U.S. Preventive Services Task Force

Screening for Chlamydial Infection: Recommendation Statement



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This statement summarizes the U.S. Preventive Services Task Force (USPSTF) recommendations on screening for chlamydial infection and the supporting scientific evidence. See Table 1 for a description of the USPSTF grades and Table 2 for a description of USPSTF classification of levels of certainty regarding net benefit. The complete information on which this statement is based, including evidence tables and references, is included in the evidence synthesis1 and brief evidence update2 on this topic, available on the USPSTF Web site at: http://www.uspreventiveservicestaskforce.org. The recommendation is also posted on the Web site of the National Guideline Clearinghouse at http://www.guideline.gov.

Summary of Recommendations and Evidence

The USPSTF recommends screening for chlamydial infection in all sexually active, nonpregnant women 24 years or younger and in older nonpregnant women who are at increased risk. A recommendation.

The USPSTF recommends screening for chlamydial infection in all pregnant women 24 years or younger and in older pregnant women who are at increased risk. B recommendation.

The USPSTF recommends against routinely providing screening for chlamydial infection in women 25 years or older, whether or not they are pregnant, if they are not at increased risk. C recommendation.

The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for chlamydial infection in men. I statement. (See Assessment of Risk and Suggestions for Practice with Regard to Insufficient Evidence in the Clinical Considerations section below for discussions on assessing risk for chlamydial infection in women and suggestions for practice regarding screening for men.)

Rationale

Importance. Chlamydial infection is the most common sexually transmitted bacterial infection in the United States. In women, genital chlamydial infection may result in urethritis, cervicitis, pelvic inflammatory disease, infertility, ectopic pregnancy, and chronic pelvic pain. Chlamydial infection during pregnancy is related to adverse pregnancy outcomes, including miscarriage, premature rupture of membranes, preterm labor, low birth weight, and infant mortality.

Detection. The USPSTF found fair evidence that nucleic acid amplification tests can identify chlamydial infection in asymptomatic men and women, including asymptomatic pregnant women, with high test specificity. In populations with low infection prevalence, however, a positive test is more likely to be a false positive than a true positive, even with the most accurate tests available.

Benefits of Detection and Early Intervention. There is good evidence that screening for chlamydial infection in nonpregnant women who are at increased risk can reduce the incidence of pelvic inflammatory disease. The USPSTF concluded that the benefits of screening women at increased risk are substantial.

There are no studies evaluating the effectiveness of screening for chlamydial infection in pregnant women who are at increased risk. The USPSTF, however, found the following: (1) screening identifies infection in asymptomatic pregnant women; (2) there is a relatively high prevalence of infection among pregnant women who are at increased risk; and (3) there is fair evidence of improved pregnancy and birth outcomes for women who are treated for chlamydial infection. The USPSTF concluded that the benefits of screening pregnant women who are at increased risk are substantial.

Table 1

What the USPSTF Grades Mean and Suggestions for Practice

Grade Grade definition Suggestions for practice

A

The USPSTF recommends the service. There is high certainty that the net benefit is substantial

Offer/provide this service

B

The USPSTF recommends the service. There is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial

Offer/provide this service

C

The USPSTF recommends against routinely providing the service. There may be considerations that support providing the service in an individual patient. There is moderate or high certainty that the net benefit is small

Offer/provide this service only if there are other considerations in support of offering/providing the service in an individual patient

D

The USPSTF recommends against the service. There is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits

Discourage the use of this service

I

The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the service. Evidence is lacking, of poor quality or conflicting, and the balance of benefits and harms cannot be determined

Read “Clinical Considerations” section of USPSTF Recommendation Statement. If this service offered, patients should understand the uncertainty about the balance of benefits and harms


USPSTF = U.S. Preventive Services Task Force.

Table 1   What the USPSTF Grades Mean and Suggestions for Practice

View Table

Table 1

What the USPSTF Grades Mean and Suggestions for Practice

Grade Grade definition Suggestions for practice

A

The USPSTF recommends the service. There is high certainty that the net benefit is substantial

Offer/provide this service

B

The USPSTF recommends the service. There is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial

Offer/provide this service

C

The USPSTF recommends against routinely providing the service. There may be considerations that support providing the service in an individual patient. There is moderate or high certainty that the net benefit is small

Offer/provide this service only if there are other considerations in support of offering/providing the service in an individual patient

D

The USPSTF recommends against the service. There is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits

Discourage the use of this service

I

The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the service. Evidence is lacking, of poor quality or conflicting, and the balance of benefits and harms cannot be determined

Read “Clinical Considerations” section of USPSTF Recommendation Statement. If this service offered, patients should understand the uncertainty about the balance of benefits and harms


USPSTF = U.S. Preventive Services Task Force.

The USPSTF identified no studies documenting the benefits of screening women, including pregnant women, who are not at increased risk for chlamydial infection. While recognizing the potential benefit to women identified through screening, the USPSTF concluded that the overall benefit of screening would be small, given the low prevalence of infection among women not at increased risk.

