Whole-blood hemagglutination inhibition test for Venereal Disease ResearchLaboratory (VDRL) antibodies

Nontreponemal antibody tests such as the Venereal Disease Research Laborato ry (VDRL) test are carried out on serum and widely used as screening tests for syphilis. The aim of the present study was to develop a screening test for syphilis making use of whole blood and VDRL liposomes. Antibody to huma n red blood cells was conjugated to VDRL liposomes and reacted with a dilut ed sample of patient whole blood. A total of 951 samples were tested by the new test and the VDRL tube test. All 49 VDRL samples positive by the VDRL test showed inhibition of hemagglutination in the whole-blood test (sensiti vity, 100%), Of 902 samples with negative results by the VDRL test, 901 cau sed hemagglutination when tested with the liposomes (specificity, 99.9%). T he hemagglutination inhibition method tests for syphilis in a simple one-st ep procedure in which whole blood is added to a tube containing liposomes. The new test has potential for point-of-care testing in developing countrie s.