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Table 1 Power calculation per outcome variable

From: The Netherlands Chlamydia cohort study (NECCST) protocol to assess the risk of late complications following Chlamydia trachomatis infection in women

  Expected cumulative prevalence in 2022 Number of samples needed for 80% power Expected power with samples size N = 6600
  CT pos. History CT neg. History CT pos. History CT neg. History CT pos. History (n = 1700) CT neg. History (n = 4900)
PID 7.7% 1.1% 63 195 >99%
Ectopic pregnancy 1.8% 0.9% 1415 4385 85%
Tubal factor subfertility 1.3% 0.2% 401 1241 >99%
  1. Expected cumulative prevalence of PID, ectopic pregnancy and tubal factor subfertility was based on age distribution per outcome in the primary care database from the Netherlands Institute for Health Services Research (NIVEL – PCD) and the expected age distribution in NECCST in 2022 by CT status. Here from we derived the samples size, with 80% power, a significance level of 5% and a 1 to 3 exposed/unexposed ratio, per outcome in the CT-positive history and negative history group in 2022 ( CT Chlamydia trachomatis infection, PID pelvic inflammatory disease