Impact of proficiency testing program for laboratories conducting early diagnosis of HIV-1 infection in infants in low- to middle-income countries

Abstract

A voluntary, cost-free external quality assessment (EQA) program established by the U.S. Centers for Disease Control and Prevention (CDC) was implemented to primarily monitor the performance of laboratories conducting HIV Early Infant Diagnosis (EID) from dried blood spots (DBS) in low- to middle-income countries since 2006. Ten blind DBS proficiency test (PT) specimens and 100 known HIV-positive and -negative DBS specimens (to be used as internal controls) were shipped triannually to participating laboratories with reports for the PT specimens due within 30 days. The participant's results and a summary of the performance of all participating laboratories and each diagnostic method were provided after each test cycle. Enrollment in the CDC PT program expanded progressively from 17 laboratories from 11 countries in 2006 to include 136 laboratories from 41 countries at the end of 2012. Despite external pressures to test and treat more children while expanding EID programs, mean PT test scores significantly improved over time as demonstrated by the upward trend from mid-2006 to the end of 2012 (P=0.001) and the increase in the percentage of laboratories scoring 100% (P=0.003). The mean test scores plateaued over the past 10 testing cycles, ranging between 98.2% and 99.7%, and discordant test results still occur but at a rate of no higher than 2.6%. Analysis of these test results suggests a positive impact of proficiency testing on the testing performance of the participating laboratories, and a continuous training program and proficiency testing participation may translate into laboratories improving their testing accuracy.

FIG 1

Mean score over the course of 20 testing cycles. A linear regression for trend was used to analyze for changes in mean score over time from testing cycle 2 in 2006 (2006-2) to 2010-1.

FIG 2

Percentage of laboratories scoring 100% at each test cycle. A linear regression for trend was used to analyze the percentages of laboratories scoring 100% over time.

FIG 3

Percentage of discordant results by all participating laboratories. Discordant results included false-positive (FP), false-negative (FN), and combined equivocal and invalid (Equiv) results. Equivocal results (optical density value between 0.2 and 0.8) were reported only by Roche Amplicor DNA v1.5 users. Invalid results were reported by Cobas AmpliPrep/Cobas TaqMan HIV-1 Qual test users when the Amplilink software reported an invalid result(s) within a run where control values were valid.

FIG 4

Mean scores according to number of laboratories in country at the 2012-3 test cycle. The 41 countries have 1, 2, 3, 4, 5, 8, 10, 11, 14, or 18 laboratories performing DNA PCR for EID. The bubble size corresponds to the number of countries. A linear regression for trend was used to analyze the mean scores per number of laboratories per country.