Re-emerging syphilis in gay men: a case-control study of behavioural risk factors and HIV status

Abstract

Of 58 diagnosed cases of syphilis in Greater Manchester (May 1999 and August 2000), 38 were approached through genitourinary medicine clinics to participate in a structured interview regarding their sexual, social, and drug using behaviour during 12 months before syphilis diagnosis. Characteristics of the 27 people (71.05% compliance) who agreed to participate were 96.30% male, 85.18% homosexual, and 25.93% previously having been diagnosed HIV positive. All cases had tested positive for syphilis using a Treponema Pallidum Haemagglutination Assay and were in either primary (n=22) or secondary (n=5) stages of the disease. For sex, sexuality and HIV cases were representative of the outbreak to date. Controls were recruited (December 1999 to August 2000) for only homosexual individuals (n=23), as heterosexual cases were considered too few for analysis. Most controls were contacted through gay and HIV voluntary groups (compliance 44 of 85 contacts) with a further 18 controls recruited directly within known gay social areas (compliance 18 of 42 contacts). Controls were selected to provide an overall match for the age, sex (all male), area of residence (first part of postcode), sexual preference (all homosexual) and ethnic characteristics (all white) of the case group. For the purposes of analysis, cases and controls are separated into HIV positive and negative groups (table 1). Comparisons between these four groups use χ² and Mann-Whitney U tests. Overall case-control comparisons use stratified (by HIV status) χ² and a multifactor extension of the Kruskal-Wallis test.³