Question
What are the performances of a latex agglutination test, wet preparation, and culture for the detection of T. vaginalis in pregnant women in Ghana?

Design
Pregnant women in Ghana were tested for T. vaginalis infection by a latex agglutination test, saline wet mount, and culture.  The performance of the assays was determined using a gold standard based on the wet mount and culture results.

Participants
Consecutive pregnant women (n = 3807) attending antenatal clinics in Kumasi, Ghana were tested using the latex agglutination test.  All women positive for T. vaginalis by latex agglutination (n = 206) and the next two women testing negative (n = 412) were tested by wet mount and culture.  Of these 618 women, 55.5% were symptomatic for vaginitis.  

Description of Tests and Diagnostic Standard
Self-administered vaginal swabs were tested for T. vaginalis using the TV latex agglutination test (Kalon Biologicals, Surrey, UK).  The swabs were eluted into saline and one drop was mixed with a drop of latex on a glass slide, which was rocked for 2 minutes.  Agglutination of the test but not the control sample indicated a positive test for T. vaginalis.  Two vaginal swabs collected by a nurse after speculum insertion were tested by wet mount and culture.  One swab was agitated in saline and a drop was observed by microscopy at 100X for motile T. vaginalis.  The second swab was inoculated into a T. vaginalis InPouch bag (Biomed Diagnostics, San Jose, CA) as previously described.  All swabs were tested within 10 minutes of collection.  The culture was incubated at 37^oC within 1 h of inoculation.  All tests were read independently by different technicians who were blinded to the results of the other tests.  Women were considered to have T. vaginalis infection when either the wet mount or culture were positive and considered negative for T. vaginalis infection when both wet mount and culture were negative.  

Main Outcome Measures
The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of latex agglutination, wet mount, and culture for the detection of T. vaginalis as determined by the results of wet mount and culture were determined.   

Main Results
Thirty-five of the 206 latex agglutination positive women were negative by both wet mount and culture.  Four hundred ten of the 412 latex agglutination negative women were negative for both wet mount and culture; one women was positive by wet mount only and one woman was positive by culture only.  The performance of the three tests for the detection of T. vaginalis as determined by the results of wet mount and culture is shown in the table.  The kappa value was 0.93 for agreement between latex agglutination and culture and 0.88 for agreement between latex agglutination and wet prep.   

Performance of latex agglutination, wet mount, and culture for detection of T. vaginalis in 618 pregnant women in Ghana

Authors’ Conclusions
The sensitivity of the latex agglutination test compared favorably with culture and was higher than that of the wet mount test.  The test is simple to perform and more cost effective than culture, requires no equipment, and gives a result in less than 3 minutes, which allows for prompt diagnosis and treatment.    

Source of funding:  None given

For correspondence:  Y. Adu-Sarkadie, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.  E-mail address:  adu-sarkadie@lshtm.ac.uk.