Total number invited, respondents, participants and Ct-positives with estimated NNI and NNS per chlamydia case (Ct), per region and per round in the Chlamydia Screening Implementation Programme, 2008–2010
| Amsterdam | Rotterdam | South Limburg | |||||||
| R1 | R2 | R3* | R1 | R2 | R3* | R1 | R2 | R3 | |
| Number invited | 139 919 | 155 796 | 129 359 | 107 806 | 120 793 | 97 498 | 13 269 | 25 214 | 38 428 |
| Number responded† | 30 318 | 23 455 | 15 952 | 20 796 | 15 783 | 10 629 | 2973 | 3825 | 4381 |
| Response rate (95% CI) | 21.7% (21.5 to 21.9) | 15.1% (14.9 to 15.2) | 12.3% (12.2 to 12.5) | 19.3% (19.1 to 19.5) | 13.1% (12.9 to 13.3) | 10.9% (10.7 to 11.1) | 22.4% (21.7 to 23.1) | 15.2% (14.7 to 15.6) | 11.4% (11.1 to 11.4) |
| Number selected by risk score (95% CI) | – | – | – | – | – | – |
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| Number tested | 24 056 | 19 331 | 13 155 | 16 361 | 12 904 | 8594 | 1429 | 1927 | 2149 |
| Participation rate (95% CI) | 17.2% (17.0 to 17.4) | 12.4% (12.2 to 12.6) | 10.2% (10.0 to 10.3) | 15.2% (15.0 to 15.4) | 10.7% (10.5 to 10.9) | 8.8% (8.6 to 9.0) | 10.8% (10.2 to 11.3) | 7.6% (7.3 to 8.0) | 5.6% (3.4 to 5.1) |
| Number chlamydia positive | 836 | 666 | 439 | 832 | 639 | 426 | 73 | 103 | 90 |
| Positivity rate (95% CI) | 3.5% (3.2 to 3.7) | 3.4% (3.2 to 3.7) | 3.3% (3.0 to 3.7) | 5.1% (4.8 to 5.4) | 5.0% (4.6 to 5.3) | 5.0% (4.5 to 5.4) | 5.1% (4.1 to 6.4) | 5.3% (4.4 to 6.4) | 4.2% (3.4 to 5.1) |
| NNI/Ct (95% CI) | 167 (156 to 172) | 234 (219 to 256) | 295 (226 to 384) | 130 (121 to 139) | 189 (175 to 205) | 229 (206 to 300) | 182 (145 to 229) | 244 (206 to 290) | 427 (352 to 519) |
| NNS/Ct (95% CI) | 29 (25 to 33) | 29 (27 to 31) | 30 (24 to 40) | 20 (18 to 21) | 20 (18 to 21) | 20 (15 to 26) | 20 (16 to 25) | 19 (16 to 23) | 24 (19 to 30) |
↵* Amsterdam and Rotterdam had not completed all invitations yet; included were invitations up to December 2010.
↵† Response in Amsterdam and Rotterdam was requesting a test package online; in South Limburg filling-in risk score questionnaire.
NNI, number needed to invite; NNS, number needed to screen; R1, round 1 (2008/2009); R2, round 2 (2009/2010); R3, round 3 (2010).