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CDC HIV/AIDS/Viral Hepatitis/STD/TB Prevention News Update
The Value of Screening for Sexually Transmitted Diseases in an
Thomas A. Farley; Deborah A. Cohen; Shin-Yi Wu; Ceryl Lynn
October 27, 2003
Journal of Acquired Immune Deficiency Syndromes (08.15.03)

CDC recommends STD screening among HIV-positive patients. STDs facilitate the spread of HIV, so the diagnosis and treatment of curable STDs in HIV-infected persons can help prevent the spread of HIV to partners even when infected persons continue unprotected sex. However, according to the authors, such screening is not widely practiced in US HIV clinics.

To examine the potential benefits of an STD screening program in a public HIV clinic in New Orleans, the researchers analyzed the results of a urine-based screening for gonorrhea and chlamydia among HIV-positive patients and compared the positivity rates to the prevalence in the local community's general population. To project the potential value of the screening, the investigators estimated the number of potential HIV infections among sex partners that treatment of gonorrhea and chlamydia infections prevented.

For the study period from October 1998-June 2001, researchers found 1.7 percent of those tested for gonorrhea (46/2,629) to have it, and 2.1 percent (56/2,629) of those tested had chlamydia. Test positivity did not vary greatly by race or sex, although African-American women had higher rates of chlamydia (3.5 percent) than white women (1.9 percent), African- American men (1.2 percent) or white men (1.2 percent). But test positivity declined sharply with age: the percentage of patients with gonorrhea fell from 4.8 percent among 15- to 19-year-olds to 1.2 percent among those older than 35. Chlamydia rates fell from 9.5 percent among 15- to 19-year-olds to 0.9 percent among persons older than 35. Still, all age groups tested showed some infections.

Among 18- to 29-year-olds, test positivity for gonorrhea was similar in the HIV clinic to positivity for members of the sociodemographically similar community (3.1 percent versus 2.4 percent). Test positivity for chlamydia in that age cohort was lower among HIV patients (5.4 percent versus 10.5 percent). Based on a previously developed mathematical model, the authors estimated that treatment of all 46 gonorrhea and 56 chlamydia infections in the HIV clinic may have averted 9 HIV infections among sex partners and saved a great deal more in future medical costs than the cost of the screening.

The authors pointed out that implementation of the STD screening program demonstrates the feasibility of routine screening in HIV clinics. That positivity rates approximated those of a sociodemographically matched general population "suggests that HIV-infected persons in care continue to practice high-risk sexual behavior, perhaps at about the same level as the general population," the investigators speculated. The study notes that the mathematical model suggests the even with a relatively low prevalence of gonorrhea and chlamydia among the HIV-infected, screening and treatment of such infections in HIV clinics may prevent a large enough number of HIV infections to be worthwhile.

"In conclusion," the authors noted, "this study supports the CDC recommendation that screening for gonorrhea and chlamydia infection should be established in HIV clinics as part of routine care, at least in geographic areas with higher rates of these STDs. Patients in these clinics found to have these or other STDs can be intensively counseled to reduce risky sexual behavior, their curable STDs can be easily treated, and confidential partner notification procedures initiated. Thus STD screening can initiate a series of actions with the potential to prevent HIV transmission to others."