Midstream samples might be adequate for evaluating both chlamydial and urinary tract infections, but study results were not definitive.

First-void urine samples are recommended for diagnosing chlamydia with nucleic acid amplification tests, whereas midstream specimens are used for sediment evaluation and bacterial culture. Might midstream samples be sufficient for both purposes? In a New Zealand study, women with known chlamydial infections (based on positive vaginal swabs) collected concomitant first-catch and midstream urine samples; researchers then calculated the sensitivity of midstream urine specimen testing for detection of Chlamydia trachomatis.

Of 100 women with positive first-void urine specimens, 96 also had positive midstream specimens. However, 8 women had been excluded because they had positive vaginal swabs and negative (7) or inconclusive (1) first-void urine samples. Including these women in the calculations would lower the estimated sensitivity of midstream urine specimens to just 90%.


Citation(s):

Mangin D et al. Chlamydia trachomatis testing sensitivity in midstream compared with first-void urine specimens. Ann Fam Med 2012 Jan/Feb; 10:50.