PRACTICE CHANGER
Ask women who are at risk for sexually transmitted infections (STIs) to self-swab for chlamydia and gonorrhea testing; self-collection of vulvovaginal swabs with nucleic acid amplification testing (NAAT) has excellent sensitivity in women with and without symptoms.1,2
STRENGTH OF RECOMMENDATION
B: Based on a prospective diagnostic cohort study.1,2
ILLUSTRATIVE CASE
An 18-year-old patient requests testing for STIs. She has no symptoms. What is the best way to collect samples for chlamydia and gonorrhea testing?
Despite public health efforts, chlamydia and gonorrhea remain significant health problems, with more than 1.4 million cases of chlamydia and 321,849 cases of gonorrhea reported in the United States in 2011.3 Both can have devastating effects on reproduction, even in women who are asymptomatic.
Annual testing recommended for at-risk women
According to the CDC, most reported cases of chlamydia (70%) and gonorrhea (62%) occur in men and women between the ages of 15 and 24.3 Both the CDC and the US Preventive Services Task Force recommend annual chlamydia screening for all sexually active women younger than 25 and for older women who have certain risk factors (eg, having multiple sex partners or living in communities with a high burden of disease).4,5 Annual gonorrhea screening is also recommended for sexually active women with risk factors.4,5
How best to test? A number of unknowns
NAAT is the most sensitive test for detection of chlamydia and gonorrhea, but other questions about how best to screen for STIs remain.1,6 It has not been clear whether self-collected vulvovaginal swabs are equivalent to clinician-collected urethral or endocervical swabs for the detection of gonorrhea, or whether NAAT testing of the self-collected swabs or culture of the clinician-collected swabs is a more sensitive test for gonorrhea.
While some studies have found self-collected vulvovaginal samples to be as sensitive as clinician-collected endocervical samples for the diagnosis of chlamydia and gonorrhea, samples are still often collected by clinicians.7,8 Collecting endocervical swabs is uncomfortable for patients and time consuming for clinicians, and evidence suggests that patients prefer noninvasive sampling.9
STUDY SUMMARY
Self-collected samples are highly sensitive
This study was designed to compare the sensitivity and specificity of self-collected vulvovaginal swabs with that of clinician-collected swabs for chlamydia and gonorrhea, both in asymptomatic women and women with symptoms of an STI. Test methods were also assessed for gonorrhea, comparing detection rates of self-swabs tested with NAAT and the culture of clinician-collected urethral and endocervical samples.
The researchers evaluated a total of 3,973 women, ages 16 to 59, who sought care at a single sexual health center in the United Kingdom. The average age was 25; 37% of the participants reported a prior STI, and 42% had at least one symptom suggestive of an STI. Women were excluded from the study if they had taken an antibiotic in the preceding 28 days or were unable/unwilling to take a vulvovaginal swab or undergo clinician examination and sample collection.
The women performed vulvovaginal swabs for NAAT prior to a speculum exam; endocervical swab for both NAAT and culture and a urethral swab for culture were collected by the clinician. All the swabs sent for NAAT were tested for chlamydia and gonorrhea, and cultures were performed to detect gonorrhea.
Chlamydia: Vulvovaginal swabs have higher detection rates
Of the 3,867 participants with complete results, 10.2% were infected with chlamydia. Self-collected vulvovaginal swabs were significantly more sensitive than endocervical swabs (97% vs 88%) and had equal specificity (99.9% vs 100%). In women with symptoms of an STI, the sensitivity was 97% vs 88%; in those with no symptoms, the sensitivity was 97% vs 89%.
Gonorrhea: Self-collection, NAAT yield better results
Gonorrhea was found in 2.5% of the 3,859 women with complete results for testing of this STI. Self-collected swabs and clinician-collected swabs analyzed by NAAT both had excellent sensitivity (99% and 96%, respectively). But self-collected samples that underwent NAAT were significantly more sensitive than clinician-collected urethral and endocervical samples that were cultured (99% vs 81%). The number needed to test by self-collection for NAAT (compared with clinician-collected culture) to detect one additional case of gonorrhea was 5.
In women with symptoms suggestive of infection, the NAAT assays—both clinician- and self-collected—were equivalent and were more sensitive than gonorrhea culture. In asymptomatic women, 1.8% of whom had gonorrhea, the vulvovaginal swab sent for NAAT was more sensitive than culture (98% vs 78%) and was equivalent to the endocervical swab for NAAT (90%).
The bottom line: Self-collected vulvovaginal swabs are the sample of choice for both chlamydia and gonorrhea testing in women, regardless of whether they have symptoms. When a clinical examination is needed, either the clinician or the patient can collect a vulvovaginal swab.