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Approach ConsiderationsBecause of the possibility of multiple sexually transmitted infections, all patients with any sexually transmitted disease (STD) should be evaluated for chlamydial infection. Endocervical, urethral, rectal, or oropharyngeal specimens should be obtained and assayed for C trachomatis infection in both males and females based on the patient’s sexual practices obtained by history. [32] A voided urine sample, whether midstream or first-void, effectively captures the chlamydial organism for nucleic acid amplification testing (NAAT). [33] NAATs are the most sensitive tests for these specimens and are therefore recommended for detecting C trachomatis infection. [34, 35] Self-collected vaginal swab specimens are equivalent in sensitivity and specificity to those collected by a clinician using NAATs. [34, 36, 37] In infants with suspected chlamydial pneumonia, perform a nasopharyngeal swab for Chlamydia culture. Currently available rapid tests [38] are not approved for use on such specimens. In severe or complicated cases, consider sending bronchoalveolar lavage fluid for chlamydial culture as well. A complete blood count (CBC) revealing peripheral eosinophilia in the appropriate clinical situation is additional evidence supporting C trachomatis pneumonia. In infants with suspected chlamydial conjunctivitis, perform an antigen/DNA detection test, chlamydial culture, or both, using scrapings from the palpebral conjunctiva. If the mother had a documented chlamydial infection during pregnancy that was untreated, presumptively treat the infant, even without confirmation of infection.  Basic Laboratory StudiesA complete blood count (CBC) can be performed for suspected pelvic inflammatory disease (PID). The following should also be considered:
A pregnancy test is mandatory for females with suspected chlamydial infection. Obtaining a pregnancy test helps with early diagnosis and guidance of treatment. Because pregnancy is a contraindication for the use of doxycycline and ofloxacin, it is critical to obtain a pregnancy test before beginning treatment with these drugs. Cytology and Cell CultureCytology is used mainly for diagnosing infant inclusion conjunctivitis and ocular trachoma through the demonstration of intracytoplasmic C trachomatis inclusions in HeLa cells (ie, continuously cultured carcinoma cell line used for tissue cultures). Cytologic diagnosis also is used to evaluate endocervical scrapings, but interpretation is difficult, and sensitivity and specificity have been low. C trachomatis grows well in a variety of cell lines (eg, McCoy and HeLa cells) that can be maintained in tissue culture. Incubation in tissue culture is 40-72 hours, depending on the cell type and specific biovar. Intracytoplasmic inclusions can be detected either by Giemsa stains or by immunofluorescent staining with monoclonal antibodies. Cultures are difficult to obtain; many false-negative results are returned. They are also expensive to perform, because of the expertise and laboratory resources required. In addition, they are unsuitable for large numbers of patients (eg, in the emergency department [ED]). Nevertheless, in certain clinical situations, cultures are mandatory. Because of its high specificity (100%) and sensitivity, cell culture is the only test that should be used to establish the presence or absence of infections in cases with legal implications, such as those involving rape or sexual abuse. Cell culture is also preferred for rectal specimens because nonculture test results are difficult to interpret in the presence of stool organisms. Molecular Techniques for Detecting Antigen, DNA, or RNA/Rapid TestsBecause C trachomatis grows only within columnar cells, obtaining a specimen that contains cells directly from the urethra or cervix, not on pooled vaginal secretions, is important. In obtaining cells along with discharge, attempt to apply pressure to the inside of the cervix or urethra. In males, insert collection swabs 1-2 cm into the urethra after the urethra is milked to bring down secretions. Always follow the directions of the manufacturer of the kit used for collection, and follow transport instructions. Direct fluorescent antibody (DFA) testing is a laboratory assay for C trachomatis that has a sensitivity of 50-80% and a specificity of 99% specificity. It is the method of choice for confirming other assays. However, it is labor intensive and requires skilled personnel. Enzyme-linked immunosorbent assay (ELISA) is a laboratory assay for C trachomatis that has a sensitivity of 40-60% and a specificity of 99%. Because it is both automatable and cost-effective, it is suitable for large numbers of patients. ELISA is the most commonly used test for Chlamydia in the emergency department (ED) and in outpatient clinics. Detection of chlamydial DNA may be accomplished by using specific probes. Newer DNA probe kits currently are available that allow detection of C trachomatis and N gonorrhoeae from voided urine specimens, obviating the need for direct sampling in uncomplicated cases. These urine tests may also be appropriate for use in the evaluation of possible sexual abuse. [39] The US Food and Drug Administration (FDA) recently cleared the Cepheid GeneXpert CT/NG (Xpert) rapid polymerase chain reaction (PCR) test as a moderate-complexity test. CT/NG GeneXpert is a real-time PCR assay that can be run on demand in less than 2 hours and has a test performance that is similar to that of existing nucleic acid amplification tests (NAATs) in both low- and high-prevalence populations. [40] The C trachomatis nonculture tests have been largely replaced because of the superior performance of NAATs, even when performed on noninvasive specimens. Nucleic Acid Amplification TestsNAATs have become the preferred diagnostic and screening test for C