Summary and conclusions
Chlamydia is by far the most commonly reported sexually transmitted infection (STI) in Sweden. It is mandatory to report all new cases to the Swedish Institute for Infectious Disease Control and to the county council’s physician in charge of infectious disease control. Chlamydia is transmitted through unprotected sexual contact. Most people infected do not present obvious symptoms. Untreated, chlamydia can lead to permanent lesions and infertility.
In women, chlamydia can be diagnosed by analyzing cervical, vaginal, or urine specimens. Women can collect vaginal and urine specimens themselves.
SBU’s appraisal of the evidence
- Urine specimens are somewhat less sensitive (ie, miss more cases) than vaginal and cervical specimens. Vaginal specimens have the highest sensitivity for diagnosing chlamydia in women.
- Urine, vaginal, and cervical specimens have similar specificity. In other words, they are equally likely to yield a correct, ie, negative, finding in women who are not infected.
- The scientific evidence is insufficient to compare the diagnostic accuracy of urine specimens alone versus various combinations of specimens, since only one study in the assessment included such a comparison.
- The scientific evidence is insufficient to draw conclusions on the cost-effectiveness of using urine specimens as the only test for establishing a chlamydia diagnosis in women. Too few studies of sufficient quality are available. The total cost of chlamydia testing is influenced mainly by how specimens are taken. Vaginal and urine specimens can be collected by the patient herself. This lowers the cost in comparison to taking cervical specimens, where health professionals must collect the specimen.
Technology and target group
Chlamydia often affects young people. In women, untreated chlamydia can lead to pelvic inflammatory disease, which can cause permanent damage to the fallopian tubes and create risks for sterility and ectopic pregnancy. The infection can be transmitted from mother to child through childbirth, leading to eye infection or pneumonia in the child.
In Sweden, chlamydia testing is offered in suspected cases, but sexually active individuals not directly suspected of infection are also offered screening tests when they are in contact with health services (ie, opportunistic screening). In women, chlamydia has been diagnosed primarily by using a combination of specimens from the urethra and cervix, or a combination of urine specimens and cervical specimens. This requires a gynecological examination.
Diagnostic advancements in chlamydia have progressed rapidly in recent years, and it has become increasingly common to use vaginal specimens alone, or urine samples alone. Both of these methods offer the option of self-collection of specimens. This could be a way to increase chlamydia testing, particularly among younger women who might otherwise fail to provide specimens. However, it is uncertain whether urine samples alone yield sufficiently high diagnostic accuracy in diagnosing chlamydia in women.
- What is the diagnostic accuracy of urine samples alone compared to cervical specimens, vaginal specimens, or combinations of specimens in diagnosing chlamydia in women?
- What does it cost to diagnose chlamydia by using urine samples alone? What is the cost-effectiveness of the method?
- Urine specimens yield somewhat lower sensitivity than vaginal and cervical specimens (Evidence grade 3)*.
- Specificity is similar for urine, vaginal, and cervical specimens (Evidence grade 3)*.
- The scientific evidence is insufficient* to compare the diagnostic accuracy of urine specimens versus a combination of specimens.
This assessment included 6 studies, all of which were judged to be of medium quality [14–19]. Populations studied were women with and without symptoms of chlamydia. The studies reported a range of 4.1% to 50% in the prevalence of chlamydia.
The studies compared urine specimens versus cervical or vaginal specimens from the same woman. SDA or PCR1 methods were used to analyze the samples. The reported sensitivity for detecting chlamydia ranged between 85% and 95.5% for urine specimens and between 87% and 97% for cervical specimens. Four of the studies also analyzed the sensitivity of vaginal specimens, which ranged between 95.5% and 97%. One of the studies analyzed the sensitivity of combined urine and vaginal specimens, which was 95%. Specificity was similar (95% or higher) for urine, cervical, and vaginal specimens.
- The scientific evidence is insufficient* to draw conclusions on the cost-effectiveness of using urine specimens alone to diagnose chlamydia in women, since there are too few studies of sufficient quality.
Analysis cost is approximately 200 Swedish kronor (SEK) per test regardless of specimen type. The total cost of chlamydia testing is influenced mainly by the method of specimen collection. Urine and vaginal specimens collected by patients themselves show a similar cost. Cervical specimens are more expensive since they must be collected by a healthcare professional.
