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Table 1 Numbers in the study and reply and response rate, for each time period, by sampling design

From: Does population screening for Chlamydia trachomatisraise anxiety among those tested? Findings from a population based chlamydia screening study

  Time Period
  Before invitation At invitation After receipt of negative result
  Number sent Number returned (%) Number sent Number returned (%) Number sent Number returned (%)
Questionnaire reply rates a       
Cohort 687 297 (43%) 680 177 (26%) 172 126 (73%)
Cross-sectional 624 250 (40%) 763 241 (32%) 146 101 (69%)
All 1311 547 (42%) 1443 418 (29%) 318 227 (71%)
Analysis response rates b       
Cohort 186 113 (61%) 186 168 (90%) 172 126 (73%)
Cross-sectional 175 105 (60%) 244 229 (94%) 146 101 (69%)
All 361 218 (60%) 430 397 (92%) 318 227 (71%)
  1. a. Denominator: all individuals to whom questionnaires were posted.
  2. Numerator: all those who replied regardless of their chlamydia test result and regardless of their inclusion in the case-control study.
  3. b. Denominator: all individuals with a negative test result and not included in the case-control study.
  4. Numerator: of these individuals, those who responded.