Prediction of Chlamydia trachomatis infection: application of a scoring rule to other populations

Sex Transm Dis. 2006 Jun;33(6):374-80. doi: 10.1097/01.olq.0000194585.82456.51.


Background: Active case finding is crucial to reduce transmission and consequences of Chlamydia trachomatis (CT) infections. We previously proposed the use of a prediction rule for CT infection for selective screening of high-risk individuals in a population. To support such an application, the prediction rule needs to be validated in other populations.

Methods: We studied participants aged 15 to 29 years in a population-based study in Amsterdam (n = 1,788) and an outreach screening project among high-risk youth in Rotterdam (n = 172). Validity was indicated by discriminative ability (area under the receiver operating characteristic curve [AUC]) and by calibration, which was visualized in plots and tested with the Hosmer-Lemeshow (H-L) goodness-of-fit test. Cutoffs of predicted risk were examined for their effect on sensitivity and the fraction of participants that would need to be screened.

Results: Discriminative ability was reasonable both for the Amsterdam study (AUC 0.66; 95% confidence interval [CI], 0.58-0.74) and for the Rotterdam study (AUC 0.68; 95% CI, 0.58-0.79). The observed CT prevalence was lower than predicted in Amsterdam (H-L P = 0.02) and nonsignificantly higher in Rotterdam (H-L P = 0.20). By screening 77% of the Amsterdam population, 93% of the cases would have been detected, whereas in the Rotterdam study, no cases would be missed by screening 75%.

Conclusion: The chlamydia prediction rule showed a reasonable external validity in two studies. These findings support the use of the rule as a tool for selective chlamydia screening, although only a limited fraction of participants can be excluded when a high sensitivity is required.

Publication types

  • Evaluation Study

MeSH terms

  • Adolescent
  • Adult
  • Chlamydia Infections / epidemiology*
  • Chlamydia Infections / etiology
  • Chlamydia Infections / transmission*
  • Chlamydia Infections / urine
  • Chlamydia trachomatis*
  • Disease Transmission, Infectious*
  • Female
  • Humans
  • Male
  • Models, Statistical*
  • Netherlands / epidemiology
  • Predictive Value of Tests
  • Probability
  • ROC Curve
  • Sensitivity and Specificity
  • Surveys and Questionnaires
  • Urban Population