Putting Prevention into Practice: An Evidence-Based Approach

Screening for Chlamydial Infection

Am Fam Physician. 2002 Jul 1;66(1):139-140.

Case Study

TC is a 24-year-old woman who comes to your office for a well-woman visit. Her last physical examination was at age 16 with her pediatrician. She has been sexually active since the age of 15 and has had three “lifetime” partners. TC has been monogamous with her current partner since they were married four months ago. She is currently taking oral contraceptive pills and has used condoms inconsistently in the past. TC has had two miscarriages and also has a family history of breast cancer. She has never been tested for sexually transmitted infections and asks if this is necessary.

Case Study Question

1. Which one of the following statements regarding recommendations accepted by the U.S. Preventive Services Task Force (USPSTF) for chlamydial infection screening is correct?

  • A. The USPSTF strongly recommends routine screening for chlamydial infection in all sexually active women 25 years of age and younger.

  • B. The USPSTF strongly recommends chlamydial screening for all pregnant women, regardless of risk factors.

  • C. The optimal timing of chlamydial screening in pregnancy is during the second trimester.

  • D. The USPSTF does not recommend the routine screening of high-risk young men.

2. Which one of the following is the most important risk factor for chlamydial infection?

  • A. Having new or multiple sexual partners.

  • B. History of miscarriages.

  • C. Inconsistent use of barrier contraceptives.

  • D. Age younger than 25 years.

Answers

1. The answer is A: The USPSTF found good evidence that screening women at risk for chlamydial infection reduces the incidence of pelvic inflammatory disease and fair evidence that community-based screening reduces the prevalence of chlamydial infection. A number of tests that use endocervical or urethral swab specimens and urine specimens are available to identify chlamydial infection. Until recently, culture has been accepted as the most specific test, but it requires specialized handling and laboratory services. Antigen detection tests and nonamplified nucleic acid hybridization, as well as newer technologies based on amplified DNA assays, may provide improved sensitivity, increased availability, faster turnaround time, and reduced cost as compared with culture. New urine-based tests provide a noninvasive method of screening men and women.

The optimal interval for screening is uncertain. For women with a previous negative screening test, the interval should take into account changes in sexual partners. Rescreening at six to 12 months may be appropriate for previously infected women because of the high incidence of reinfection.

Fair evidence exists to indicate that screening for and treating chlamydial infection in asymptomatic, high-risk, pregnant women improve pregnancy outcomes. Two nonrandomized trials demonstrated improved pregnancy outcomes following treatment of chlamydial infection, including lower incidences of premature rupture of the membranes, low birth weight, and small-for-gestational-age births, and higher rates of infant survival. Little evidence is available regarding the effectiveness of screening and treatment of asymptomatic pregnant women who are not at high risk. The incremental benefit of repeated screening is unknown.

The optimal time for screening during pregnancy is uncertain. Screening early in pregnancy provides greater opportunities to improve pregnancy outcomes, including low birth weight and preterm delivery; however, screening in the third trimester may allow for more effective prevention of transmission of chlamydial infection to the infant during birth.

Screening of high-risk young men is a clinical option. Before the advent of urine-based screening tests, routine screening was rarely performed in men. Trials are under way, but currently little evidence exists regarding whether screening in asymptomatic men can help reduce infection rates in men and their partners. Partners of infected persons should be tested and treated if infected, or treated presumptively.

2. The answer is D: Age is the most important risk factor for chlamydial infection. Women and adolescents through 20 years of age are at highest risk for chlamydial infection, but most reported data indicate that infection is prevalent among women 20 to 25 years of age. Other patient characteristics associated with a higher prevalence of infection include being unmarried, African-American race, history of sexually transmitted infection, new or multiple sexual partners, cervical ectopy, and inconsistent use of barrier contraceptives.

Knowledge of the patient population is the best guide to developing a reasonable screening strategy. Clinicians should consider the profile of the communities they serve as they plan appropriate screening strategies for their patient population.

The case study and answers to the following questions on screening for chlamydia are based on the recommendations of the current U.S. Preventive Services Task Force (USPSTF), part of the Put Prevention into Practice program of the Agency for Healthcare Research and Quality (AHRQ). This recommendation was released in 2001 and is an update of the 1995 USPSTF Recommendations and Rationale Statement on screening for chlamydial infection. More detailed information on this subject is available in the Systematic Evidence Review, Summary of the Evidence, and USPSTF Recommendations and Rationale on the AHRQ Web site ( www.ahrq.gov); through the National Guideline Clearinghouse ( www.guideline.gov); and in print through the AHRQ Publications Clearinghouse (800-358-9295) and the April 2001 Supplement to the American Journal of Preventive Medicine.

This case study is part of AFP's CME. See “Clinical Quiz” on page 21.


Copyright © 2002 by the American Academy of Family Physicians.
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