Self-Taken Vaginal Swab Tested by Nucleic Acid Amplification Detects More Chlamydia Infections Than Clinician-Obtained Endocervical Swab
EBM Focus - Volume 8, Issue 1
Chlamydia is one of the most common sexually transmitted infections in women. Diagnostic samples may be obtained by clinicians during a pelvic examination, by urine sample, or by vaginal swabs taken by the patient. The optimal sampling method is unclear. A recent cohort study compared the diagnostic performance of self-taken vaginal swabs and clinician-obtained endocervical swabs for detection of C. trachomatis infection.
A total of 3,976 women ≥ 16 years old (35% asymptomatic) who were requesting testing for sexually transmitted infections took a self vulvovaginal swab prior to clinical examination. During examination, the clinician obtained an endocervical swab. Both swabs were tested using a nucleic acid amplification test (NAAT) designed to detect both chlamydia and gonorrhea. Any swab with a positive result of the first test was confirmed with a second NAAT specific for chlamydia. Chlamydia was diagnosed if either swab resulted in 2 positive test results.
C. trachomatis infection was detected in 10.3% of women. The detection rates were 97% for the self-taken vaginal swab and 88% for the clinician-obtained endocervical swab (p < 0.0001) (level 1 [likely reliable] evidence). Subgroup analyses of both symptomatic women and asymptomatic women showed nearly identical results to the overall analysis (BMJ 2012 Dec 12;345:e8013).
In a companion publication using the same samples and methodology, the two sampling approaches were compared for the detection of gonorrhea infections. Detection rates were 99% for self-taken vaginal swabs and 96% for endocervical swabs in overall analysis (not significant). In asymptomatic women, vaginal swabs had a 98% detection rate compared to 90% for the endocervical swabs (BMJ 2012 Dec 12;345:e8107).