The sensitivity and specificity of the three laboratory procedures for the serological test for syphilis

ABSTRACT

1. For our purpose, we adopted three serological procedures for the serological test for syphilis, namely the Kahn standard flocculation test, the VDRL slide flocculation test, and the Kolmer complement-fixation test. Our reason for adopting them was to have a representative tube microscopic flocculation test, a slide microscopic flocculation test, and a complement-fixation test2. With the use of the 3 serologic procedures, the samples of sera from clinically diagnosed syphilitics of different stages of the disease gave positive reactions in 96.24 cases, doubtful reactions in 1.88 cases, and negative results in 1.88. Using the Kahn test, the VDRL test, or the Kolmer test individually, we observed doubtful results in 3.27, 2.28 and 9.11 of the cases we obtained negative findings in 3.46, 4.65, and 11.95 of the cases respectively. This shows the advantage of using three serologic procedures over the routine use of one serologic test alone3. Based on our findings, the specificity of the Kahn standard flocculation test is 98.6; th VDRL slid flocculation test is 99.4; and the Kolmer complement-fixation test is 99.9. The sensitivity and specificity of the tests in syphilitics, and even in the different stages of syphilitic infections, are variableOur experience shows that the Kahn standard is the most sensitive, but the least specific. The Kolmer complement-fixation test, on the other hand, is the least sensitive, but the most specific. The VDRL slide-flocculation test stands uniformly halfway between the two, both in sensitivity and specificity. Because of this, we believe that, if one of these three procedures is to be adopted alone, the VDRL slide flocculation test should be given the preference. (Conclusions)