Background:  The AACTG Pharmacology Laboratory Network has implemented a comprehensive quality assurance program including assay validation procedures, quality control monitoring and a proficiency testing program. Proficiency testing includes both adult (n = 6) and pediatric (n = 5) pharmacology laboratories.

Methods: Two (2) rounds of proficiency testing samples have been distributed by the program. Samples were prepared in blank EDTA plasma and in duplicate (independently spiked) in two ACTG laboratories. The first round (July 2001) included low and intermediate levels for protease inhibitors (PIs): indinavir (IDV), saquinavir (SQV), nelfinavir (NFV), ritonavir (RTV); and non-nucleoside RT inhibitors (NNRTIs): nevirapine (NVP), efavirenz (EFV). The second round (February 2002) consisted of low, intermediate and high levels of each drug with the addition of amprenavir (APV). Weighed-in drug amounts were target values unless the mean of the group was > 5% deviation from the weighed-in value, then the mean of the group value was taken as the target value. Laboratory performance was satisfactory if drug concentration were within 20% deviation of the target value.

Results: Combined results for 2 rounds indicate the following percentage of samples within the accepted range: IDV: 74/84 (88%); SQV: 63/64 (98%); NFV: 84/89 (94%); RTV: 78/82 (95%); APV: 23/24 (96%); NVP: 49/49 (100%); EFV: 65/65 (100%). Overall performance was good with an average of 89.5% satisfactory results for all drugs. The best results were seen with NNRTIs (100% satisfactory results). For PIs an improvement was noted from 90.8% in round #1 to 94.5% in round #2.

Conclusions: The data indicate that a proficiency testing mechanism is in place that will ensure quality pharmacologic data from trials in which assay results are generated in more than one laboratory. Results that are outside of the accepted range are communicated to the respective laboratory for further investigation and corrective action. The program will continue on a twice-yearly basis with additional drugs added as indicated.