Estimating the effective rate of sex partner change from individuals with sexually transmitted diseases

Abstract

Background and objectives: The effective rate of partner change is an important variable for determining whether an epidemic of a sexually transmitted disease (STD) occurs. It is essential for understanding the transmission dynamics of STDs.

Goal of this study: The problem of estimating the effective rate of partner change is addressed.

Results: Under certain conditions the mean rate of partner change in STD patients estimates the effective rate of partner change in the general population.

Conclusion: To estimate the effective rate of partner change in a population, the use of surveys of patients with STD provides a simpler and less costly alternative to population surveys of sexual behavior.

PIP: A random sample of sexually transmitted disease (STD) patients can be used to determine the effective rate of partner change. Interviews with STD patients can directly measure the effective rate of partner change in populations with a low prevalence of STDs. Yet, in populations with a substantial STD prevalence, or when immunity exists to STDs, some infective partnerships do not result in STD transmission, because the partner is already infected or immune. This situation would happen most often with partners who frequently change partners. The actual rate of partner change in STD patients would be somewhat lower than the rate in a very low STD prevalence population (i.e., effective rate of partner change). In fact, the prevalence of STDs would have to be very high to have a significant effect on the estimate of the effective rate of partner change. Thus, it is rarely necessary to adjust. If the following conditions are true, the mean rate of acquiring new sex partners in a sample of STD patients is sufficient to estimate the population effective rate of sex partner change: the sample of STD patients must have been randomly selected, in terms of rate of partner change, from all STD incident cases; the STD prevalence rate must be low enough to justify disregarding saturation effects (that is, a low likelihood of an infected person developing a partnership with an already infected person); there must be little or no evident immunity to the STD etiologic agent. Surveys of STD patients are a more simple and less expensive method to estimate the effective rate of partner change in a population than population surveys of sexual behavior.