GENITAL CHLAMYDIA TRACHOMATIS INFECTION, a leading notifiable infectious condition in the United States with an estimated 3 million new cases each year, causes urethritis, cervicitis, endometritis, salpingitis, and pelvic inflammatory disease. These infections have also been associated with adverse reproductive outcomes such as infertility, miscarriage, and ectopic pregnancy. 1,2 3 C. trachomatis has also been shown to increase the risk of acquisition and transmission of human immunodeficiency virus (HIV) and could be a risk factor for the development of cervical cancer. 4,5
During the past decade, the introduction of nucleic acid amplification tests (NAATs) for detection of chlamydial infections has resulted in enormous improvement in diagnostic sensitivity. 6 6,7 C. trachomatis infections are highly prevalent among young, sexually active people. 8–13 17-19
In clinics, schools, and home settings, use of urine specimens for the diagnosis of chlamydial infections has received high marks for acceptability. 14-16 20-26 26-29 26,30,31
However, the sensitivity and specificity of SAS for detection of genital chlamydial infections, compared with urine samples, has not been well studied and little data exist to document women's preferences for the different types of self-collected samples. We undertook this study to assess the acceptability of SAS as screening specimens for the detection of chlamydial infection in nonhealthcare-seeking female soldiers who were invited to provide both SAS and urine specimens at a single visit. We also evaluated preference for SAS, compared with urine, and the sensitivity and specificity of SAS using urine as the standard.
Materials and Methods
Study Population
Female Army recruits who entered basic training at Fort Jackson, South Carolina, during March through August 1999 were invited to participate in our study. The participants were given a study and educational briefing about genital chlamydial infection and its sequelae and were instructed about collection of both samples. The self-administrated vaginal swabs instruction material included a diagram of the female genital anatomy, described steps of removing a Dacron swab from the swab packet, described how to self-collect a vaginal swab specimen, and indicated steps for putting the swab into the test tube. After signing a consent form, participants were asked to obtain a 20-mL first-void urine (FVU) specimen in a container provided by the study team, then to self-collect a vaginal sample using a Dacron swab (Baxter Scientific, McGaw Park, IL) and place it into the LCR transport tube containing transport buffer. Then participants were instructed to break off the shaft of the swab leaving the swab in the tube and replace the cap. After specimen collection, volunteers were asked to complete a questionnaire that addressed basic demographic information, sexual risk behaviors, history of sexually transmitted diseases, and questions on sample preference and comfort with use. The preference and comfort domains were assessed by questions relating to ease of collection, comfort in collection, pain during collection, handling of specimens, preference in collection method by setting (clinic, home, and field), and intention to use.
This study was approved by the institutional review boards of The Johns Hopkins University, the U.S. Army Medical Research and Material Command, Fort Detrick, Maryland, and Fort Jackson (supported by the Eisenhower Army Medical Center, Fort Gordon, Georgia). All diagnostic specimens, consent forms, and questionnaires were shipped to The Johns Hopkins University International Chlamydia Laboratory. FVU specimens and SAS samples were kept at 4°C until processing within 48 to 72 hours.
Laboratory Procedures and Treatment
FVU and SAS specimens were processed and tested for chlamydia by LCR (Abbott Laboratories, Abbott Park, IL) according to the manufacturer's directions. FVU samples (1 mL) were centrifuged and the pellet tested in the assay. SASs were handled according to the manufacturer's instructions for cervical specimens. Recruits whose specimens tested positive on any assay were promptly informed and requested to attend the installation Troop Medical Clinic, where they were treated with a single, 1-g oral dose of azithromycin and received an evaluation for other sexually transmitted diseases. They were also referred for counseling and encouraged to notify their sexual partners.
Statistical Analysis
Univariate analyses (chi-squared tests) were used to investigate associations of demographics, sexual risk factors, and LCR results with questionnaire data. For these analyses, age was categorized into >25 years and ≤25 years dichotomous variables because of previous findings regarding age-specific chlamydial infection prevalences in this population. 9 P values of <0.05 were considered significant. All analyses were performed using Statistical Analysis Software version 8.2 (SAS Institute Inc, Cary, NC) or Stata 6.0 (Stata Corp, College Station, TX).
