GC/Chlamydia sampling guidelines per MMWR

new guidelines just came out from the CDC on screening for chlamydia and gonorrhea, with a few significant changes (see http://www.cdc.gov/mmwr/preview/mmwrhtml/rr6302a1.htm?s_cid=rr6302a1_x ). although there is no clear gold standard test for either Chlamydia or gonorrhea, nucleic acid amplification tests (NAATs) are considered the most reliable.  Recommendations:

--Sexually active women less than 26yo as well as those older with risk factors (e.g., new sex partner, multiple partners) should be screened annually for chlamydial infection

--For gonorrhea, there is wide difference in local epidemiology, and testing strategies should be adaptable.  In general targeted screening is indicated in women at high risk, since infections are so frequently asymptomatic.

--For screening in women, the vaginal swab is the preferred specimen type.  These are as sensitive as cervical swabs and there is no difference in specificity.  Self-collected vaginal swabs are of equal sensitivity and specificity.  Cervical swabs are acceptable, though vaginal swabs are considered to be the appropriate sample type, even when full pelvic exams are being done (no data presented as to why vaginal swabs preferred....).  First catch urines, “while acceptable for screening, might detect up to 10% fewer infections when compared with vaginal and endocervical swab samples".

--For men, the consensus on testing is less clear.  The USPSTF suggest testing sexually active heterosexual man in clinical settings with a high prevalence of Chlamydia.  For gonorrhea, again, the prevalence varies in different communities.  It is not appropriate to check men at low risk for infection.  And in general for men first catch urine samples are highly acceptable for both gonorrhea and chlamydia, and probably better than urethral swabs. 

--For men and women with a positive NAAT for gonorrhea, treatment should be offered.  A repeat NAAT should be done at least 7 days after treatment, and if positive, a swab specimen should be sent for culture (endocervical for women and urethral for men), assuming that the person did not engage in sexual activity in this interim period.

--NAATs are the preferred test for rectal and oropharyngeal specimens as well (though not cleared for this indication by the FDA).  There may be some false positives in the oropharyngeal specimens, since other,commensal neisseria species may be present.  Again, if positive, and a repeat NAAT is positive more than 7 days after treatment, a culture should be sent for antibiotic susceptibility.

so, this brings up a few issues. the Massachusetts State Lab has taken the strong position that any testing is better than no testing: so, a streamlined system where medical assistants regularly get urines for routine chlam/gonorrhea screening is superior to one which gets the slightly better test of vaginal swabs but is less consistent in getting specimens. also, for the assays we use (Becton-Dickenson at the state lab, Aptima at boston medical center), you need a special vaginal swab kit for the vaginal secretion collection (ie, though counterintuitive, you cannot use the endocervical swab to collect the vaginal sample). boston medical center can provide these special swab kits, to be used in facilities where either the clinician does the sampling or the patients have "procedural supervision" and support to explain how the woman collects their own samples, and the women are not pregnant and at least 16 years old. so, bottom line: vaginal swabs are better for detection of chlamydia in women, but should only be implemented if there are systems to support this process, and a change to vaginal swabs does NOT lead to decreased screening.