THE ITALIAN QUALITY-CONTROL STUDY FOR EVALUATION OF CD4 CELLS IN CENTERS INVOLVED IN THE TREATMENT OF HIV-1 PATIENTS

We report on the experience of establishing a national network for a q uality control programme in evaluating CD4 cell counts in most Italian centres involved in the care of patients with HIV disease. The 68 cen tres were divided according to their geographical location into eight groups, and twice a year (tests A and B) they received three coded who le blood samples (two were replicates of the same sample) obtained fro m two informed HIV+ patients, one with CD4 counts/mm(3) expected to be <200 and one with values > 300. The medians of the determinations per formed by the labs involved in each of the eight areas were taken as t he 'true' values for each sample. Unsatisfactory performances for perc entage of CD4 cells were identified as a CD4 analysis with residual va lues greater than or equal to +/- 5% and with deviates greater than or equal to +/- 2. For absolute numbers of CD4 cells, an unsatisfactory performance was defined as CD4 counts with residual > +/- 100 CD4 cell s/mm(3) and with deviates greater than or equal to +/- 2. The residual value is the CD4 value reported by each lab minus the median value. T he deviate is the residual divided by the modified interquartile range (IQR x 0.75). Most of the centres provided reliable results. However, some labs failed to provide satisfactory results for percentages (6.2 5% of the tested labs for test A and 6.17% for test B) or absolute num bers (16.25% test A and 12.34% test B). Only 3.7% of the labs gave uns atisfactory results in both tests. Four of the unsatisfactory results from the two tests gave an error in absolute numbers > +/- 200 CD4 cel ls/mm(3). Our data suggest that most Italian labs provide reliable res ults in evaluating the numbers of CD4 cells in HIV-1(+) samples, but t he importance of running a quality control programme is highlighted by our experience with those centres which provide unsatisfactory data w hich may lead to incorrect classification of the patients or assessmen t of treatment.