Hepatitis B surface antigen detection using pooled sera. A cost-benefit analysis.

OBJECTIVES

To examine the feasibility and to perform a cost benefit analysis of a 5-sample pooling strategy using an enzyme immunoassay (EIA) for the screening of hepatitis B surface antigen (HBsAg).

MATERIAL AND METHODS

To assess the sensitivity and specificity of the pooling method, each of the 40 positive sera (from weak to intensely HBsAg-positive) and 250 negative sera were tested in a pool with 4 HBsAg-negative sera. The limit of detection for HBsAg/ad and HBsAg/ay was evaluated using sera from a panel of purified subtypes. A study under real conditions was conducted using pools from 340 pregnant women.

RESULTS

The sensitivity and specificity of this technique were 100%. The correlation coefficient among the sample/cutoff ratios of 40 samples studied in single and in pooled conditions was 0.792 (p < 0.005). The pooling method has lower levels of detection for HBsAg/ad and HBsAg/ay at 0.20 ng/mL and 0.12 ng/mL, and the single method at 0.34 ng/mL and 0.29 ng/mL, respectively. The pooling method loses no sensitivity for values up to 100 IU/L of anti-HBs in the four sera mixed with a positive serum. The cost-benefit analysis showed that the pooling method could save from 30% up to 75% of the cost of HBsAg determination, according to whether seroprevalences were 10% or 1%, respectively.

CONCLUSIONS

The pooled HBsAg EIA yielded no worse than the single EIA test, and was a cost-effective and valid strategy in areas with a high, medium or low prevalence.