High frequency of false positive results in HIV screening in blood banks.

BACKGROUND: This study was carried out to determine the frequency of false-positive results during serological screening for the presence of antibodies against HIV-I/2 in blood banks.

METHODS: A cross-sectional study was conducted from January-December 1999 as screening of voluntary non-renumerated blood donor pool for HIV in the public sector blood banks, in all the six divisions of Balochistan. 5000 subjects were screened for the presence of antibodies against HIV-I/ 2. The subjects were all males between the age group 18-50 years, attending the public sector blood banks as non-renumerated blood donors. Strategy 1 was adopted for initial screening. Strategy II and III were observed in retesting on ELISA, as recommended by UNAIDS/WHO for blood banks.

RESULTS: Out of 5000 subjects, 48 (0.96%) were positive for HIV-I/2 on Strategy I, 37 (77% of 48) met the criteria of false positive, while only 11 (0.22% of 5000) were found to be true positive.

CONCLUSION: In blood banks, screening for HIV antibodies is performed for intervention of the positive donations. UNAIDS / WHO Strategy-I is observed on a smaller workload blood banks where donations are less than 20 per day. A high rate of false positive results in serological HIV screening on Strategy-I depicts that the test is highly sensitive but not highly specific. Labeling someone with HIV positive, when actually he is not, forces the health authorities to find other ways of HIV screening in blood banks, which should be much more specific and therefore reliable.