A comprehensive evaluation of the proficiency testing program for the HIV-1 BED incidence assay

Abstract

The HIV-1 BED incidence assay was developed at the Centers for Disease Control and Prevention and since 2005 has been available as a commercial kit for use in HIV-1 incidence surveillance. A BED-specific proficiency testing (PT) program was initiated in 2006 that included a panel of eight coded specimens (six unique and two duplicates) to participating laboratories. The number of participating laboratories increased from 12 to 38 from 2006 to 2009. Overall, 96.1% of the laboratories reported results, and 95.4% of those reporting achieved a 100% score. The observed mean normalized optical density (OD-n) values of all participants correlated well with the expected OD-n values for all specimens (R(2) = 0.98) used for seven PT rounds. BED testing demonstrated high reproducibility among all laboratories, with an agreement of 99.3% (574/578) between initial and confirmatory classification and regression statistics of R(2) = 0.96, slope = 1.022, and intercept = 0.0066. Reproducibility among duplicate specimens was very high during each PT round, with mean deviation of 1.8%. Analysis of controls and calibrator specimen for all 343 runs showed a coefficient of variation of ca. 20% for raw ODs in the dynamic range, which was reduced to <10% when the OD was normalized (OD-n). Most laboratories that failed the PT assessment had transcriptional errors, kit reagent problems, or specimen handling errors. Thus, the BED-specific PT program enabled us to track performance of different laboratories conducting the BED assay while identifying areas for improvements. This program will also serve as a template for future PT programs for new incidence assays as they become available.

Fig. 1.

Participation and performance of laboratories in the BED-specific PT program over seven rounds.

Fig. 2.

Overall concordance of mean participant results with expected CDC results for 56 specimens examined over seven rounds. The regression line with the best fit is shown (R² = 0.982). Vertical and horizontal arrows indicate 0.8 cutoffs.

Fig. 3.

Reproducibility of the BED assay showing concordance between initial and confirmatory test results. The best-fit regression line is shown with statistics in the lower right portion of the figure. Two specimen results with very divergent initial and confirmatory results are indicated by diamonds (◆).

Fig. 4.

Reproducibility of coded, duplicate specimens sent during each round of PT program. The mean OD-n of all participants is shown for duplicate specimens for all seven rounds.