Evaluation of two techniques (RPHA and latex agglutination) for use as a screening tool for HBsAg.

RPHA and latex agglutination are two cost effective techniques available for HBsAg screening in our country. Most of the blood banks and other clinical laboratories use RPHA technique or latex agglutination test for screening of donors or patients positive for Hepatitis B surface Ag (HBsAg). All the reagent kits available in the Indian market do not give the ranges of specificity, sensitivity and predictive values for the particular test. Also no data is available if they were tested on Asian sera. Therefore it was decided to evaluated the two most often used techniques RPHA and latex agglutination for their sensitivities and efficacy as a screening test. Our results indicate that though RPHA may be used in a diagnostic set up, it is a poor screening tool as it gives a fairly large number of false negatives and has a low sensitivity. Latex agglutination on the other hand, does not give any false negative results and is recommended for preliminary screening, wherever cost is a constraint. The sera with positive results should be subsequently tested by EIA to rule out the false positive results.