Impact of sex-based differences in testing practices on C hlamydia trachomatis and Neisseria gonorrhoeae infection rates in military service members

Abstract

Background

Chlamydia trachomatis and Neisseria gonorrhoeae infections impose a significant burden to the military. In previous studies, women service members had higher rates of both these infections as compared to men for unclear reasons. This study evaluated if sex-based differences in infection rates for chlamydia and gonorrhea were due to sex-based differences in testing practices.

Methods

A retrospective chart review was conducted on military service members who underwent testing for chlamydia and gonorrhea at Joint Base San Antonio between June 1, 2023 and September 31, 2023. The local electronic health record database was queried to determine patient demographics, clinical setting, indications for testing, and positivity rates.

Results

A total of 1620 (43%) patients were included for analysis. The cohort was predominantly women (67.5%) and enlisted (84.2%) with a median age of 27 years [IQR: 23–32]. Men were more likely to be tested for patient driven factors, such as symptoms (41.2%) or patient request (24.5%). Women were most frequently tested due to clinical algorithm (53.0%). Men were more likely to test positive for both chlamydia (8.7% vs 3.9%, p = <0.001) and gonorrhea (2.8% vs 0.4%, p = <0.001).

Conclusions

Although women were more frequently tested for chlamydia and gonorrhea infections, men had significantly higher positivity rates, with more patient-driven indications for testing. The result of this study implies that sex-based testing practice differences in our study population might partially account for the higher rates in men. Importantly, it supports the need for future studies to evaluate the effectiveness of screening men in military settings.

Keywords

Chlamydia trachomatis Neisseria gonorrhoeae military sexually transmitted infections

Introduction

Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC) are the two most common bacterial causes of sexually transmitted infections (STIs) in the United States and cause significant morbidity.^1,2 The United States Preventive Services Task Force (USPSTF) recommends screening for CT and GC in all sexually active women 24 years or younger and in women 25 years or older who are at increased risk for infection.³ The intent of the recommendations is to decrease the risk of pelvic inflammatory disease (PID) and its associated complications, such as ectopic pregnancy, infertility, and chronic pelvic pain. There are no similar recommendations for men even though infection may lead to urethritis and epididymitis.⁴ With the vast majority of CT and GC infections being asymptomatic, it is believed that a minority of cases are detected with current screening and testing strategies.⁵

STIs impose a significant burden to the United States military, due to its young, sexually active population.⁶ While only 17.94% of the United States military are women,⁷ they had 3–5 times the reported incidence rate of both these infections as compared to men for unclear reasons.⁸ Despite this difference in infection rates, there is limited data on number of individuals being tested for CT and GC and the positivity of those tested. In previous studies that universally screened men basic trainees, the rates of CT were the same as universally screened women at the same time.⁹ We hypothesize that sex-based differences in infection rates for CT and GC are due to sex-based differences in testing practices.

Materials and methods

We performed a retrospective cross-sectional study evaluating CT and GC testing at Joint Base San Antonio (JBSA) between June 1, 2023, and August 31, 2023. Joint Base San Antonio is a large military base and is the sole location for entry into the United States Air Force (USAF) or United States Space Force (USSF). JBSA includes service members from every military branch, all of whom can receive care in outpatient or inpatient settings. Service members are universally insured with no co-pay for medical services. Per current military regulations, all service members receive a human immunodeficiency virus (HIV) screening test every 2 years. Women 24 years of age and younger are instructed to undergo annual CT and GC screening to prevent long term complications as per the United States Preventive Services Task Force (USPSTF) recommendations.³ Additionally, all women entering USAF or USSF basic training receive screening for CT and GC at entry. This screening is not offered to men entering USAF or USSF basic training. Men and women 25 years and older have no dedicated screening process, except those who self-identify as high risk for STIs or are pregnant as per the Centers for Disease Control guidelines.¹

This study evaluated all military service members who tested for CT and GC during the study period. Nucleic acid amplification testing was performed using the Aptima Combo two assay (Hologic, Marlborough, MA). For patients with testing, charts were manually reviewed to determine demographic information, ordering clinic, indications for testing, and positivity rates. We excluded all women USAF and USSF Basic Military Trainees who were universally screened on entry during the study period, as their outcomes were previously described.¹⁰

We stratified service members by demographics that were documented in their medical record. We identified those who were symptomatic at the time of testing. For those who were asymptomatic, the reason for testing was further elucidated. Testing that was performed due to demographics, previous history of STI, or due to medications a person was taking (such as birth control or pre-exposure prophylaxis for HIV) were considered tests by clinical algorithm. Alternatively, when a patient requested testing due to exposure or risk factors was determined to be a patient requested test. When data was missing for indication, the test was labeled as unknown. We described testing characteristics among individuals who tested and among those who tested positive, stratified by sex.