trachomatis genital infection in the United States because they are sensitive and can be used for noninvasive testing without the need for a pelvic examination or a urethral swab. [41, 42, 43] NAATs target and amplify conserved nucleic acid sequences that are present in almost all clinical strains of C trachomatis, including the genital, LGV, and ocular serovars. The APTIMA Combo 2 Assay for ribosomal RNA (rRNA) can be used on ThinPrep liquid-based Pap smear specimens. [44] This has the advantage of being relatively simple and inexpensive. Most studies report sensitivities greater than 70% and specificities of 97-99% in populations of men and women with a prevalence of infection of 5% or more. If a definitive diagnostic test is required, antigen detection may well be the most appropriate diagnostic test for a primary care setting in the United States. The main disadvantage of this approach is that it is less sensitive than tissue culture. In populations with a low (< 5%) prevalence of chlamydial infection, a highly significant percentage of positive test results are false positives. Accordingly, verification of a positive test result is desirable in certain cases. Such verification can be achieved by means of culture (eg, a second nonculture test that identifies a different chlamydial antigen or nucleic acid sequence from that identified in the first test), a blocking antibody, or a competitive probe. NAATs that are cleared by the FDA are recommended for detection of genital tract infections caused by C trachomatis and N gonorrhoeae in men and women with or without symptoms. [45] Older nonculture tests and non-NAATs have inferior sensitivity and specificity characteristics and are no longer recommended. NAATs have not been cleared by FDA for the detection of rectal and oropharyngeal infections caused by C trachomatis. The Centers for Disease Control and Prevention (CDC) recommends NAATs to test for these extragenital infections based on increased sensitivity, ease of specimen transport, and processing. Routine repeat testing of NAAT-positive genital tract specimens is not recommended because the practice does not improve the positive predictive value of the test. C trachomatis and N gonorrhoeae culture capacity might still be needed in instances of child sexual assault in boys and extragenital infections in girls. [45] Although NAATs are sensitive, numerous disadvantages have been discussed. The first is that they are expensive and thus may not be affordable by health departments for comprehensive screening. [46] Another disadvantage is that the FDA-approved NAATs cannot distinguish LGV from non-LGV strains, which is important because the duration of treatment is longer for LGV infections. In addition, NAATs detect chlamydial DNA or RNA rather than live organisms, and positive NAAT results are not uncommon 3 weeks after completion of antibiotic therapy. [47] Thus, NAATs should not be used as a test-of-cure assay, except in pregnant women in whom it is justified to document cure at 3-4 weeks after completion of therapy in an effort to prevent infection in the infant. [41] SerologyOn a complement fixation test, all patients with lymphogranuloma venereum (LGV) have complement-fixing antibody titers higher than 1:16. Fifteen percent of men with urethritis and 45% of women with endocervical infection have titers of 1:16 or greater. The microimmunofluorescence test is more sensitive than the complement fixation test. Results are positive in at least 99% of women with cervicitis and in 80-90% of men with urethritis. Antichlamydia immunoglobulin M (IgM) is uncommon in adults with genital tract infection. The prevalence of antichlamydial immunoglobulin G (IgG) is high in sexually active adults, even in those who do not have an active infection, and it likely is due to past infection. A statistically significant association exists between chlamydia-specific serum immunoglobulin A (IgA) and active disease. The sensitivity, specificity, and predictive values of serologic studies for Chlamydia are not high enough to make any of them clinically useful in the diagnosis of active disease. Therefore, chlamydial serologies are not recommended for diagnosis of genital tract disease. The choice of the most appropriate test depends on the clinical setting, the facilities available, and the relative cost. CT, Radiography, and UltrasonographyImaging studies are usually not required for patients with uncomplicated genital chlamydial infections. However, computed tomography (CT) and ultrasonography are useful diagnostic adjuncts in cases of complicated (upper tract) infection. For example, CT may identify Fitz-Hugh-Curtis syndrome (perihepatitis; see the images below). Ultrasonography may be performed to look for tubo-ovarian abscess. Obtain a chest radiograph for infants with suspected pneumonia. Chlamydial pneumonia may appear as a lobar or interstitial pneumonia in infants. ScreeningThe US Preventive Services Task Force recommends routine Chlamydia screening for sexually active young women to prevent consequences of untreated chlamydial infection (eg, PID, infertility, ectopic pregnancy, and chronic pelvic pain). [5] Less than 50% of young, sexually active females in the United States are screened for Chlamydia. Nationally, the annual screening rate increased from 25.3% in 2000 to 43.6% in 2006, then decreased slightly to 41.6% in 2007. [5] A guideline synthesis that addresses screening recommendations is also available from the National Guideline Clearinghouse. [8] As a screening measure for asymptomatic males only, obtain urine for a leukocyte esterase test. This looks for white blood cells (WBCs), which are virtually diagnostic of chlamydial infection or gonorrhea in the absence of urinary tract infection (UTI) symptoms. If the leukocyte esterase test result is positive, proceed with the usual diagnostic tests.