1 Strand displacement amplification (SDA), polymerase chain reaction (PCR).
* Criteria for evidence grading SBU’s conclusions;
Evidence grade 1 – Strong scientific evidence. The conclusion is corroborated by at least two independent studies with high quality, or a good systematic overview.
Evidence grade 2 – Moderately strong scientific evidence. The conclusion is corroborated by one study with high quality, and at least two studies with medium quality.
Evidence grade 3 – Limited scientific evidence. The conclusion is corroborated by at least two studies with medium quality.
Insufficient scientific evidence – No conclusions can be drawn when there are not any studies that meet the criteria for quality.
Contradictory scientific evidence – No conclusions can be drawn when there are studies with the same quality whose findings contradict each other.
SBU Alert is a service provided by SBU in collaboration with the Medical Products Agency, the National Board of Health and Welfare, and the Swedish Association of Local Authorities and Regions.
- Smittskyddsinstitutet, Statistik för klamydiainfektion.
- Atherton H, Banks D, Harbit R, Long L, Chadd F, Hay P, et al. Recruitment of young women to trial of chlamydia screening - as easy as it sounds? Trials 2007;8:41.
- Gabbay M, Thomas J. When free condoms and spermicide are not enough: barriers and solutions to participant recruitment to community-based trials. Control Clin Trials 2004;25:388-99.
- Schachter J. CT and NG: all NAATs are not created equal, Gen-Probe symposia on advances in molecular diagnostic testing for women’s health, Arlanda Conference & Business Center, 2009-10-28, personal communication.
- Michel CE, Sonnex C, Carne CA, White JA, Magbanua JP, Nadala EC Jr, et al. Chlamydia trachomatis load at matched anatomic sites: implications for screening strategies. J Clin Microbiol 2007;45:1395-402.
- Renton A, Thomas BM, Gill S, Lowndes C, Taylor-Robinson D, Patterson K. Chlamydia trachomatis in cervical and vaginal swabs and urine specimens from women undergoing termination of pregnancy. Int J STD AIDS 2006;17:443-7.
- Keane FE, Bendall R, Saulsbury N, Haddon L. A comparison of self-taken vulvovaginal and cervical samples for the diagnosis of Chlamydia trachomatis infection by polymerase chain reaction. Int J STD AIDS 2007;18:98-100.
- Knox J, Tabrizi SN, Miller P, Petoumenos K, Law M, Chen S, et al. Evaluation of self-collected samples in contrast to practitioner-collected samples for detection of Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis by polymerase chain reaction among women living in remote areas. Sex Transm Dis 2002;29:647-54.
- Alary M, Poulin C, Bouchard C, Fortier M, Murray G, Gingras S, et al. Evaluation of a modified sanitary napkin as a sample self-collection device for the detection of genital chlamydial infection in women. J Clin Microbiol 2001;39:2508-12.
- Cook RL, Hutchison SL, Ostergaard L, Braithwaite RS, Ness RB. Systematic review: noninvasive testing for Chlamydia trachomatis and Neisseria gonorrhoeae. Ann Intern Med 2005;142:914-25.
- Blake DR, Maldeis N, Barnes MR, Hardick A, Quinn TC, Gaydos CA. Cost-effectiveness of screening strategies for Chlamydia trachomatis using cervical swabs, urine, and self-obtained vaginal swabs in a sexually transmitted disease clinic setting. Sex Transm Dis 2008;35:649-55.
- Chernesky M, Jang D, Luinstra K, Chong S, Smieja M, Cai W, et al. High analytical sensitivity and low rates of inhibition may contribute to detection of Chlamydia trachomatis in significantly more women by the APTIMA Combo 2 assay. J Clin Microbiol 2006;44:400-5.
- Airell A, Ottosson L, Bygdeman SM, Carlberg H, Lidbrink P, Rudén AK, et al. Chlamydia trachomatis PCR (Cobas Amplicor) in women: endocervical specimen transported in a specimen of urine versus endocervical and urethral specimens in 2-SP medium versus urine specimen only. Int J STD AIDS 2000;11:651-8.