Continuous variables were compared by Mann-Whitney-U test. Chi-squared test and Fisher’s Exact Test were used for comparisons between categorical variables. A p = value of 0.05 was predetermined to be significant. This protocol was reviewed by the San Antonio Institutional Review Board determined to be exempt (protocol number: 24–20521), and consent was not required from the patients.

Results

A total of 3768 service members underwent testing for CT and GC during the study period. Of these, 2148 women Basic Trainees who underwent mandatory entry screening and were subsequently excluded, which left 1620 (43%) patients for analysis. The cohort of service members was predominantly women (67.5%) and enlisted (84.2%) with a median age of 27 [IQR: 23–32]. Most service members were in the USAF (51.0%). There were several significant differences between men and women who were tested for CT and GC (Table 1). Women with testing were younger than men (median 25 [IQR 22–31] vs 29 [24–34], p < 0.001) and less likely to be receiving HIV pre-exposure prophylaxis/PrEP (0.2% vs 18%) or be living with HIV (0% vs 6.6%). At the four most junior enlisted ranks (E1-E4), there were more women tested than men (56.6% vs 41.9%). One hundred and ninety-five (17.8%) women service members were pregnant at the time they were tested. The most common clinicians to order tests on men were primary care providers (45.0%), while most women were tested by a women’s health provider (60.9%). Infectious Diseases providers, which provides the majority of PrEP and HIV care on base, tested 22.4% of all men in this cohort. Thirty-four men were tested by a women’s health provider as part of infertility evaluation or treatment. Only a minority of men and women tested were symptomatic, and there was a similar percentage tested due to symptoms among both sexes (41.2% vs 39.1%, p = 0.416). Asymptomatic men were more likely to request testing than asymptomatic women (24.5% vs 7.2 %, p = <0.001). Alternatively, women were most frequently tested due to clinical algorithm (53.0% vs 32.8%, p = <0.001). Tested men were more likely to have a positive result than women for both CT (8.7% vs 3.9%, p = <0.001) and GC (2.8% vs 0.4%, p = <0.001).

Table 1.

Testing characteristics of 1620 service members tested for chlamydia and gonorrhea during study period by sex.

	Men (n = 527)	Women (n = 1093)	p-value
Median age (Interquartile range)	29 (24–34)	25 (22–31)	<0.0001
Race
White	309 (58.6%)	598 (54.7%)	0.0137
Black	128 (24.3%)	315 (28.8%)
Asian	8 (1.5%)	46 (4.2%)
Native Hawaiian	58 (11.1%)	85 (7.8%)
American Indian	6 (1.1%)	9 (0.8%)
Other	15 (2.8%)	33 (3.0%)
Unknown	3 (0.6%)	7 (0.7%)
Ethnicity
Hispanic or latino	121 (22.9%)	280 (25.6%)	0.0826
Not Hispanic or latino	392 (74.4%)	799 (73.1%)
Unknown	14 (2.7%)	14 (1.3%)
Pregnant	-- (N/A)	195 (17.8%)	-- (N/A)
Living with human immunodeficiency virus (HIV)	35 (6.6%)	0 (0.0%)	<0.0001
Receiving HIV pre-exposure prophylaxis (PrEP)	96 (18.2%)	2 (0.2%)	<0.0001
Clinic
Emergency department	117 (22.2%)	102 (9.3%)	<0.0001
Primary care	237 (45.0%)	317 (29.0%)
Women’s health	34 (6.5%)	665 (60.9%)
Urology	6 (1.1%)	0 (0.0%)
Infectious diseases	118 (22.4%)	1 (0.1%)
Public health/other	15 (2.8%)	8 (0.7%)
Indication for testing
Symptoms	217 (41.2%)	427 (39.1%)	0.416
Patient request	129 (24.5%)	79 (7.2%)	<0.0001
Provider/clinical algorithm	173 (32.8%)	579 (53.0%)	<0.0001
Unknown	8 (1.5%)	8 (0.7%)	0.134
Branch
Army	173 (32.8%)	348 (31.8%)	0.0449
Navy	78 (14.8%)	177 (16.2%)
Air force	270 (51.2%)	557 (50.9%)
Space force	0 (0.0%)	2 (0.2%)
Marine corps	5 (1.0%)	3 (0.3%)
Coast guard	1 (0.2%)	3 (0.3%)
Public health service	0 (0.0%)	3 (0.3%)
Rank⁺
E1-E4	221 (41.9%)	619 (56.6%)	0.0001
E5-E6	166 (31.5%)	257 (23.5%)
E7-E9	52 (9.9%)	48 (4.4%)
CW1-CW5	3 (0.6%)	3 (0.3%)
O1-O3	53 (10.0%)	132 (12.1%)
O4-O6	32 (6.1%)	34 (3.1%)
Chlamydia positive	46 (8.7%)	43 (3.9%)	<0.0001
Gonorrhea positive	15 (2.8%)	4 (0.4%)	<0.0001

+: Enlisted ranks abbreviated as E#, chief warrant officer ranks abbreviated as CW#, officer ranks abbreviated as O#.

