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Prevention of Pelvic Inflammatory Disease (PID): Screening for Chlamydia trachomitis and Neisseria gonorrhoeae
- Interpretive Guide
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Clinical Focus |
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Prevention of Pelvic Inflammatory Disease (PID) |
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| Screening for Chlamydia trachomatis and Neisseria gonorrhoeae | |
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Pelvic inflammatory disease (PID) is one of the most common complications of sexually transmitted infections in women. It affects various structures of the upper female genital tract, leading to disorders such as endometritis, salpingitis, tubo-ovarian abscess, and pelvic peritonitis.1 In the United States PID affects about 750,000 women each year, causing infertility in about 10% to 15% of affected women.2 It can lead to chronic pelvic pain and is also a major cause of ectopic pregnancy.2 PID presents with a wide clinical spectrum and often goes undetected because signs and symptoms are non-specific; therefore, a low threshold for diagnosis should be maintained.1 PID is often caused by sexually transmitted organisms, most commonly Chlamydia trachomatis and Neisseria gonorrhoeae. Other causative organisms include constituents of vaginal flora, such as anaerobic bacteria, Gardnerella vaginalis, Haemophilus influenzae, enteric gram-negative rods, and Streptococcus agalactiae.2,3 Cytomegalovirus, Mycoplasma hominis, Mycoplasma genitalium, and Ureaplasma urealyticum have also been implicated as causative agents.1-4 Chlamydia and gonorrhea are the 2 most common reportable sexually transmitted infections in the United States.5 Each year an estimated 2.9 million new C trachomatis infections occur among adolescents and adults in the United States6; N gonorrhoeae is responsible for an estimated 820,000 new infections annually.6 These diseases affect both men and women and are often spread unknowingly by asymptomatic individuals. Infection during pregnancy may result in neonatal transmission, leading to complications such as ophthalmia neonatorum and pneumonia. Cure rates for chlamydial infection are about 97% to 98% with a 7-day, multidose regimen of doxycycline or a single dose of azithromycin.7 N gonorrhoeae also responds well to treatment, although resistance to beta-lactams, fluoroquinolones, and oral cephalosporins can complicate response. Fluoroquinolones are not recommended for treatment of gonorrhea, and oral cephalosporins are no longer recommended as a first-line therapy.8 Because chlamydia is common in patients with gonorrhea, cotreatment should be considered in individuals with diagnosed gonorrheal infection.8 See Centers for Disease Control and Prevention (CDC) guidelines for currently recommended treatment regimens.8 Current guidelines recommend N gonorrhoeae and C trachomatis testing, as well as HIV screening, for all women with PID.1 Conversely, screening for N gonorrhoeae and C trachomatis may also aid in detecting subclinical PID or avoiding progression to PID. Subclinical PID has been reported in >25% of women with gonorrhea or chlamydia9; some studies have indicated that up to 40% of women with untreated chlamydia develop PID.10 Because most people with C trachomatis infection are asymptomatic and are not aware of their infection, screening is important if these infections are to be adequately diagnosed and treated. Chlamydia screening among asymptomatic, sexually active women can decrease the incidence of PID11 and, possibly, the prevalence of chlamydial infection. Screening for cervical C trachomatis infection in asymptomatic women can be cost effective. Screening with a DNA amplification assay, coupled with a single dose of azithromycin in positive patients, was reported to be a cost-effective strategy when the prevalence is 6% or greater.12 Screening high-risk women and treating those infected was found to significantly lower the incidence of PID relative to a control population (9/1009 [0.9%] vs 33/1598 [2.1%], respectively).11 Similarly, an economic evaluation of a school-based sexually transmitted infection program in New Orleans revealed a savings of $1524 for each case of PID prevented.13 Thus, timely detection followed by effective therapy appears to be a cost-effective way of preventing complications and further spread of C trachomatis infection. Guidelines from the CDC now recommend routine annual chlamydia screening for all sexually active women under 25 years of age and for all women at increased risk.1 Moreover, because repeat infection is common in women with chlamydia, retesting should be considered about 3 to 4 months after treatment.1 Targeted gonorrhea screening among sexually active women at high risk for infection is also recommended (see “Individuals Suitable for Testing” below).14 |
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Individuals Suitable for Testing1,14,15 [return to contents] |
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Nucleic Acid Amplification Tests |
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Non-nucleic Acid Tests |
