Lee, Seung-eun MPH*†; Nauschuetz, William PHD‡; Jordan, Nikki MPH§; Lindler, Luther PHD*; Steece, Richard PHD¶; Pfau, Esther MPH§∥; Gaydos, Joel MD*
In 2006, the United States reached an unfortunate milestone; more than 1 million Chlamydia trachomatis diagnoses were reported with Neisseria gonorrhoeae trailing behind as the second most common nationally notifiable disease.1,2 Similarly in the US Army, C. trachomatis and N. gonorrhoeae rank as the top two most commonly reported diseases.3 Despite the availability of interventions, for both the US general population and the US military, the prevention of C. trachomatis, N. gonorrhoeae, and other sexually transmitted diseases (STDs) remains a challenge.
The battle against STDs in the US military dates back to the 18th century when the US Army enacted a regulation fining soldiers diagnosed with an STD.4 The US military is disproportionately comprised of a population at high-risk for STDs- nearly one-half (40%) of active component service members are between the ages of 17 to 24 years, compared to approximately one-seventh (14%) of the US civilian population.5,6,7–9 Left untreated STDs, particularly C. trachomatis and N. gonorrhoeae infections, can result in pelvic inflammatory disease which may lead to ectopic pregnancy, infertility, and low birth weight.10,11 The structured environment and universal health care access of the military provide ideal opportunities for military public health programs to intervene among those at highest risk through sex education, behavioral intervention, and screening and treatment programs.
Laboratory diagnosis has been a critical component in the early detection and treatment of STDs.12,13 Presently, an estimated 40 commercial products are Clinical Laboratory Improvement Amendments (CLIA)-compliant for C. trachomatis and N. gonorrhoeae testing, with sensitivities ranging from 50% to 95% and specificities from 95% to 100%.14 However, no routine surveillance systems capture STD laboratory test system information. Due to the increased availability of test products and their varying levels of sensitivity and specificity, defining laboratory testing methodologies becomes important in characterizing disease prevalence, incidence and trends, and subsequently, in guiding disease control policy.12,15
To evaluate laboratory testing practices/methodologies in US Army laboratories in 2007, a questionnaire was distributed to all US Army laboratories. The data from respondents were analyzed to describe the type and volume of STD tests performed in 2007 and to evaluate the results in comparison to similar data published in 2004 for US civilian public health laboratories.
MATERIALS AND METHODS
The Army survey was an adaptation of the Centers for Disease Control and Prevention (CDC) and Association of Public Health Laboratories' (APHL) 2004 Sexually Transmitted Diseases Laboratory Methods Survey.16 As in the CDC-APHL survey, questions addressed the type and volume of C. trachomatis, N. gonorrhoeae, genital herpes, Trichomonas vaginalis, bacterial vaginosis, human papillomavirus, Treponema pallidum (syphilis), and Pap tests performed at the surveyed laboratories during calendar year 2007. Of note, the Army survey only collected information regarding outside laboratory testing for C. trachomatis and N. gonorrhoeae. Additional questions were asked about reporting of laboratory confirmed C. trachomatis and N. gonorrhoeae cases to the responsible Army installation preventive medicine department, the Army's reportable medical events system (RMES), civilian public health departments, and/or the CDC as well as which laboratories participated in the CDC's Gonococcal Isolate Surveillance Project.
Unlike the civilian public health laboratories, the US Army laboratories serve both a clinical and public health function. The US Army medical department is divided into 6 regions: Europe, North Atlantic, Southeast, Great Plains, Western, and Pacific. Each of the 6 regions has a laboratory that offers clinical bacteriology, reference-level testing for mycology, mycobacteriology, virology, molecular assays, and serology assays. The 6 regional laboratories support the community hospitals/laboratories that fall within the same region. The community laboratories offer clinical bacteriology and limited serological assays. For any tests that the community laboratory cannot perform, they may send their specimens to their regional laboratory, commercial reference laboratory, or a state public health laboratory for testing. The survey was emailed to all 38 US Army regional and community laboratories (31 in the United States, 7 outside the continental United States) by the US Army's clinical laboratory coordinator for biopreparedness. Laboratory directors were asked to return the completed survey by e-mail. Follow-up and inquiries for further clarification on survey question responses were conducted via e-mail or phone call. The results of the survey were compared across Army laboratories and to US civilian public health laboratories.
Of 38 survey recipients, 35 (92%) completed and returned the survey and 3 (8%) did not. Among the 35 returned surveys, 29 were from a US installation, with 16 from the South, 7 from the West, 3 from the Midwest, and 3 from the Northeast. Six were from laboratories outside the continental United States, including 4 from Europe and 2 from Asia.
C. trachomatis and N. gonorrhoeae Testing
Among 35 laboratories, 17 (48.6%) tested specimens on-site and 18 (51.4%) sent specimens to the nearest Army laboratory with relevant testing capability. Six of the 17 Army laboratories with internal testing capability served as the main testing sites for the remaining 18 laboratories that did not test specimens on-site; 1 Navy hospital laboratory served as the testing site for an Army installation.
