NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

Nelson HD, Zakher B, Cantor A, et al. Screening for Gonorrhea and Chlamydia: Systematic Review to Update the U.S. Preventive Services Task Force Recommendations [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2014 Sep. (Evidence Syntheses, No. 115.)

Cover of Screening for Gonorrhea and Chlamydia: Systematic Review to Update the U.S. Preventive Services Task Force Recommendations

Screening for Gonorrhea and Chlamydia: Systematic Review to Update the U.S. Preventive Services Task Force Recommendations [Internet].

Show details

4DISCUSSION

Summary of Review Findings

The USPSTF and other groups currently recommend routine screening for gonorrhea and chlamydia in asymptomatic, sexually active women at increased risk for infection because of age or other risk factors, which is the standard of practice in the United States.1,2,13,14,42-46 Previous recommendations were based on various levels of evidence indicating that screening provides an opportunity for earlier identification and treatment of infections and reduces adverse health outcomes and transmission.

A summary of evidence for this update is provided in Table 9. Only one new trial of the effectiveness of screening for chlamydia in nonpregnant women,26 one study of a risk prediction instrument,29 and 10 studies of the diagnostic accuracy of screening tests met inclusion criteria.31-35,37-40 No studies were available to address several Key Questions. These include the effectiveness of screening for gonorrhea in all population groups and for chlamydia in men, pregnant women, and adolescents; the effectiveness of different screening strategies for identifying persons at increased risk for infection, cotesting for concurrent STIs, and different screening intervals; and harms of screening unrelated to the diagnostic accuracy of tests.

Table 9. Summary of Evidence.

Table 9

Summary of Evidence.

Only one new trial evaluated the effectiveness of screening for chlamydia in nonpregnant women26 (Key Question 1). In the POPI trial, screening for chlamydia in a subset of asymptomatic young women did not statistically significantly reduce PID over the following year compared with not screening (RR, 0.39 [95% CI, 0.14 to 1.08]). Although it met criteria for good quality, the POPI trial was limited by inadequate recruitment, testing for chlamydia outside of the study protocol during followup in nearly a quarter of participants, and difficulty in ascertaining PID cases. These limitations imply that the study may have been underpowered and the intervention effects attenuated. In addition, most cases of PID occurred in women who tested negative at baseline, suggesting that frequent targeted screening in women at higher risk for infection, including those with new sex partners or recent history of chlamydia, might be more important than one-time routine screening.

Two earlier trials also evaluated incident PID after screening for chlamydia in women at increased risk.27,28 While a good-quality trial in the United States reported a statistically significant reduction in PID in the screened versus usual care group after 1 year of followup (RR, 0.44 [95% CI, 0.20 to 0.90]),27,28 reduction in PID was not statistically significant in a poor-quality trial in Denmark comparing one-time, home-based screening with usual care.27,28 Although all three trials reported point estimates suggesting reduced PID, only the U.S. trial showed a statistically significant reduction. However, this trial met criteria for good quality, was the largest trial, and was the most applicable to clinical practice in the United States.

Additional relevant studies of screening did not meet inclusion criteria because they did not provide results for asymptomatic participants or reported infection rates rather than health outcomes. These studies found no significant improvements in clinical outcomes among those screened for chlamydia, including a large Danish trial of more than 30,000 young men and women,47 a retrospective population-based cohort study of more than 40,000 Swedish women,48 and a register-based screening trial of more than 300,000 men and women in the Netherlands.49 A time-trend analysis of a U.S. managed care population between 1997 and 2007 indicated an increase in the number of cases of chlamydia in both men and women, but a decrease in PID.50 It is not clear how screening influenced these outcomes.

The only new study addressing the effectiveness of different screening strategies (Key Question 2) was an observational study evaluating a risk prediction tool to identify persons with chlamydia in high-risk populations.29 However, it was not an accurate predictor and its relevance to current practice in the United States is uncertain. An older observational study comparing nine sets of selective screening criteria for chlamydial infection among women30 supports age-based screening in current guidelines, but has not been updated by newer research. Future studies to address this Key Question should compare the effectiveness of screening versus not screening in populations with different levels of risk; use specimens from different anatomical sites; include cotesting for concurrent STIs, including HIV; and evaluate different screening intervals.