While concluding that the direct benefit to men of screening was likely to be small, the USPSTF noted that screening for chlamydial infection in men may be beneficial if it were to lead to a decreased incidence of chlamydial infection in women. The USPSTF did not, however, find evidence to support this outcome, and therefore concluded that the benefits of screening men are unknown. The USPSTF identified this as a critical gap in the evidence.

Harms of Detection and Early Treatment. The USPSTF concluded that the harms of screening for chlamydial infection are no greater than small, although few studies have been published on this subject. Potential harms include anxiety and relationship problems arising from false-positive results and overtreatment. The USPSTF identified the lack of evidence related to potential harms of screening as a gap in the evidence.

The USPSTF reached the following conclusions:

In nonpregnant women at increased risk, the certainty is high that the benefits of screening for chlamydial infection substantially outweigh the harms. A recommendation.

In pregnant women at increased risk, the certainty is moderate that the benefits substantially outweigh the harms of screening for chlamydial infection. B recommendation.

In women not at increased risk (including pregnant women not at increased risk), the certainty is moderate that the benefits outweigh the harms of screening to only a small degree. There may be considerations that support screening an individual patient. C recommendation.

In men, the benefits of screening are not known; thus, the USPSTF could not determine the balance of benefits and harms of screening men for chlamydial infection. I statement.

Clinical Considerations

  • Patient Population Under Consideration. These recommendations target all sexually active persons, including adolescents and pregnant women.

  • Assessment of Risk. All sexually active women 24 years or younger, including adolescents, are at increased risk for chlamydial infection. In addition to sexual activity and age, other risk factors for chlamydial infection include a history of previous chlamydial or other sexually transmitted infection, new or multiple sex partners, inconsistent condom use, and exchanging sex for money or drugs. Risk factors for pregnant women are the same as those for nonpregnant women. Prevalence of chlamydial infection varies widely among patient populations. Black and Hispanic women have a higher prevalence of infection than the general population in many communities and settings. Among men and women, increased prevalence rates are also found in incarcerated populations, military recruits, and patients at public sexually transmitted infection clinics.

  • Screening Tests. Nucleic acid amplification tests have high specificity and sensitivity when used as screening tests for chlamydial infection. They can be used with urine and vaginal swabs, enabling screening when a pelvic examination is not performed.

  • Treatment. Appropriate treatment of chlamydial infection has been outlined by the Centers for Disease Control and Prevention (CDC) and can be found at http://www.cdc.gov/std/treatment/. In its 2006 sexually transmitted disease treatment guidelines, the CDC recommends that chlamydial infection be treated with 1 g of azithromycin (Zithromax) in a single oral dose or with oral doxycline (Vibramycin) at a dosage of 100 mg twice daily for seven days. Pregnant women with chlamydial infection may be treated with 1 g of azithromycin in a single dose or with oral amoxicillin at a dosage of 500 mg three times daily for seven days.3 Because the CDC updates these recommendations regularly, physicians are encouraged to access the CDC Web site to obtain the most up-to-date information. To prevent recurrent transmission, physicians should ensure that all sex partners of infected persons are tested and treated, if infected, or treated presumptively.

  • Screening Intervals. Screening for pregnant women who are at increased risk for chlamydial infection is recommended at the first prenatal visit. In pregnant women who remain at increased risk, and in those who acquire a new risk factor, such as a new sex partner, screening should be conducted during the third trimester. The optimal interval for screening in nonpregnant women is unknown. The CDC recommends at least annual screening in women at increased risk.3

Table 2

USPSTF Levels of Certainty Regarding Net Benefit

Level of certainty Description

High

The available evidence usually includes consistent results from well-designed, well-conducted studies in representative primary care populations. These studies assess the effects of the preventive service on health outcomes. This conclusion is therefore unlikely to be strongly affected by the results of future studies

Moderate

The available evidence is sufficient to determine the effects of the preventive service on health outcomes, but confidence in the estimate is constrained by factors such as:

  • the number, size, or quality of individual studies

  • inconsistency of findings across individual studies

  • limited generalizability of findings to routine primary care practice

  • lack of coherence in the chain of evidence

As more information becomes available, the magnitude or direction of the observed effect could change, and this change may be large enough to alter the conclusion

Low

The available evidence is insufficient to assess effects on health outcomes. Evidence is insufficient because of:

  • the limited number or size of studies

  • important flaws in study design or methods

  • inconsistency of findings across individual studies

  • gaps in the chain of evidence

  • findings not generalizable to routine primary care practice

  • a lack of information on important health outcomes

More information may allow an estimation of effects on health outcomes


note: The USPSTF defines certainty as “likelihood that the USPSTF assessment of the net benefit of a preventive service is correct.” The net benefit is defined as benefit minus harm of the preventive service as implemented in a general, primary care population. The USPSTF assigns a certainty level based on the nature of the overall evidence available to assess the net benefit of a preventive service.

USPSTF = U.S. Preventive Services Task Force.

