Table 3

Implications of using the prediction rule for screening for C trachomatis

Cut off sum score*Sensitivity†Specificity‡Fraction positive¶PPV§
*Selection criterion for screening.
†Percentage of detected chlamydial infections among our study participants when screening under the given selection.
‡Percentage of chlamydia negative participants who would not be screened justly.
¶Percentage of the total population that is eligible for screening under the given selection.
§Prevalence in the screened population (predictive value of selection criterion).
⩾0100.0%0.0%100.0%2.3%
⩾1100.0%0.5%99.5%2.4%
⩾2100.0%2.4%97.7%2.4%
⩾3100.0%4.6%95.5%2.5%
⩾499.3%14.4%85.9%2.7%
⩾594.4%23.0%77.4%2.9%
⩾693.1%38.3%62.4%3.5%
⩾786.8%56.0%45.0%4.5%
⩾879.2%68.4%32.7%5.7%
⩾959.0%83.2%17.8%7.8%
⩾1041.7%92.2%8.6%11.4%
⩾1127.8%96.8%3.7%17.5%
⩾1211.8%98.9%1.4%20.5%
⩾134.2%99.8%0.3%31.6%
⩾141.4%99.9%0.1%25.0%