Evaluation of Thailand national external quality assessment on HIV testing

The Thailand National Institute of Health (NIH) established an external quality assessment (EQA) scheme on HIV serology testing since 1994 for many public health laboratories. For the past six years, the NIH has evaluated the activities of 226 laboratories.

Approximately 40,000 tests using 16 trial samples of external quality assessment panel performed at 226 laboratories during 2000-2006. The methods performed were classified into five assays; machine-based enzyme immunoassay (MBA), microplate-based enzyme immunoassay (EIA), simple/rapid test and antigen assay only performed at blood screening laboratory centers. A few laboratories performed confirmation method by western blot (WB). Most participating laboratories performed at least two methods.

The evaluation showed that, during the six-year period, the program had an increasing response rate among all groups of laboratories: government hospital laboratories, private hospital and clinic laboratories and blood screening laboratory centers. Moreover, there were no significantly different errors found between these groups. The highest median percent of overall errors found was in antigen assay. Very minimal errors appeared on other methods.

National HIV EQA program has played an important role in improving the quality of participating laboratory performance. The participating laboratories gained a better understanding and were able to use good quality anti-HIV approved kits. Furthermore, HIV serology testing selection was varied over the past six years as microplate-based EIA was mostly used in the past but currently MBA and simple/rapid test are more commonly used. The test methods were determined by test volumes and budget. In addition, sensitivity was one critical reason labs chose to use EIA. The most popular method used was simple/rapid testing. Overall errors occurred with all assays but not with WB. Errors could occur with any test techniques if good quality management is not employed.