Author Specialty Editor Board Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference Disclosure: Received salary from Medscape for employment. for: Medscape. Chief Editor Michael Stuart Bronze, MD David Ross Boyd Professor and Chairman, Department of Medicine, Stewart G Wolf Endowed Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center; Master of the American College of Physicians; Fellow, Infectious Diseases Society of America; Fellow of the Royal College of Physicians, London Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Medical Association, Association of Professors of Medicine, Infectious Diseases Society of America, Oklahoma State Medical Association, Southern Society for Clinical Investigation Disclosure: Nothing to disclose. Acknowledgements Jeffrey Blitstein, MD Staff Physician, Department of Internal Medicine, Division of Infectious Disease, VA New York Harbor Health Care System at Brooklyn Disclosure: Nothing to disclose. Marc James Grella, MD Clinical Instructor, Department of Pediatrics, Massachusetts General Hospital Marc James Grella, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American Medical Association, and Massachusetts Medical Society Disclosure: Nothing to disclose. Jonathan A Handler, MD HSG Chief Deployment Architect, Microsoft Corporation, Adjunct Associate Professor, Department of Emergency Medicine, Northwestern University, Feinberg School of Medine Jonathan A Handler, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine Disclosure: Nothing to disclose. Renuka Heddurshetti, MD Fellow in Infectious Diseases, Department of Internal Medicine, State University of New York at Brooklyn Renuka Heddurshetti, MD is a member of the following medical societies: American College of Physicians and Infectious Diseases Society of America Disclosure: Nothing to disclose. Debra E Houry, MD, MPH Director, Center for Injury Control, Associate Professor of Emergency Medicine, Department of Emergency Medicine, Emory University Debra E Houry, MD, MPH is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, American Public Health Association, and Society for Academic Emergency Medicine Disclosure: Nothing to disclose. Rhett L Jackson, MD Associate Professor and Vice Chair for Education, Department of Medicine, Director, Internal Medicine Residency Program, University of Oklahoma College of Medicine; Assistant Chief, Medicine Service, Oklahoma City Veterans Affairs Hospital Rhett L Jackson, MD is a member of the following medical societies: American College of Physicians-American Society of Internal Medicine and American Medical Association Disclosure: Nothing to disclose. Ashir Kumar, MD, MBBS, FAAP Professor Emeritus, Department of Pediatrics and Human Development, Michigan State University College of Human Medicine Ashir Kumar, MD, MBBS, FAAP is a member of the following medical societies: American Association of Physicians of Indian Origin and Infectious Diseases Society of America Disclosure: Nothing to disclose. Richard Lavely, MD, JD, MS, MPH Lecturer in Health Policy and Administration, Department of Public Health, Yale University School of Medicine Richard Lavely, MD, JD, MS, MPH is a member of the following medical societies: American College of Emergency Physicians, American College of Legal Medicine, and American Medical Association Disclosure: Nothing to disclose. John M Leedom, MD Professor Emeritus of Medicine, Keck School of Medicine of the University of Southern California John M Leedom, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians-American Society of Internal Medicine, American Society for Microbiology, Infectious Diseases Society of America, International AIDS Society, and Phi Beta Kappa Disclosure: Nothing to disclose. Larry I Lutwick, MD Professor of Medicine, State University of New York Downstate Medical School; Director, Infectious Diseases, Veterans Affairs New York Harbor Health Care System, Brooklyn Campus Larry I Lutwick, MD is a member of the following medical societies: American College of Physicians and Infectious Diseases Society of America Disclosure: Nothing to disclose. Mark R Schleiss, MD American Legion Chair of Pediatrics, Professor of Pediatrics, Division Director, Division of Infectious Diseases and Immunology, Department of Pediatrics, University of Minnesota Medical School Mark R Schleiss, MD is a member of the following medical societies: American Pediatric Society, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, and Society for Pediatric Research Disclosure: Nothing to disclose. Russell W Steele, MD Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association Disclosure: Nothing to disclose. Kelley Struble, DO Fellow, Department of Infectious Diseases, University of Oklahoma College of Medicine Kelley Struble, DO is a member of the following medical societies: American College of Physicians and Infectious Diseases Society of America Disclosure: Nothing to disclose. Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference Disclosure: Medscape Salary Employment Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference Disclosure: Nothing to disclose. Which one of the following tests is preferred for detecting Chlamydia trachomatis in men?NAAT assays are recommended for detection of urogenital infections caused by C. trachomatis and N. gonorrhoeae infections in women and men with and without symptoms.
What type of test is used to detect chlamydia?How does a chlamydia test work? The most commonly used type of chlamydia test is called a Nucleic Acid Amplification Test (NAAT). A NAAT detects the DNA of the bacteria that cause the chlamydia infection. You provide a sample of urine.
What is the best method for detection of Chlamydia trachomatis?Nucleic acid amplification tests are the most sensitive tests for detecting chlamydia infection, and may be performed on endocervical, urethral, vaginal, pharyngeal, rectal, or urine samples.
Why is PCR a preferred diagnostic test for chlamydia?Polymerase chain reaction is a good diagnostic tool for sexually transmitted infections because it has a high sensitivity and specificity. Chlamydia trachomatis is the most frequent sexually transmitted infection, followed by Neisseria gonorrhoeae.
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Which one of the following tests is preferred for detecting Chlamydia trachomatis?
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