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Limitations of Screening Tests for Asymptomatic Chlamydia
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Am Fam Physician. 2005 Jan 1;71(1):172-174.
One of the most frequently reported infectious diseases is Chlamydia, which can cause significant reproductive morbidity in women. The prevalence of chlamydial infections in adolescent and young adult women in the United States ranges from 5 to 27 percent, placing this age group at the highest risk for this infection. Various organizations have recommended screening asymptomatic young women for chlamydial infections. The goal of this screening should be to find the test that is least invasive and most acceptable for patients and health care professionals. The nucleic acid amplification tests can detect Chlamydia on genital secretions, urine specimens, and endocervical or urethral samples. These tests have been assessed in high-risk populations on symptomatic and asymptomatic patients. Shrier and associates evaluated the different test types, specimen sources, and collection methods for Chlamydia screening in asymptomatic female adolescents and young adults. In addition, they assessed the way sexual history and clinical findings affect the prediction of chlamydial infections.
Participants in the study included female patients from 16 to 25 years of age who were examined at two outpatient centers for routine gynecologic care. They were excluded from the study if they reported any symptoms consistent with a sexually transmitted disease (STD), were pregnant, had taken antibiotics within the past 21 days, had a chlamydial infection within the past six weeks, or were sexual partners with someone known to have an STD.
Participants were interviewed about their sexual history using a standardized format. Specimen collection started with two swabs inserted into the vagina by the participants and collection of the first 30 mL of voided urine. During the pelvic examination, specimens were collected from the distal urethra, vaginal area, and endocervical canal. Testing included cultures for Chlamydia and gonorrhea, and polymerase chain reaction, ligase chain reaction, and nucleic acid amplification tests.
Out of 139 participants, all nine test results were available for 126 participants. The prevalence of Chlamydia infection in the study population was 22 percent. The sensitivities for the polymerase chain reaction and ligase chain reaction were similar, but the urine polymerase chain reaction test had a lower sensitivity. The specificities for each of the tests were 99 to 100 percent, but the urine polymerase chain reaction test’s specificity was 91 percent. The positive predictive values for the tests were higher than 93 percent except for the urine polymerase chain reaction test, which was 65 percent. The negative predictive values for all of the tests were 83 to 91 percent. Combining two tests from two different specimens improved sensitivities without having a negative impact on the specificities.
The authors conclude that the sensitivity of one test from one specimen is less than was previously reported. They add that when screening for Chlamydia infection in asymptomatic adolescents and young adults, the limitations of one test type at one site must be considered.
Shrier LA, et al. Limitations of screening tests for the detection of Chlamydia trachomatis in asymptomatic adolescent and young adult women. Am J Obstet Gynecol. March 2004;190:654–62.
Copyright © 2005 by the American Academy of Family Physicians.
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