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Chlamydia Screening and Diagnosis Culture is no longer the standard for diagnosis of C trachomatis infection. With the advent of nucleic acid amplification and detection methods, culture is used infrequently because of higher cost, specimen viability requirements during collection and transport, and slow turnaround time (3–7 days). Culture continues to be the most specific method (~100%), followed closely by nucleic acid amplification assays. The remaining methods range from 97% to 99% specific, depending on the study. The CDC recommends nucleic acid amplification tests for detecting infection of the reproductive tract in both men and women, regardless of symptoms.1 Non-culture tests for C trachomatis are more rapid and standardized and have less stringent specimen handling requirements. Nucleic acid amplification tests such as SDA and TMA are the most sensitive methods for detecting C trachomatis.1 Compared with amplification methods, culture is only 70% to 85% sensitive.16,17 The remaining tests are all less sensitive than culture (sensitivity roughly 70%7–97% that of culture, depending on reagent manufacturer and specimen type). Chlamydia Test-of-Cure Routine test-of-cure is not recommended for chlamydia when first-line regimens are used.1 When test-of-cure is indicated, as in the case of chlamydial infection during pregnancy, nucleic acid amplification testing should be performed 3 weeks post-therapy.1 Non-culture detection methods should not be used <3 weeks after treatment is completed.1 Gonorrhea Nucleic acid amplification testing of endocervical, vaginal, male urethral, or urine specimens can be used to detect of gonorrhea affecting the genitourinary system.1 Culture and antimicrobial susceptibility testing should also be performed when treatment failure is suspected.1 As with chlamydia testing, nucleic acid amplification assays for gonorrhea offer convenience and high sensitivity. The difference in sensitivity between culture and nucleic acid amplification methods is less pronounced than with chlamydia, although inappropriate storage and transport conditions can lessen the sensitivity of culture. SDA has shown specificity similar to that of culture and greater sensitivity).18 TMA also exhibits excellent specificity (99% in swabs and urine) and sensitivity (99% in swabs, 91% in urine).19 |
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Positive results are considered evidence of infection. Because of the high specificity of available molecular tests, confirmatory testing is generally not necessary.20 However, in low prevalence populations or in a case where a positive may have severe socio-legal ramifications, testing with an alternate method or target is recommended. Individuals positive for one STI should be tested for others. Chlamydia Antibody tests: C trachomatis infection confers little immunity against reinfection, although secretory IgA may provide some protection. A positive IgM antibody result may indicate recent infection with C trachomatis; a negative result, however, does not indicate absence of C trachomatis since IgM antibodies are frequently absent in infected individuals. The presence of IgG indicates active or resolved infection. High IgG titers often point to recent infection, whereas intermediate or low titers may be due to early infection, resolved infection, or cross-reaction with other Chlamydia species. When comparing antibody tests, a 4-fold rise in titer best indicates active infection. Serologic tests are not recommended for chlamydia screening.3 Culture: A positive culture result is highly specific for C trachomatis. A negative result may indicate absence of C trachomatis infection or a false-negative due to lack of organism viability or improper specimen collection. DFA: A positive DFA result indicates the presence of C trachomatis infection, whereas a negative result implies absence of infection or a false-negative due to lack of assay sensitivity. RNA, TMA: A positive TMA result is highly indicative of C trachomatis infection, while a negative result is highly indicative of lack of infection. False-positive results may be obtained due to laboratory contamination (rare in an experienced lab) or sampling too soon after cessation of therapy (ie, <3 weeks post-therapy). DNA, SDA: A positive DNA result is highly indicative of C trachomatis infection. False-positive results may be obtained due to laboratory contamination (rare in an experienced lab) or sampling too soon after cessation of therapy (ie, <3 weeks post-therapy). Negative results are highly specific for lack of C trachomatis infection but may be caused by interfering substances. Gonorrhea Culture: A positive culture result is highly specific for N gonorrhoeae. A negative result may indicate absence of infection or a false-negative due to lack of organism viability or improper specimen collection. DNA, SDA: A positive test result strongly suggests N gonorrhoeae infection. False-positive results may be obtained due to laboratory contamination (rare in an experienced lab) or sampling too soon after cessation of therapy (ie, <3 weeks post-therapy). Negative results are highly specific for absence of N gonorrhoeae infection but may be caused by interfering substances. RNA, TMA: A positive TMA result is highly indicative of N gonorrhoeae infection, while a negative result is highly indicative of lack of infection. False-positive results may be obtained due to laboratory contamination (rare in an experienced lab) or sampling too soon after cessation of therapy (ie, <3 weeks post-therapy). |
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07/2013 |
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