Ten studies of the diagnostic accuracy of screening tests met inclusion criteria (Key Question 3).31-35,37-40,51 The current review differs from prior reviews3,4 by including only results from asymptomatic participants, which is more clinically relevant to screening populations. Various types of NAATs are highly accurate in diagnosing gonorrhea and chlamydia in asymptomatic persons regardless of specimen, anatomical site, or test.31-34,37,39,51 Sensitivity was 85 percent or greater and specificity was 97 percent or greater in studies without major methodological limitations, resulting in generally low rates of false-negative and false-positive results. The high accuracy of NAATs reported in these studies is consistent with prior reviews3,4 and is the basis for the CDC's recommendation on using NAATs for gonorrhea and chlamydia screening.10

Several studies of harms (Key Question 4) did not meet inclusion criteria for the update because they focused on the effects of receiving a positive test result, included symptomatic participants, and lacked comparison groups.52-55 In these studies, persons who tested positive for chlamydia had higher measures of anxiety52,53,55 and more partner break-ups52,53 than those who tested negative, who were generally relieved.53,55

No studies addressing screening in pregnant women met inclusion criteria, despite the need for additional research in this population. For example, screening in the first trimester may not be sufficient based on findings from an observational study suggesting that chlamydia test results in the first trimester may not predict chlamydia status during the third trimester.56 Although studies of repeat testing have been conducted in high-risk populations,57 more research is warranted to further evaluate the value of repeat testing during pregnancy to reduce potential complications, such as preterm delivery and premature rupture of membranes.58

Limitations of this review include using only English-language articles, which could result in language bias, though we did not identify non-English–language studies otherwise meeting inclusion criteria in our searches. We only included studies with asymptomatic participants and settings and tests applicable to current practice in the United States to improve clinical relevance for the USPSTF, which excluded much research in the field. Studies were lacking for most Key Questions, and the number, quality, and applicability of studies varied widely. Available screening trials evaluated only PID as the main outcome, while other outcomes are also important.

NAATs are cleared by the FDA for use on male and female urine, endocervical, and male urethral specimens, and some types of NAATs are cleared for use on clinician- and self-collected vaginal specimens in clinical settings. Studies have also reported comparable test characteristics for nurse- and patient-collected rectal swabs in MSM.35,37, 38,40,59 Additional studies of NAATs using self-collected specimens could provide more evidence for FDA clearance of this technique and increase testing access and acceptability, potentially expanding screening strategies to home-, mail-, or Internet-based screening and encouraging uptake of screening among persons at increased risk.

Limiting our review to FDA-cleared tests excluded studies of rectal and pharyngeal specimens that also demonstrated high accuracy with NAATs,35,37,38,40,59 which are currently recommended by the CDC.10 Expanding the range of specimen types for screening has the potential to increase identification of infected persons, especially asymptomatic MSM, in whom nearly 90 percent of all gonococcal infections are at nongenital sites.60 In this population, NAATs have higher sensitivity at extragenital sites compared with culture, possibly because of lower bacterial loads at the pharynx and rectum.61,62 In a study of MSM, 85 percent of rectal infections were asymptomatic and only detectable with routine screening.63 Urethral testing alone missed 84 percent of chlamydial and gonococcal infections compared with 9.8 percent missed by rectal and pharyngeal testing in another study.60

In summary, screening for chlamydia may reduce the incidence of PID in young women. Risk prediction tools may be useful in identifying persons with infections, but require validation in the populations of intended use. NAATs are accurate for diagnosing gonorrhea and chlamydia in asymptomatic persons regardless of specimen, anatomical site, or test. Further research is needed to determine the effectiveness of screening in multiple populations and on various clinical outcomes, including but not limited to PID, effective screening strategies, and harms of screening.

Limitations

The review included only English-language articles published since prior USPSTF reviews and does not reflect the total body of evidence on screening for gonorrhea and chlamydia, although relevant earlier studies were referenced. Studies were lacking for most Key Questions, and the number, quality, and applicability of studies varied widely.

