We reported the development of the BED assay in 2002 (23
), and the assay was commercially available in 2005. Since then, the number of laboratories using the BED assay for incidence surveillance has increased over time. Unlike HIV diagnostic enzyme immunoassays (EIAs), which are qualitative in nature, incidence tests are quantitative antibody assays that require higher precision to ensure that the classification of recent HIV infection is based on validated criteria and is not influenced by variability among laboratories. Since 2006, we have successfully implemented the PT program for the BED assay. Our PT program has helped to monitor the performance of participating laboratories while assessing the reproducibility of the BED assay in the field. Since inception of the program, the participation has increased from 12 laboratories to 38. We observed a high return rate of results (overall, 96.1%), which is most likely attributable to preshipment confirmation of participation. Occasional nonparticipation in the program was due to a lack of kits in the inventory and staff turnover. Because HIV surveillance is a periodic event, BED kits are not regularly purchased and kept in the inventory. Staff turnover is a common problem; therefore, it is important to train additional staff to maintain competency.
Overall, the results have been accurate, with 95.4% of those participating in PT program matching with the expected results (100% score). Our comprehensive analyses of data from seven rounds indicated that the precision and reproducibility of the BED assay were outstanding among multiple laboratories, operators, and kit lots. This was clearly demonstrated by comparison of the mean participant data for each round with the expected results (). Duplicate specimens included in each round of PT showed that reproducibility was high when the mean OD-n values of all participants were compared for duplicate specimens (). Each lot of the BED assay is checked for quality and consistency by the CDC before it is distributed widely to other laboratories by manufacturers, which is reflected in its field performance. In addition, the assay is less prone to variability due to its capture format compared to the earlier, less-sensitive EIA version of the incidence assay.
Since the assay is commercially available, there are more laboratories using the BED assay than those participating in the PT program. This program is voluntary but cost-free; therefore, participation in this program is a nonpunitive opportunity for laboratories to monitor their performance and implement improvement measures. Enrollment in the PT program is expected to increase as more laboratories begin to implement incidence testing. With growth come several challenges, including the high cost of shipping plasma specimens on dry ice. We are looking at alternative approaches, including dried blood, serum, or plasma spots (22
) or dried tube specimens (20
), which would significantly reduce shipping costs because these specimens can be shipped at room temperature. In addition, we are exploring the online submission of results, which should greatly improve data acquisition and analysis.
In conclusion, our PT program is part of a comprehensive quality assurance program for HIV-1 incidence testing and provides an opportunity for laboratories to monitor performance of the BED assay and take corrective actions. Several groups have reported the development of different incidence assays (1
). As these assays become implemented more widely, it will be important to ensure the quality of testing by multiple approaches, including the PT program. The PT program implemented by us should serve as a good template to monitor and improve quality of incidence testing as new assays become available.