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Chlamydia Rapid Test was moderately accurate for diagnosing Chlamydia infection in women

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H H Lee

Dr H H Lee, University of Cambridge, Cambridge, UK; hl207{at}cam.ac.uk

QUESTION

Is Chlamydia Rapid Test accurate for screening for and diagnosing Chlamydia trachomatis infection in women?

METHODS

Design:

blinded comparison of Chlamydia Rapid Test with polymerase chain reaction (PCR) testing.

Setting:

young people’s sexual health centre (site 1) and 2 genitourinary medicine clinics (sites 2 and 3) in the UK.

Participants:

1349 women ⩾16 years of age who had not taken antibiotics in the previous month, were not currently menstruating, and provided valid samples (93% of eligible participants). Most women at site 1 (n = 663, mean age 19 y) were asymptomatic; about 67% of women at the genitourinary medicine clinics (n = 385, mean age 25 y at site 2; n = 301, mean age 28 y at site 3) were symptomatic (vaginal discharge or lower abdominal pain).

Description of tests:

Chlamydia Rapid Test (an immunoassay-based test that detects chlamydial lipopolysaccharide) was done on-site by trained clinic staff on self-collected (all sites) and clinician-collected (sites 2 and 3) vaginal swabs. Results were available in about 30 minutes.

Diagnostic standard:

PCR testing for chlamydial DNA was done on first-void urine samples by an independent laboratory. In the case of discordant results, a transcription-mediated amplification assay was done on the urine sample by a second laboratory.

Outcomes:

sensitivity, specificity, and positive (+LR) and negative (−LR) likelihood ratios for detecting Chlamydia infection.

MAIN RESULTS

The prevalence of C trachomatis infection by PCR testing was 8.4% at site 1, 9.4% at site 2, and 6.0% at site 3. Diagnostic test characteristics did not differ by site or type of sample (table). Sensitivity of the test in asymptomatic women was 81%, similar to that for the entire study population.

Diagnostic characteristics of Chlamydia Rapid Test in vaginal swab samples compared with polymerase chain reaction test in first-void urine samples for identifying Chlamydia trachomatis infection in women*

CONCLUSION

Compared with polymerase chain reaction testing, Chlamydia Rapid Test had moderate sensitivity and good specificity for screening for and diagnosing Chlamydia infection in women.

ABSTRACTED FROM

Mahilum-Tapay L, Laitila V, Wawrzyniak JJ, et al. New point of care Chlamydia Rapid Test—bridging the gap between diagnosis and treatment: performance evaluation study. BMJ 2007;335:1190.

Clinical impact ratings: Family/general practice 5/7; Infectious disease 6/7; Sexual health 6/7; Women’s health 7/7

Commentary

C trachomatis is the most common sexually transmitted bacterial infection in the world, 3 times more common than gonorrhoea.1 If detected, it is easily treatable. Chlamydia infection is commonly seen in adolescent and young adult women. If undiagnosed and untreated, it may result in pelvic inflammatory disease, pregnancy-related complications, and infertility.

The test described in the study by Mahilum-Tapay et al, one that is sensitive and specific and can be rapidly performed in an office setting, is of obvious value in screening women presenting for well-woman care. The ability to retrieve test results rapidly and treat infected women immediately, rather than having women telephone the clinic later, should reduce missed opportunities for detection and treatment of C trachomatis infection. The test would be especially useful in settings where access to nucleic acid-based tests is limited, an immediate test result is required, or return rates are low.

Chlamydia Rapid Test may be of particular importance in developing countries, where rapid case detection and treatment are critical in preventing infertility and promoting healthy pregnancy outcomes. In the past, both Chlamydia and gonorrhoea, frequent coinfections, have been diagnosed in non-western settings based on a “syndromic” approach, which uses a scoring system for specific genitourinary signs and symptoms.2 A recent controlled study in an antenatal clinic in Botswana, where Chlamydia rates are high, found this approach to be neither sensitive nor specific.2 The introduction of a rapid, sensitive, and specific test is crucial to women’s health and wellbeing, especially in parts of the world where sexually transmitted diseases are rampant and a woman’s future often depends on her ability to reproduce.

References

View Abstract

Footnotes

  • Source of funding: Wellcome Trust and NIHR Cambridge Biomedical Research Centre.

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