Overall, 200,772 (78.6%) of C. trachomatis and 202,181 (77.2%) of N. gonorrhoeae specimens were tested by nucleic acid amplification tests (NAATs); and 54,737 (21.4%) and 59,872 (22.8%), respectively, were tested by non-NAATs (Tables 1, 2). Approximately 62% and 16% of C. trachomatis and N. gonorrhoeae specimens were tested using transcription-mediated amplification and DNA hybridization probe, respectively. Of all NAAT and non-NAAT test types, the GEN-PROBE Aptima (Gen-probe, Inc., San Diego, CA) C. trachomatis/N. gonorrhoeae combo assay using the automated TIGRIS (Gen-probe, Inc., San Diego, CA) system was reported to be used most frequently.
In 2007, a majority of US Army laboratories were using C. trachomatis test methods other than culture. This is in contrast to the US civilian public health laboratories in 2004, in which 15 (13.9%) of laboratories were still culturing specimens. Compared to the US civilian public health laboratories, NAATs were used more frequently in US Army laboratories (64.4% vs. 78.6%). Similarly for N. gonorrhoeae, approximately 202,181 (77.2%) of N. gonorrhoeae specimens in U.S. Army laboratories were tested using NAAT technology, specifically transcription mediated amplification and strand displacement assay, compared to 2,106,055 (60.8%) in US public health/civilian laboratories. For 2 US Army laboratories that reported using more than 1 test type for C. trachomatis testing, there appeared to be a shift towards exclusive use of NAATs in the latter part of the year. This trend toward NAATs, for both C. trachomatis and N. gonorrhoeae testing, coincided with reports from civilian public health laboratories.16,17
Of 17 (48.6%) laboratories that used culture as a method of N. gonorrhoeae testing, 10 performed antimicrobial susceptibility testing on N. gonorrhoeae specimens and 7 did not. Among the 10 who performed antimicrobial susceptibility testing in 2007, 9 reported using the β-lactamase test, 2 reported using the disk diffusion test, and 1 reported using the E-test. Two of the laboratories reported having used 2 types of tests—1of the laboratories with the E-test and β-lactamase test and the second laboratory with the disk diffusion and β-lactamase tests. The antimicrobials tested included macrolides, β-lactams, tetracyclines, and quinolones. The laboratories that performed both culture and another test for N. gonorrhoeae testing did not perform both tests on all N. gonorrhoeae specimens.
Other STD Testing
In 2007, 33 (94.3%) of 35 laboratories reported testing for genital herpes (HSV), trichomonas, bacterial vaginosis, syphilis, human papillomavirus (HPV), and/or premalignant/malignant cervical cells (Pap test) (Table 3). The nontreponemal and treponemal syphilis tests used most commonly were the RPR-qualitative, RPR-quantitative, FTA-ABS, and TP-PA. None of the laboratories reported having performed any direct detection tests for syphilis. Only 3 laboratories reported using rapid point-of-care tests to diagnose trichomonas and/or vaginosis cases; 2 laboratories reported using the Affirm VPIII (Becton, Dickinson, and Co., Sparks, MD), and 1 laboratory did not report the type of point-of-care test used. Overall, the Pap, at 332,335 tests, was the most frequently used test followed by syphilis with 125,960 tests. Compared to C. trachomatis at 225,209 tests or N. gonorrhoeae at 262,053 tests, the frequency of Pap tests exceeded both.
Testing for herpes was reported more frequently in civilian public health laboratories than in the US Army but Army figures may be an underestimate because Army laboratories may have referred their specimens to another laboratory for testing. In contrast to civilian public health laboratories, the majority of which were performing cultures, US Army laboratories were performing direct detection tests.16
For syphilis testing, 27 (81.8%) of US Army laboratories were using either nontreponemal and/or the treponemal tests. In civilian public health laboratories, although nontreponemal and treponemal tests constituted most of the syphilis testing, 31 (27.2%) of civilian public health laboratories still performed direct detection tests.
The US Army has a long history of tracking diseases and conditions of public health and military importance. Starting in 1998, tracking has been done through the RMES.18 C. trachomatis, N. gonorrhoeae, and syphilis have been reportable diseases since RMES was initiated. Similar to the CDC's National Notifiable Diseases Surveillance System, in the US Army, diseases and conditions that meet predetermined case definitions are reported to their local installation's public health assets.19,20 The installation's preventive medicine department confirms that case definitions are met and ensures cases are reported through the RMES.21 Positive results are also forwarded to the local civilian health department by the local installation preventive medicine department as required by state law.
All 35 laboratories reported that positive C. trachomatis and N. gonorrhoeae results were reported to local installation preventive medicine departments. Additionally, 1 of the 35 laboratories reported participation in the CDC's Gonococcal Isolate Surveillance Project in 2007.