Relative sensitivity and specificity of the LCR results on SAS were calculated using the LCR results on urine specimens as the standard, because this specimen has been cleared by the U.S. Food and Drug Administration for the LCR assay. Relative sensitivity and specificity on urine and SAS were also calculated using any positive LCR result as an analytical “true positive.”
Results
Demographic Characteristics and Risk Factors for Sexually Transmitted Infections
Thirty-one percent (1403 of 4496) of female Army recruits, who had volunteered to participate in a urine prevalence study, also volunteered to participate in the SAS study and completed questionnaires (Table 1 ). All but 21 provided both SAS and urine specimens (15 participants provided urine specimens only and 6 provided SAS only). Thus, there were 1382 matched urine and SAS samples. The mean age of participants was 20.3 ± 3.6 years (mean ± standard deviation; range, 17–36 y). White (48.3%) was the most commonly reported race, followed by black (35.7%) and other races (13.1%). Forty (2.9%) individuals did not report their race. Almost half of the study subjects identified their home of record as being in the South (656, 46.8%), followed by Northeast (268, 19.1%), Midwest (249, 17.7%), West (208, 14.8%), and the Territories (22, 1.6%). Most (1188, 84.7%) participants reported ever having had vaginal sex and 1166 (83.1%) women reported that they had practiced sexual risk behavior in the previous 90 days (more than one sexual partner, new sexual partner, or had had sex without using a condom). Only 2.1% (30 of 1403) of the women studied reported ever having been diagnosed with a sexually transmitted disease and 0.5% (7 of 1403) reported having been diagnosed previously with a genital chlamydial infection.
TABLE 1: Demographic Profile of 1403 Female Army Recruit Study Participants at Fort Jackson, SC (1999)
Prevalence of Infection and Sensitivity and Specificity of LCR on SAS
Among the 1403 study participants, 166 (11.8%) were infected with chlamydia by LCR testing of either their FVU or SAS. There were 3.3% (7 of 208) of the women who reported not having had vaginal sex who were chlamydia-positive. All but one (6 of 7) were positive in both types of specimens. Therefore, responses regarding ever having had vaginal sex were excluded from further analyses. The 21 females without matched FVU and SAS pairs were also excluded from further analyses. The 1382 matched sample pairs contained 120 pairs that were positive from both urine and SAS and 1217 pairs that were negative on both specimens. There were 17 that were FVU-negative/SAS-positive and 28 were FVU-positive/SAS-negative. Using the test result on the urine specimen as the comparison standard for the 1382 paired specimens, relative sensitivity for SAS specimens was 81.1% (95% CI, 73.8-87.0%) and relative specificity was 98.6% (95% CI, 97.8-99.2%). When any positive result on a FVU or SAS was considered a true analytical positive, the relative sensitivity for FVU and SAS were 89.7% (95% CI, 84.0-93.9%) and 87.6% (95% CI, 80.9-92.6%), respectively, and the relative specificity was 100.0% for both.
Collection Method Preference and Comfort Issues
Overall, 90.8% of respondents (1255 of 1382) indicated that they felt comfortable collecting a FVU specimen, whereas 69.6% (962 of 1382) felt comfortable collecting SAS (P <0.001). When queried about ease of use, 60.4% (834 of 1382) reported that urine was the easier method, 33.2% chose SAS, and 6.4% did not have a preference (P <0.001). Either specimen collection type received high acceptability at home and in the field (FVU at home: 90.9%, in the field: 79.4%; SAS at home: 82.9%, in the field: 68.8%). When given a choice of collection method (FVU or SAS), collecting a FVU specimen was the preferred method in the clinic (56.4% vs. 32.9%, P <0.001), the home (52.0% vs. 39.1%, P <0.001), and the field (50.4% vs. 36.5%, P <0.001).
The reasons given for preferring the collection of urine over SAS were varied (Table 2 ). Some women reported feeling uncomfortable collecting (19.0%) or carrying (10.8%) FVU samples. Pain on collecting a urine specimen was uncommon (0.1%). Some stated that collecting a SAS was more uncomfortable than collecting FVU (26.3%; vs. urine:P <0.001) or more painful (2.2%; vs. urine:P <0.001). Fewer women reported feeling uncomfortable about carrying the SAS compared with carrying a FVU specimen (3.8%; vs. FVU:P <0.001). Chlamydia test results were not associated with specimen preferences or comfort level.
