NEW YORK (Reuters Health) – While first-void urine specimens have been used traditionally to test for Chlamydia trachomatis, newer DNA detection methods produce reliable results using midstream specimens, a New Zealand group reports in the January/February issue of the Annals of Family Medicine.
“The clinical practice implications of these results are important: urine culture and C trachomatis testing may be considered on a single specimen,” the authors comment, noting that midstream urine specimens are usually recommended in cases of presumed bacterial urinary tract infections.
As the ability to test for both C trachomatis and urinary tract infections in a single midstream specimen would be useful, the team conducted a study to determine how well C trachomatis results on first-void (i.e., urethral) specimens correlated with results using paired midstream (i.e., bladder) specimens.
The prospective study involved sample collection of both first-void and midstream urine specimens from women with a recent vaginal swab that tested positive for C trachomatis, Dr. Derelie Mangin, at Christchurch School of Medicine and Health Sciences, and colleagues explain.
All C trachomatis testing was done with the BD ProbeTec strand displacement amplification system. Among 100 women with a positive first-void specimen, 96 were also positive on the midstream specimen, the report indicates. In other words, the sensitivity of midstream testing was 96%.
“If the results of this pilot study are confirmed in similar studies, NAAT (nucleic acid amplification testing) offers the possibility that midstream urine specimens in women may be sufficiently equivalent to testing first-void specimens in clinical practice as a case finding tool to improve detection of C trachomatis where collecting other types of samples is impracticable,” Dr. Mangin and colleagues conclude.
“It also provides a basis for prevalence estimates in research settings where midstream urine specimens are available,” they add.
SOURCE:
Chlamydia trachomatis Testing Sensitivity in Midstream Compared With First-Void Urine Specimens
Ann Fam Med 2012;10:50-53.