This review explicitly focused on asymptomatic populations and included settings and tests applicable to current practice in the United States. While this approach improves its relevance to the USPSTF, it excludes much research in the field. For example, limiting the review to only FDA-cleared tests excluded studies of rectal and throat specimens that also demonstrated high accuracy with NAATs35,37,38,40,59 and are currently used in practice. This is especially important for screening in asymptomatic MSM, in whom nearly 90 percent of all gonococcal infections are at nongenital sites (throat and rectum).60

Emerging Issues and Next Steps

Screening tests for gonorrhea and chlamydia accurately detect infections. In particular, the sensitivity of NAATs has surpassed culture, the former gold standard. NAATs have been cleared by the FDA for use on male and female urine, endocervical, and male urethral specimens, and some types of NAATs are cleared for use on clinician- and self-collected (in clinical settings) vaginal specimens. Studies have also reported comparable test characteristics for nurse- and patient-collected rectal swabs in MSM.35,37,38,40,59 Additional studies of NAATs using self-collected specimens at various anatomical sites could provide more evidence for FDA clearance of this technique and increase testing access and acceptability. This would expand screening strategies to home-, mail-, or Internet-based screening, and encourage uptake of screening among younger persons at increased risk.

Relevance for Priority Populations

Expanding the range of specimen types for gonorrhea and chlamydia screening has the potential to increase identification of infected persons, particularly among priority populations. For example, the ability to test rectal and pharyngeal specimens may increase detection among MSM. Currently, NAATs are not FDA-cleared for use on rectal or pharyngeal sites in testing for gonorrhea and chlamydia. However, NAATs have improved sensitivity for detecting gonococcal infection at extragenital sites compared with culture in MSM, possibly because of lower bacterial loads at the pharynx and rectum.61,62 Similar findings have been reported for chlamydia testing.61 The prevalence of gonococcal and chlamydial infections varied by anatomical site in a study of MSM, which reported 53 percent of chlamydial and 64 percent of gonococcal infections occurring at rectal and pharyngeal sites, respectively.63 In addition, 85 percent of rectal infections were asymptomatic and would only have been detected with routine screening. In another study of asymptomatic MSM, 84 percent of chlamydial and gonococcal infections were missed by testing for urethral infections only versus 9.8 percent of infections missed by screening only at the rectum and the pharynx.60

Future Research

Research is lacking on the effectiveness of screening for gonorrhea in all population groups and for chlamydia in men, pregnant women, and women without risk factors. Studies evaluating the effectiveness of different screening strategies for identifying persons at increased risk for infection, cotesting for concurrent STIs, and different screening intervals are needed to inform practice guidelines. For example, while no studies addressing repeat testing during pregnancy met inclusion criteria, an observational study conducted in the United States suggested that chlamydia test results in the first trimester may not predict chlamydia status during the third trimester.56 Although studies of repeat testing have been conducted in some high-risk populations,57 more research is warranted to further evaluate the value of repeat testing during pregnancy to reduce potential complications, such as preterm delivery and premature rupture of membranes.58

No studies provided data about potential adverse effects of screening other than those related to test performance for any of the asymptomatic population groups. An observational study of symptomatic and asymptomatic men and women who submitted self-collected specimens (from home) for chlamydia testing reported decreased anxiety after testing, although anxiety for women declined only after receiving negative results.55 Waiting for test results generated anxiety and testing positive was associated with shock and distress for some participants, but many were glad that they had been tested. Additional studies on the harms of screening are needed.

Conclusions

Only one new trial of the effectiveness of screening for chlamydia in women,26 one study of a risk prediction instrument,29 and 10 studies of the diagnostic accuracy of screening tests met inclusion criteria. No studies addressed the effectiveness of screening for gonorrhea in all population groups and for chlamydia in men, pregnant women, and women without risk factors, or the effectiveness of different screening strategies. Aside from false-positive and false-negative findings, no studies provided data about other potential adverse effects of screening for any of the population groups. The findings of the POPI trial suggest benefits of screening for chlamydia for PID prevention, although results were not statistically significant. Screening with NAATs is accurate for diagnosing gonorrhea and chlamydia in asymptomatic persons regardless of specimen, anatomical site, or test. Further research is needed to understand the impact of screening for chlamydia and gonorrhea on clinical outcomes, effective screening strategies, and harms of screening.

Views

  • PubReader
  • Print View
  • Cite this Page
  • PDF version of this title (1.3M)

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...