RESUMO
BACKGROUND: The number of people infected with human immunodeficiency virus (HIV) continues to grow globally. Because HIV infection can be transmitted not only by sexual contact but by transfusion, the performance of diagnostic tests can not be overemphasized. However, sometimes false positive results accompanied by high sensitivity of screening tests can confuse both doctors and patients. The present study determined the positive and false positive rates from a large data set. METHODS: From May 2005 to Dec 2008, HIV screening tests were performed with samples obtained from 77,562 patients by ADVIA Centaur (Bayer Health Care LLC, Tarrytown, NY, USA). Positive samples were referred to the Seoul Research Institute of Public Health and Environment for Western immunoblot (WIB) assays. Medical records were reviewed in patients with false positive screening results. RESULTS: The number of patients with a positive screening test was 117 of 77,562 (0.15%). Among these, 56 were positive with WIB (0.07%), producing a positive predictive value for the screening test of 47.9% (56/117). Diagnoses of patients with false positive results were mainly inflammatory diseases such as chronic hepatitis, renal failure, tuberculosis and sexually transmitted diseases. Also, 12 healthy persons referred for regular medical checkup produced false positive RESULTS. CONCLUSION: Positive rates of HIV tests and diagnoses relevant with false positive screening RESULTS could provide useful information to medical personnel for diagnosis and consultation of HIV infection.