Reactivity in the Venereal Diseases Research Laboratory test and the Mercia IgM enzyme immunoassay after treatment of early syphilis.

The aim of the study was to compare reactivity in the Mercia immunoglobulin M enzyme immunoassay (IgM EIA) and the Venereal Disease Research Laboratory (VDRL) after treatment of 229 previously untreated patients with early syphilis. At three months, the VDRL and the IgM EIA were negative in 41 (38%) and 71 (62%) cases, respectively; a four-fold or greater decrease in VDRL titre occurred in 106 (99%). At six months, the VDRL and the IgM EIA were negative in 45 (48%) and 69 (71%) patients, respectively; a four-fold or greater decrease in VDRL titre occurred in 88 (95%) and an eight-fold or greater decrease in 80 (86%). At 12 months, the VDRL and the IgM EIA were negative in 35 (70%) and 55 (92%) patients, respectively; a four-fold or greater decrease in VDRL titre occurred in 49 (98%) and an eight-fold or greater decrease in 47 (94%). The Mercia IgM EIA is as sensitive as the VDRL in monitoring treatment of primary syphilis but not as sensitive as the finding of a four-fold or eight-fold decrease in VDRL titre in patients treated for secondary or early latent infection.