OBJECTIVE: Passive retrospective cohorts composed of persons who have tested 2 or more times for a sexually transmitted infection (STI) of interest during clinical visits have been used to estimate STI incidence. We hypothesized that the analytic period of a passive cohort might affect the estimate of STI incidence, with shorter periods yielding higher estimates of incidences of infection. STUDY: We analyzed data collected from women, 12 to 24 years of age, tested for chlamydia 2 or more times at 6 sites in San Francisco between January 1997 and December 2000. Incidence was calculated for 10 different analytic periods. RESULTS: The calculated incidence of chlamydial infection during 1997 was 16.8 (95% confidence interval [CI], 10.9-24.0) per 1000 person-months of follow up. The calculated incidence dropped markedly as the analytic period lengthened, with the incidence estimated to be 9.7 (95% CI, 8.6-10.9) using a study period of 4 years (1997-2000). Estimates of incidence were similar when using the same analytic period, regardless of calendar year, and there was a similar decline in estimated incidence using longer analytic periods. CONCLUSIONS: Estimates of STI incidence based on passive cohort data may have limited epidemiologic value because incidence measures may be highly dependent on the analytic period.
OBJECTIVE: Passive retrospective cohorts composed of persons who have tested 2 or more times for a sexually transmitted infection (STI) of interest during clinical visits have been used to estimate STI incidence. We hypothesized that the analytic period of a passive cohort might affect the estimate of STI incidence, with shorter periods yielding higher estimates of incidences of infection. STUDY: We analyzed data collected from women, 12 to 24 years of age, tested for chlamydia 2 or more times at 6 sites in San Francisco between January 1997 and December 2000. Incidence was calculated for 10 different analytic periods. RESULTS: The calculated incidence of chlamydial infection during 1997 was 16.8 (95% confidence interval [CI], 10.9-24.0) per 1000 person-months of follow up. The calculated incidence dropped markedly as the analytic period lengthened, with the incidence estimated to be 9.7 (95% CI, 8.6-10.9) using a study period of 4 years (1997-2000). Estimates of incidence were similar when using the same analytic period, regardless of calendar year, and there was a similar decline in estimated incidence using longer analytic periods. CONCLUSIONS: Estimates of STI incidence based on passive cohort data may have limited epidemiologic value because incidence measures may be highly dependent on the analytic period.
Authors: Margot Kuo; Naveed Z Janjua; Ann N Burchell; Jane A Buxton; Mel Krajden; Mark Gilbert Journal: Am J Public Health Date: 2015-06-11 Impact factor: 9.308
Authors: Charlotte A Gaydos; Catherine Wright; Billie Jo Wood; Gerry Waterfield; Sharon Hobson; Thomas C Quinn Journal: Sex Transm Dis Date: 2008-03 Impact factor: 2.830
Authors: Hasina Samji; Jia Hu; Michael Otterstatter; Mark Hull; Troy Grennan; David Moore; Mark Gilbert; Rob Higgins; Jason Wong Journal: PLoS One Date: 2022-01-27 Impact factor: 3.240