Before the implementation of antigen, nucleic acid, or point-of-care detection tests, it took an average of 3 to 7 days to confirm a C. trachomatis diagnosis.22 Although the nearly 100% specificity with culture when testing a low prevalence population was desirable, the requirement of technical expertise, delay between specimen collection and confirmation, and/or high number of viable organisms necessary for detection has made it a less desirable test over the years.22,23 Health care providers need access to results that are valid, reliable and timely to properly treat STDs and reduce disease transmission. In the last 15 years, recent technologies have filled that void, providing greater sensitivity and comparable specificity when compared with culture. The results from this 2007 survey, the first survey to look at STD laboratory methods in the US Army, demonstrated high utilization of these newer and more sensitive technologies.
Despite the widespread use of NAATs for C. trachomatis and N. gonorrhoeae confirmation in US Army laboratories, N. gonorrhoeae culture was still performed by nearly one-half of US Army laboratories. The aforementioned high proportion of laboratories that still prefer culture is encouraging. The proportion of laboratories that perform cultures for N. gonorrhoeae should be increased if possible and monitored given continued challenges with N. gonorrhoeae antimicrobial resistance.24
For syphilis diagnosis, it is recommended that a combination of serologic tests be performed if a direct detection test is not performed.19,20,6 In the US Army, only 8 laboratories performed a combination of nontreponemal and treponemal tests; 21 laboratories performed only a nontreponemal or a treponemal test. Similarly to herpes testing, the survey did not ask about referral of specimens to a reference laboratory for testing. Due to this limitation, whether the 21 Army laboratories met the CDC's recommended guidelines for syphilis testing cannot be evaluated.
The high volume of Pap testing in comparison to C. trachomatis or N. gonorrhoeae testing was observed. This may be explained by current screening and testing recommendations. Current US Preventive Services Task Force (USPSTF) screening recommendations for C. trachomatis and N. gonorrhoeae call for sexually active women under the age of 24 years or younger or women at high risk be tested.9,25 For cervical cancer, US Preventive Services Task Force recommends that sexually active women are tested.26 The recommendation for cervical cancer test may allow a larger number of female Army service members to become eligible to test in comparison to the recommendations for C. trachomatis or N. gonorrhoeae.
In a population with reported C. trachomatis prevalences of approximately 10% for female Army recruits and 5% for male Army recruits, the opportunities for prevention and treatment of STDs are many, and the foundation for these efforts are accurate and timely laboratory testing.27,28 The development of NAATs in the last few years have not only changed how health care providers screen patients but how burden of STDs are interpreted. NAATs have shown to have a sensitivity greater than that of culture at 90 to 95% sensitivity and specificity similar to that of culture at 98% to 100%.15 In addition, NAATs can be used with first-catch urine, a specimen that is easier to collect and that is noninvasive.13
The results of this survey indicate that most US Army laboratories have adopted many of the best technologies available to identify C. trachomatis and N. gonorrhoeae infections in their populations.29,30 Data gathered from surveillance systems such as the RMES and National Notifiable Diseases Surveillance System are not without limitations, but given the high use of NAATs for C. trachomatis and N. gonorrhoeae in US Army laboratories, rates and trends of these infections can be analyzed with more confidence than with a test that has a lower sensitivity. The same cannot be said for some of the other STDs with tests of lower sensitivity and specificity.
Our survey has several limitations. The time difference in survey data acquisition between the CDC-APHL and US Army laboratory surveys limits comparison. However, the opportunity to make broad comparisons was possible. Three of the Army laboratories did not respond to the survey which may bias our results. But given that the 3 laboratories were the smaller community laboratories and not regional laboratories, we feel that the type and volume of tests in the 3 laboratories would not affect our overall results. The survey did not ask about specimen referral for the other STDs tests therefore we could not assess whether laboratories met the CDC's recommended guidelines for testing. Future surveys should address specimen referral so that testing guidelines can be evaluated. Finally, the survey only addressed Army laboratories therefore laboratory testing practices at other military Services could not be assessed.
Some of the recommendations by Niebuhr et al for enhancing STD control in the military called for greater collaboration among the military Services as well as the military and civilian public health communities.31 Specifically, the recommendations called for the collaboration of the military Services in negotiating better prices for STD tests. The results of our survey have shown that the type of tests and systems are fairly consistent from 1 Army installation to another. There is potential that results are similar for the other Services as well. It is appropriate then to consider recurring surveys of US Army laboratories and the laboratories of other US military services to better determine test type and volume. Another recommendation called for the consideration of military and civilian STD programs in cost sharing. Given the high prevalence of STDs at the start of military recruit training and that 15% of US Army recruits return to civilian life within 1 year, the burden of disease is passed from civilian to military and back to civilian programs.27,32,33 A survey addressing both military and civilian laboratories could determine how the costs of tests could be shared. Finally, given the common use of NAATs in Army laboratories and the cost and health outcome benefits in screening men, considerations should be given to screening this population.34
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