Surveillance of an infectious syphilis outbreak in south London, UK: a comparison of reporting systems

Rising heterosexual syphilis in south London in 2002 prompted Local Enhanced Syphilis Surveillance (LESS) in five of the 10 genitourinary medicine clinics. LESS reported a fall in heterosexual infectious syphilis in 2004 that was corroborated by the National Enhanced Syphilis Surveillance (NESS). However, mandatory clinic Korner Codes 60 (KC60) coding did not support the reported fall; therefore database discrepancies were evaluated. Three databases (KC60, NESS and LESS) were compared in 2004 at selected clinics using clinical notes as the reference. Six clinics participated in NESS. Four clinics participated in both LESS and NESS and three of these clinics were visited. Only 48% (79 of 163) of KC60 infectious syphilis cases were heterosexual, 36% (58 of 163) were men who have sex with men and the rest were incorrectly coded. The NESS and LESS databases captured 80% and 68% of the confirmed heterosexual syphilis cases, respectively. Despite the inaccuracy in mandatory KC60 returns, this surveillance system captured additional heterosexual syphilis cases.