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Nearly 10% Screened for Syphilis Test Positive at California HIV Clinic
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53rd ICAAC, September 10-13, 2013, Denver
The researchers concluded that MSM in their HIV population bear a "disproportionately high" burden of syphilis. They argued that "routine syphilis screening is a low-cost intervention that remains cost-efficient at detecting new syphilis cases even when employed at frequent intervals."
The CDC recommends at least annual syphilis testing for HIV-positive MSM [3]. But the VA investigators cite two studies showing that more frequent screening boosts the detection rate of asymptomatic syphilis in HIV-positive MSM [3,4]. And they believe their findings support that recommendation.
Mark Mascolini
Routine syphilis screening at a California VA Medical Center detected infection in nearly 1 in 10 HIV-positive people tested [1]. Primary and secondary syphilis incidence in this population far exceeded rates in the local metropolitan area or throughout California from 2006 through 2010.
A 2010 CDC review reported that syphilis prevalence in the United States fell 90% from 1990 through 2000, then began a relentless climb [2]. In 2010 two thirds of primary and secondary syphilis cases in 44 states involved MSM.
To compare syphilis incidence among HIV-positive people at the VA Medical Center in Loma Linda, California with incidence reported locally and across California, researchers conducted this retrospective chart review of the HIV Clinic Care Registry from 2003 (when routine syphilis screening began) through 2010. They determined how many patients tested positive for syphilis with Rapid Plasma Reagin (RPR) screening. They also compared costs of routine syphilis screening with costs of treating syphilis in their population.
From January 2003 through November 2010, a total of 606 HIV-positive people at the VA clinic had 6567 RPR tests. Screening detected 74 cases of syphilis (1.1% of 6567 tests) in 54 men (8.9% of 606 screened patients). Seventy-one cases (96%) involved MSM. Thirty-two newly diagnosed cases of syphilis involving MSM (45% of 71) were asymptomatic, including 9 (13%) with no history of syphilis. Among the 39 cases of symptomatic syphilis involving MSM, 22 (31% of 71) had no syphilis history.
Of the 54 men with RPR-detected syphilis, 51 (94%) were MSM, 39 (72%) were non-Hispanic white, 8 (15%) were non-Hispanic black, 4 (7%) were Hispanic, and the others Asian or American Indian. Only 7% of syphilis cases were staged as primary, while 27% were secondary, 42% early latent, 8% late latent, and 16% neurosyphilis. From 2003 through 2010, the percentage of HIV clinic patients diagnosed with secondary syphilis dropped from about 1.75% to about 0.75%, while the proportion with early latent syphilis rose from 0% in 2003 to about 2% in 2008, 2009, and 2010.
The number of RPR tests per patient per year climbed from about 1 in 2001 to 2.5 in 2005 then to about 3 in every year from 2006 through 2010. The percentage of HIV clinic patients diagnosed with syphilis jumped from just over 0.5% in 2001 to about 3.5% in 2005 and to more than 4% in 2008 before declining to about 3% in 2009 and 2010.
Primary of secondary syphilis incidence dropped two thirds from 2006 to 2010 among HIV patients at the VA clinic (see list below). But compared with primary or secondary syphilis incidence across the state of California and in the San Bernardino-Ontario metropolitan area, incidence among HIV-positive people attending the VA clinic remained substantially higher from 2006 through 2010:
Primary and secondary syphilis cases per 100,000:
2006: VA 526.3, California 9.4, metropolitan area 4.9
2007: VA 430.6, California 10.5, metropolitan area 4.4
2008: VA 294.1, California 11.4, metropolitan area 7.3
2009: VA 184.7, California 9.8, metropolitan area 5.3
2010: VA 177.6, California 10.8, metropolitan area 7.5
The cost of all syphilis testing during the study period totaled only $1826.22, including $1515.40 for the RPRs alone. The VA team calculated that they spent $20.48 on 89 RPRs to find a single positive case. In contrast, the total cost of treating all syphilis cases came to $8363.28. Treating early latent syphilis cost $1671.10 or $64.27 per case. Treating all latent and neurosyphilis cases cost $4327.77 or $241.26 per case.
The researchers concluded that MSM in their HIV population bear a "disproportionately high" burden of syphilis. They argued that "routine syphilis screening is a low-cost intervention that remains cost-efficient at detecting new syphilis cases even when employed at frequent intervals."
The CDC recommends at least annual syphilis testing for HIV-positive MSM [3]. But the VA investigators cite two studies showing that more frequent screening boosts the detection rate of asymptomatic syphilis in HIV-positive MSM [3,4]. And they believe their findings support that recommendation.
References
1. Fajilan A, Mu A, Wong B, Chau T, Ing M. The cost-effectiveness of routine syphilis screening among HIV-infected patients. 53rd ICAAC. September 10-13, 2013. Denver. Abstract H-1266.
2. Centers for Disease Control and Prevention. 2010 Sexually transmitted diseases surveillance. November 2011. http://www.cdc.gov/std/stats10/toc.htm
3. Bissessor M, Fairley CK, Leslie D, Howley K, Chen MY. Frequent screening for syphilis as part of HIV monitoring increases the detection of early asymptomatic syphilis among HIV-positive homosexual men. J Acquir Immune Defic Syndr. 2010;55:211-216.
4. Branger J, van der Meer JT, van Ketel RJ, Jurriaans S, Prins JM. High incidence of asymptomatic syphilis in HIV-infected MSM justifies routine screening. Sex Transm Dis. 2009;36:84-85.
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