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Prospective evaluation of a flow chart using a risk assessment for the diagnosis of STDs in primary healthcare centres in Libreville, Gabon.

BACKGROUND
The serious impact of STDs on women and children in particular, and the linkage between STDs and HIV infection are a profound concern to public health worldwide. One of the main strategies against STDs is based on early diagnosis and treatment. However, this approach is limited by the lack of appropriate laboratory facilities. A syndromic approach has been recommended by the WHO but needs to be evaluated under field conditions. A preliminary cross sectional study on STD prevalence and risk factors in Libreville showed that 13.5% of pregnant women had gonococcal and/or chlamydial infection which justifies systematic screening of STDs. Based on the results of this study, different flow charts with or without a risk factor assessment (score) were designed. The flow chart with the best performances for diagnosing chlamydial or gonococcal cervical infection and routinely acceptable, was a score algorithm, based on two risk factors (age and marital status) and four simple clinical signs (pelvic or lumbar pain, vaginal discharge and its characteristics). Sensitivity and specificity were 76.9% and 40.4% respectively. Thus, the objective of this study was to evaluate this strategy under field conditions.


METHODS
A prospective study among pregnant women attending antenatal clinics was done. The score was applied to each woman by a midwife and a physician, and specimens were collected for the reference laboratory tests. Validation of the algorithm was done by comparing the performances with the gold standard laboratory diagnosis.


RESULTS
646 pregnant women were enrolled. The prevalence of cervical infection was 11.3. The sensitivity and specificity of this algorithm recorded by the midwives were 73.3% and 54.8%, respectively and by the physician 76.7% and 50.6%. The proportion of women correctly classified by the midwives and by the physician was not significantly different.


CONCLUSION
The score applied was well accepted by healthcare workers and patients, and was routinely practised. Results obtained by the midwives and by the physician were similar. Thus, the use of flow charts which adds a risk assessment to the syndromic approach for diagnosing cervical infections is feasible. However, the performances of such flow charts need to be improved before being used routinely.