Article Text
Abstract
Objective To develop and validate a risk scoring tool to identify those who are at increased risk of chlamydia infection.
Methods We used demographic data, sexual behaviour information and chlamydia positivity results from more than 45 000 individuals who attended Sydney Sexual Health Centre between 1998 and 2009. Participants were randomly allocated to either the development or internal validation data set. Using logistic regression, we created a prediction model and weighted scoring system using the development data set and calculated the odds ratio of chlamydia positivity for participants in successively higher quintiles of score. The internal validation data set was used to evaluate the performance characteristics of the model for five quintiles of risk scores including population attributable risk, sensitivity and specificity.
Results In the prediction model, inconsistent condom use, increased number of sexual partners in last 3 months, genital or anal symptoms and presenting to the clinic for sexually transmitted infections screening or being a contact of a sexually transmitted infection case were consistently associated with increased risk of chlamydia positivity in all groups. High scores (upper quintiles) were significantly associated with increased risk of chlamydia infection. A cut-point score of 20 or higher distinguished a increased risk group with a sensitivity of 95%, 67% and 79% among heterosexual men, women and men who have sex with men (MSM), respectively.
Conclusion The scoring tool may be included as part of a health promotion and/or clinic website to prompt those who are at increased risk of chlamydia infection, which may potentially lead to increased uptake and frequency of testing.
- Chlamydia infection
- risk prediction
- hepatitis C
- HIV
- HIV testing
- homosexuality
- infectious disease
- epidemiology
- sexual medicine
- health informatics
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: http://creativecommons.org/licenses/by-nc/2.0/ and http://creativecommons.org/licenses/by-nc/2.0/legalcode.
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Supplementary materials
Supplementary Data bmjopen-2010-000005
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Footnotes
To cite: Wand H, Guy R, Donovan B, et al. Developing and validating a risk scoring tool for chlamydia infection among sexual health clinic attendees in Australia: a simple algorithm to identify those at high risk of chlamydia infection. BMJ Open 2011;1:e000005. doi:10.1136/bmjopen-2010-000005
Competing interests None.
Contributors HW implemented the study, analysed the data and wrote the first draft. RG, BD and AM helped interpreting the data and finalising the manuscript. All authors saw and approved the final manuscript.
Provenance and peer review Not commissioned; externally peer reviewed.