Initial serological reactions in infectious syphilis.

Each new flocculation test for syphilis is designed to meet the need for a test which can be standardized, reproducible, rapidly and simply performed, and characterized by acceptable sensitivity and specificity. Sensitivity of a test refers to the ability to react in the presence of the disease, i.e. syphilis; specificity refers to the ability not to react in the absence of the disease. Harris, Rosenberg, and Del Vecchio (1948) demonstrated that the VDRL slide test fulfils these criteria. The VDRL test has a high level of sensitivity, with false negative reactions occurring only in the first few days of the primary stage and in some very late cases which have spontaneously become sero-negative (Olansky, Harris, Cutler, and Price, 1956). The specificity, as measured by the percentage of false positive reactions, depends upon the prevalence of syphilis in the community (Nicholas and Beerman, 1965). Recently, Moore and Knox (1965) estimated that less than 3 per cent. of reactive results with the VDRL test are non-specific. Non-treponemal tests have three uses in the control of syphilis: (1) As a screening device to detect persons in need of further diagnostic procedures. (2) To confirm a clinical diagnosis of syphilis. (3) To measure a patient's response to treatment. Quantitative results may increase the usefulness of a test in each of these areas. Such quantitative results may be helpful in distinguishing between false positive reactions and actual cases of syphilis. Among 200 false positive reactors reported by Fiumara (1963), only one individual had serum reactive in a dilution as high as 1:16 in the Hinton test. The quantitative non-treponemal tests are most commonly used as a yardstick by which to measure a patient's response to treatment. The usefulness of the test depends upon its ability to detect changes in the reactivity of the serum; however, the test is not always carried to an end-point titre. Sera reactive initially in only the lowest dilution of serum could not exhibit the same decrease in titre after treatment as sera reactive initially at higher titres. Similarly, a rise in titre due to re-infection or relapse would be difficult to detect in patients whose serum was initially reactive at the highest dilution performed. It is generally accepted that the reactivity of the serum varies with the stage of syphilis. Olansky (1961) states that titres are higher in secondary syphilis than in primary disease and are usually low or moderate in latent syphilis. The present study was designed to increase available information concerning the extent of the difference in reaction to quantitative serological tests in relation to the stage of infectious syphilis, and to determine any differences in result based on age, sex, or race of the patients.