the CNR/Tecno-standard external quality assessment (EQA) program for immunoassays of hormones and tumor markers are computer-processed to prepare a "periodic" report and an "end-of-period" report to be sent back to the participants in the survey. The aim of the periodic report is to allow comparison between the result obtained by a laboratory on a single EQA sample with those of all the other laboratories and with the users of the same method/kit; the report contains a histogram of all results and the mean, SD, CV, median and range (computed after trimming of outliers). The same statistics are also reported for data grouped according to the method/kit used. The end of period report provide the participant with a scored estimate of individual analytical performance (average bias and average imprecision) achieved assaying all the EQA samples dispatched in the control cycle (usually a six-month period during which 12-18 samples have been assayed); this cumulative report contains estimates of the performance of those kits more widely used in the survey. Beside helping laboratories to monitor their performance against an external reference, the EQA allows the collection of a large amount of data from which the state of the art and trends in the quality of immunoassays can be soundly evaluated and documented. To achieve this aim, the average total variability is computed from all data collected in the EQA cycle; this index is used for comparing the between-laboratory agreement of different immunoassays and for demonstrating trends of the quality over time.(ABSTRACT TRUNCATED AT 250 WORDS)