Clustering of seropositivities for sexually transmitted infections.

Background: Serology for different sexually transmitted infections (STIs) is useful for epidemiologic studies on the spread of STIs in different populations. Studying whether seropositivities for different STIs cluster could be useful, both for development of improved serologic markers of sexual behavior in populations and for understanding how STIs may differ in terms of the dynamics of their spread.

Goal: To evaluate the degree of clustering of different STIs in relation to sexual history.

Study Design: An age- and sexual history-stratified subsample of 275 women from a survey of healthy Swedish women seeking contraceptive advice was tested for human papillomavirus (HPV) types 6, 11, 16, 18, and 33; Chlamydia trachomatis; herpes simplex virus 2 (HSV-2); and human herpesvirus 8.

Results: Significant clustering was observed only for HPV types 6 and 11; for HPV types 16, 18, and 33; and for C trachomatis and HSV-2. The serologic marker that correlated best with lifetime number of sex partners was HPV type 16 (odds ratio [OR], 10.2; 95% CI, 3.8-27.6). The combined serologic marker that correlated most highly with sexual history was joint positivity for HPV types 16 and 33 (OR, 25.5; 95% CI, 5.4-120.4).

Conclusions: The degree of clustering between different STIs varies from nonexistent to strong, implying that different STIs commonly have very different transmission dynamics. Certain combinations of STI serologic tests may be useful in epidemiologic studies for predicting sexual behavior in groups.