TABLE 2: Comfort Issues for First-Void Urine (FVU) and Self-administrated Vaginal Swab Collection Methods Reported by 1382 Female Army Recruits at Fort Jackson, SC (1999)
Multivariate Analyses
After adjusting for other covariates, white Army recruits were more likely than black recruits to report that SAS was the easier collection method (Table 3 ). White soldiers were more likely than blacks to choose SAS as the easier collection method and the collection method of choice for the diagnosis of chlamydial infection in the field as well. Participants of “other races” were more likely to state that they were uncomfortable in collecting and carrying SAS (Table 3 ).
TABLE 3: Multivariate Logistic Regression Analyses of Variables Associated With Preference and Comfort With Use of Self-administered Vaginal Swabs (SAS) in 1382 Female Army Recruits in Fort Jackson, SC (1999)
Volunteers who stated any sexual risk behaviors (having more than one sexual partner, new sexual partners, or sex without a condom) in the past 90 days had more favorable ratings for the use of SAS (Table 3 ). Having reported any sexual risk behaviors in the past 90 days was associated with the choice of SAS as the collection method in the clinic and at home (Table 3 ).
In another model controlling for age, region, and risk behaviors, “other races” indicated that they felt pain in collecting SAS as compared with black participants (felt pain: OR, 3.68; 95% CI, 1.21-11.22). When findings were adjusted for region, race, and risk behaviors, women who were ≤25 years were less likely to report that they would collect FVU in the field compared with those who were >25 years (OR, 0.54; 95% CI, 0.29-1.00). There were no significant differences by age with regard to other preferences, acceptability, and comfortableness questions (data not shown).
Discussion
This study compared the preference, comfort level, sensitivity, and specificity of 2 specimen collection methods in young female military recruits. When queried in conjunction with the use of FVU and SAS sampling, these women preferred the collection of FVU specimens but viewed SAS as an acceptable alternative. We found that the use of SAS did not diminish the sensitivity and specificity of the LCR assay for detection of chlamydia when compared with FVU, and we demonstrated either SAS or FVU specimen type could be used to detect chlamydia. Army females who were white or who reported having practiced sexual risk behaviors in the past 90 days were more comfortable using SAS, whereas those of other races or reporting no sexual risk behaviors preferred to collect FVU samples.
Invasive specimen collection methods and the requirement for active involvement by healthcare providers have been barriers to expansion of effective screening programs for sexually transmitted infections. Since the mid-1990s, urine, a noninvasive collection method that eliminates the discomfort and embarrassment often associated with clinician-collected genital samples, has been proven to be highly acceptable in screening programs for genital chlamydial infections in diverse settings. 32 Neisseria gonorrhoeae , human papillomavirus, and Trichomonas vaginalis . 6,25,26
We anticipated a stronger preference among female recruits for urine rather than SAS because public health professionals have promoted urine for several years. For most study participants, SAS was probably a novel collection method that was introduced to them for the first time in this study. Approximately 70% of participants reported that they were comfortable collecting SAS, indicating that SAS made a relatively good impression and suggesting that this novel method might have the potential to improve in acceptability with further promotion. A study by Verhoeven and colleagues showed that 77% of subjects who were provided a self-collection package returned a sample, 33
Women might feel that SAS is not as reliable as other methods for the diagnosis of chlamydia. 33 26 26,34
Females with sexual risk behaviors reported being comfortable in collecting the SAS and that they would be likely to use SAS in different settings. This is an important finding because sexually active women reporting high-risk sexual behaviors are at significant risk for chlamydial infections. Women of races other than white reported less preference for the SAS and felt more uncomfortable using the SAS. After obtaining a better understanding of different cultural backgrounds and biases, more detailed and specific “how-to-collect SAS” instructional materials might be helpful in some subgroups of women.
Studies on young military women have demonstrated that they are at high risk for chlamydial infections. 9,35 C. trachomatis screening program has the potential to benefit military women, especially when they are in the field. The self-administrated vaginal swab might be an alternative specimen collection method for implementing sexually transmitted infection screening programs in unique populations in nontraditional settings or remote areas where urine specimens might not be feasible. 30
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