Estimated number and cost of pelvic inflammatory disease (PID) cases prevented by a single chlamydia test over 12 months for 414 345 sexually active women aged 16–24 years in London with different prevalences of chlamydia and different rates of screening
| Assumed chlamydia prevalence | Number of women aged 16–24 y screened | Number of chlamydia positive women | Expected PID cases over 12 months in unscreened women with chlamydia (8.8%) | Assumed screen coverage | Expected PID cases over 12 months in screened women with chlamydia (1.5%) | Preventable PID cases Risk difference (7.3%, 95% CI –0.82 to 16.5)† | Total preventable PID-associated healthcare costs (at £163 per case)* | |
| National Survey of Sexual Attitudes and Lifestyles 2000* chlamydial prevalence | 3% | 414 345 | 12431 | 1094 | 100% | 187 | 908 (−102 to 2052) | £148 004 (−£16 626 to £334 476) |
| NCSP 2009 chlamydial prevalence | 6% | 414 345 | 27261 | 2399 | 100% | 409 | 1990 (−224 to 4498) | £324 370 (−£36 512 to £733 174) |
| NCSP 2009 6% chlamydial prevalence and 21.5% coverage | 6% | 89 084 | 5345 | 471 | 21.5% | 81 | 391 (−44 to 882) | £63 733 (−£7172 to £143 766) |
| NCSP 2010* expected 39% coverage | 6% | 161 595 | 9696 | 853 | 39% | 146 | 708 (−80 to 1600) | £115 404 (−£13 040 to £260 800) |