Table 2   USPSTF Levels of Certainty Regarding Net Benefit

View Table

Table 2

USPSTF Levels of Certainty Regarding Net Benefit

Level of certainty Description

High

The available evidence usually includes consistent results from well-designed, well-conducted studies in representative primary care populations. These studies assess the effects of the preventive service on health outcomes. This conclusion is therefore unlikely to be strongly affected by the results of future studies

Moderate

The available evidence is sufficient to determine the effects of the preventive service on health outcomes, but confidence in the estimate is constrained by factors such as:

  • the number, size, or quality of individual studies

  • inconsistency of findings across individual studies

  • limited generalizability of findings to routine primary care practice

  • lack of coherence in the chain of evidence

As more information becomes available, the magnitude or direction of the observed effect could change, and this change may be large enough to alter the conclusion

Low

The available evidence is insufficient to assess effects on health outcomes. Evidence is insufficient because of:

  • the limited number or size of studies

  • important flaws in study design or methods

  • inconsistency of findings across individual studies

  • gaps in the chain of evidence

  • findings not generalizable to routine primary care practice

  • a lack of information on important health outcomes

More information may allow an estimation of effects on health outcomes


note: The USPSTF defines certainty as “likelihood that the USPSTF assessment of the net benefit of a preventive service is correct.” The net benefit is defined as benefit minus harm of the preventive service as implemented in a general, primary care population. The USPSTF assigns a certainty level based on the nature of the overall evidence available to assess the net benefit of a preventive service.

USPSTF = U.S. Preventive Services Task Force.

  • Suggestions for Practice with Regard to Insufficient Evidence on Screening in Men. The USPSTF concluded that the evidence is insufficient to determine the balance of benefits and harms related to screening men for chlamydial infection. Specifically, the USPSTF did not find evidence that screening programs that target men result in a decreased incidence of infection in women. The USPSTF notes that programs that screen men as a means of reducing transmission to women are not common practice; that primary care physicians are capable of instituting screening in men; that the costs of additional screening tests per person are relatively low; and that the potential harms of screening are small. The USPSTF recognizes that asymptomatic, untreated infections in men provide a reservoir of infection that may make it difficult to improve health outcomes in women through screening programs that target only women. However, given the low national rates of screening in women at risk, the USPSTF believes that physicians and health care systems should focus on improving screening rates among women at increased risk, a group in which the benefits of screening are certain.

  • Other Approaches to Prevention. Primary care physicians and the health care systems in which they work are responsible for ensuring that asymptomatic women at risk for chlamydial infection are screened. In some communities, this may involve home-or school-based screening programs.

  • Useful Resources. See other USPSTF recommendations on screening for sexually transmitted infections (i.e., hepatitis B and C, human immunodeficiency virus, genital herpes simplex, gonorrhea, and syphilis) at http://preventiveservices.ahrq.gov.

Other Considerations

  • Health Care System Needs. U.S. screening rates for chlamydial infection among young women remain very low. Public health organizations, health care systems, and physicians must work together to develop and implement effective programs to ensure that all women at increased risk are screened for chlamydial infection.

  • Research Needs. There is currently a critical gap in the evidence relating to whether chlamydia screening programs that target men decrease the incidence of infection among women. Additional research is also needed to determine the most effective intervals for screening nonpregnant women, including the potential for different follow-up intervals for women with positive or negative test results. Continued research is also needed on the potential harms of screening.

The Discussion and Recommendations from Others sections and the list of USPSTF members at the time this recommendation was finalized are available in the full recommendation statement on the USPSTF Web site at http://www.ahrq.gov/clinic/uspstf07/chlamydia/chlamydiars.htm.

This recommendation statement was first published in Ann Intern Med 2007;147:128–34.

The U.S. Preventive Services Task Force recommendations are independent of the U.S. government. They do not represent the views of the Agency for Healthcare Research and Quality, the U.S. Department of Health and Human Services, or the U.S. Public Health Service.

 

REFERENCES

1. Meyers D, Halvorson H, Luckhaupt S. Screening for chlamydial infection: a focused evidence update for the U.S. Preventive Services Task Force. Evidence synthesis no. 48. Rockville, Md.: Agency for Healthcare Research and Quality. Accessed September 10, 2007, at: http://www.ahrq.gov/clinic/uspstf07/chlamydia/chlamydiasyn.pdf.

2. Meyers DS, Halvorson H, Luckhaupt S. Screening for chlamydial infection: an evidence update. Accessed September 10, 2007, at: http://www.ahrq.gov/clinic/uspstf07/chlamydia/chlamydiaup.htm.

3. Centers for Disease Control and Prevention, Workowski KA, Berman SM. Sexually transmitted diseases treatment guidelines, 2006 [published correction appears in MMWR Recomm Rep 2006;55:997]. MMWR Recomm Rep. 2006;55(RR-11):1–94.

This summary is one in a series excerpted from the Recommendation Statements released by the U.S. Preventive Services Task Force (USPSTF). These statements address preventive health services for use in primary care clinical settings, including screening tests, counseling, and preventive medications. The practice recommendations in this activity are available at http://www.ahrq.gov/clinic/uspstf07/chlamydia/chlamydiars.htm.

The series coordinator for AFP is Charles Carter, MD, Palmetto Health Family Medicine Residency Program/University of South Carolina School of Medicine, Columbia, S.C.



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