It is hypothesized that sexually transmitted diseases (STDs) increase the risk of HIV acquisition. Yet, difficulties establishing an accurate temporal relation and controlling confounders have obscured this relationship. In an attempt to overcome prior methodologic shortcomings, we explored the use of different study designs to examine the relationship between STDs and HIV acquisition.
Acutely HIV-infected patients were included as cases and compared to 1) HIV-uninfected patients (matched case-control), 2) newly diagnosed, chronically HIV-infected patients (infected analysis), and 3) themselves at prior clinic visits when they tested HIV-negative (case-crossover). We used t-tests to compare the average number of STDs and logistic regression to determine independent correlates and the odds of acute HIV infection.
Between October 2003 and March 2007, 13,662 male patients who had sex with men were tested for HIV infection at San Francisco's municipal STD clinic and 350 (2.56%) HIV infections were diagnosed. Among the HIV-infected patients, 36 (10.3%) cases were identified as acute. We found consistently higher odds of having had an STD within the 12 months (matched case-control, OR 5.2 [2.2-12.6]; infected analysis, OR 1.4 [1.0-2.0]; case-crossover, OR 1.3 [0.5-3.1]) and 3 months (matched case-control, OR 34.5 [4.1-291.3]; infected analysis, OR 2.3 [1.1-4.8]; case-crossover OR 1.8 [0.6-5.6]) prior to HIV testing among acutely HIV-infected patients. We found higher odds of acute HIV infection among patients with concurrent rectal gonorrhea (17.0 [2.6 - 111.4], p<0.01) or syphilis (5.8 [1.1 - 32.3], p=0.04) when compared to those HIV-uninfected.
Acute HIV infection was associated with a recent or concurrent STD, particularly rectal gonorrhea, among men at San Francisco's municipal STD clinic. Given the complex relationship between STDs and HIV infection, no single design will appropriately control for all the possible confounders; studies using complementary designs are required.