- Fang J, Husman C, DeSilva L, Chang R, Peralta L. Evaluation of self-collected vaginal swab, first void urine, and endocervical swab specimens for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae in adolescent females. J Pediatr Adolesc Gynecol 2008;21:355-60.
- Schachter J, Chernesky MA, Willis DE, Fine PM, Martin DH, Fuller D, et al. Vaginal swabs are the specimens of choice when screening for Chlamydia trachomatis and Neisseria gonorrhoeae: results from a multicenter evaluation of the APTIMA assays for both infections. Sex Transm Dis 2005;32:725-8.
- Haugland S, Thune T, Fosse B, Wentzel-Larsen T, Hjelmevoll SO, Myrmel H. Comparing urine samples and cervical swabs for Chlamydia testing in a female population by means of Strand Displacement Assay (SDA). BMC Womens Health 2010;10:9.
- Falk L, Coble BI, Mjörnberg PA, Fredlund H. Sampling for Chlamydia trachomatis infection - a comparison of vaginal, first-catch urine, combined vaginal and first-catch urine and endocervical sampling. Int J STD AIDS 2010;21:283-7.
- Bakken IJ, Bratt H, Skjeldestad FE, Nordbo SA. [Detection of chlamydia trachomatis in urine, vulval and cervical swabs]. Tidsskr Nor Laegeforen 2005;125:1629-30.
- Skidmore S, Horner P, Herring A, Sell J, Paul I, Thomas J, et al. Vulvovaginal-swab or first-catch urine specimen to detect Chlamydia trachomatis in women in a community setting? J Clin Microbiol 2006;44:4389-94.
- Watson EJ, Templeton A, Russell I, Paavonen J, Mardh PA, Stary A, et al. The accuracy and efficacy of screening tests for Chlamydia trachomatis: a systematic review. J Med Microbiol 2002;51:1021-31.
- Hsieh YH, Howell MR, Gaydos JC, McKee KT Jr, Quinn TC, Gaydos CA. Preference among female Army recruits for use of self-administrated vaginal swabs or urine to screen for Chlamydia trachomatis genital infections. Sex Transm Dis 2003;30:769-73.
- Oakeshott P, Hay P, Hay S, Steinke F, Rink E, Thomas B, et al. Detection of Chlamydia trachomatis infection in early pregnancy using self-administered vaginal swabs and first pass urines: a cross-sectional community-based survey. Br J Gen Pract 2002;52:830-2.
- Serlin M, Shafer MA, Tebb K, Gyamfi AA, Moncada J, Schachter J, et al. What sexually transmitted disease screening method does the adolescent prefer? Adolescents’ attitudes toward first-void urine, self-collected vaginal swab, and pelvic examination. Arch Pediatr Adolesc Med 2002;156:588-91.
- Newman SB, Nelson MB, Gaydos CA, Friedman HB. Female prisoners’ preferences of collection methods for testing for Chlamydia trachomatis and Neisseria gonorrhoeae infection. Sex Transm Dis 2003;30:306-9.
- Chernesky MA, Hook EW 3rd, Martin DH, Lane J, Johnson R, Jordan JA, et al. Women find it easy and prefer to collect their own vaginal swabs to diagnose Chlamydia trachomatis or Neisseria gonorrhoeae infections. Sex Transm Dis 2005;32:729-33.
- Goeree R, Jang D, Blackhouse G, Chong S, Mahony J, Sellors J, et al. Cost-effectiveness of screening swab or urine specimens for Chlamydia trachomatis from young Canadian women in Ontario. Sex Transm Dis 2001;28:701-9.
- Howell MR, Quinn TC, Brathwaite W, Gaydos CA. Screening women for chlamydia trachomatis in family planning clinics: the cost-effectiveness of DNA amplification assays. Sex Transm Dis 1998;25:108-17.
- Chernesky M, Jang D, Smieja M, Portillo E, Ewert R, Pritchard C, et al. Validation of the APTIMA Combo 2 assay for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae in SurePath liquid-based pap test samples taken with different collection devices. Sex Transm Dis 2009;36:581-3.
- Whiting P, Rutjes AW, Reitsma JB, Bossuyt PM, Kleijnen J. The development of QUADAS: a tool for the quality assessment of studies of diagnostic accuracy included in systematic reviews. BMC Med Res Methodol 2003;3:25.