Co-infection rate of chlamydial urethritis in patients with gonorrhea in Hong Kong

Background: Both gonorrhoea and chlamydia urethritis present with dysuria and discharge. It is difficult to differentiate by history and clinical examination alone. Empirical treatment may induce drug resistance whereas complications and the spread of infections may be increased if treatment is started only after the availability of gonococcal culture and chlamydia polymerase chain reaction (PCR) results that take around few weeks. A study to determine the co-infection rate will help to streamline the treatment strategy. Objectives: The objectives are to determine (1) the co-infection rate of chlamydia among patients with gonorrhoea and (2) their independent risk factors. Methods: All available patients' records who attended the Social Hygiene Clinics of the Department of Health, Hong Kong with urogenital (urethral/cervical) smear done during July 2005 to June 2008 were reviewed. For patients having positive N. gonorrhoeae cultures, concomitant chlamydia PCR results were reviewed to determine the co-infection rate. Results: The chlamydia co-infection rate with gonorrhoea was 22.2% (95% CI=20.7%-23.7%) in which female, younger age (≤25 years) and lack of condom use were the independent risk factors of co-infection. Conclusions: Using a simple and cost-effective diagnostic tool of Gram stain and microscopy together with the knowledge of the co-infection rate of chlamydia among gonorrhoea patients in this retrospective study, empirical treatment should be considered to cover both gonococcal and chlamydial urethritis particularly in high-risk groups such as female patients, young age groups and those not using a condom.