Evaluating the 103 (6.4%) individuals who tested positive for CT or GC or both (Table 2), men tended to be older (median 27 [IQR 22–32] vs 23 [IQR 19–23], p = <0.001). Four (8.7%) of the women with positive tests were pregnant and had a positivity rate of 2.1%. Men living with HIV or receiving HIV PrEP accounted for 31.6% of all positive tests in men. Half of all positive tests for women were ordered by a women’s health provider. Only a minority of men who tested positive had symptoms while most women were symptomatic (43.9% vs 58.7%).

Table 2.

Demographics of 103 individuals testing positive for chlamydia, gonorrhea or both.

	Men (n = 57)	Women (n = 46)	p-value
Median age (Interquartile range)	27 (22–32)	23 (19–23)	<0.0001
Race
White	33 (57.9%)	23 (50.0%)	0.9183
Black	16 (28.0%)	12 (26.0%)
Asian	3 (5.3%)	4 (8.7%)
Native Hawaiian	2 (3.5%)	4 (8.7%)
American Indian	1 (1.8%)	1 (2.2%)
Other	1 (1.8%)	1 (2.2%)
Unknown	1 (1.8%)	1 (2.2%)
Ethnicity
Hispanic or latino	13 (22.8%)	13 (28.3%)	0.5615
Not Hispanic or latino	43 (75.4%)	33 (71.7%)
Unknown	1 (1.8%)	0 (0.0%)
Pregnant	-- (N/A)	4 (8.7%)	-- (N/A)
Living with HIV	7 (12.3%)	0 (0.0%)	0.0002
Receiving PrEP	11 (19.3%)	0 (0.0%)	0.0002
Clinic
Emergency department	14 (24.5%)	7 (15.2%)	<0.0001
Primary care	23 (40.3%)	15 (32.6%)
Women’s health	1 (1.8%)	23 (50.0%)
Urology	0 (0.0%)	0 (0.0%)
Infectious diseases	18 (31.6%)	0 (0.0%)
Public health	1 (1.8%)	0 (0.0%)
Indication for testing
Symptoms	25 (43.9%)	27 (58.7%)	0.1577
Patient request	12 (21.0%)	8 (17.4%)
Provider/clinical algorithm	19 (33.3%)	11 (23.9%)
Unknown	1 (1.8%)	0 (0.0%)
Branch
Army	22 (38.6%)	7 (15.2%)	0.2895
Navy	13 (22.8%)	12 (26.1%)
Air force	20 (35.1%)	26 (56.5)
Space force	0 (0.0%)	0 (0.0%)
Marine corps	2 (3.5%)	1 (2.2%)
Coast guard	0 (0.0%)	0 (0.0%)
Public health service	0 (0.0%)	0 (0.0%)
Rank⁺
E1-E4	30 (52.6%)	37 (80.4%)	0.0131
E5-E6	16 (28.0%)	9 (19.6%)
E7-E9	3 (5.3%)	0 (0.0%)
CW1-CW5	0 (0.0%)	0 (0.0%)
O1-O3	3 (5.3%)	0 (0.0%)
O4-O6	5 (8.8%)	0 (0.0%)

+: Enlisted ranks abbreviated as E#, chief warrant officer ranks abbreviated as CW#, officer ranks abbreviated as O#.

The positivity rate differed by both clinic and sex with the highest positivity rate seen in infectious disease clinic ordered tests (15.3%) (Table 3). Positivity rates were significantly greater in men tested in primary care compared to women tested in primary care (9.7% vs 4.7%, p = 0.021), but there was no significant difference in positivity for those tested in the emergency department (12.0% vs 6.9%, p = 0.750). The lowest positivity rate was seen in women tested by women’s health (3.5%).

Table 3.

Positivity rates by clinical setting and sex.

	Men	Women	p-value
Emergency department	14/177 (12.0%)	7/102 (6.9%)	0.750
Primary care	23/237 (9.7%)	15/317 (4.7%)	0.021
Women’s health	-- (N/A)	23/665 (3.5%)	-- (N/A)
Infectious diseases	18/118 (15.3%)	-- (N/A)	-- (N/A)

Discussion

This study evaluated CT and GC testing practices amongst military service members at a large United States military base. Despite the predominance of men in the military, the vast majority of testing occurred in women and there are clear differences in testing practices by sex. Women were more likely to be tested by clinical algorithm, while men were more likely to request testing. In this cohort, men had twice the positivity for CT and seven times the positivity for GC. Men tested by infectious disease clinic had the highest positivity rate, while women had the highest positivity rate when tested by emergency medicine.

More than 70% of urogenital chlamydial infections in women, and more than 80% of urogenital infections in men are asymptomatic.^5,11,12 Between 86.4% and 92.6% of urogenital infections among women with gonorrhea may be asymptomatic while 55.7%–86.8% of urogenital infections in men are thought to be asymptomatic.^5,11,12 Most persons with CT infection are not aware of their infection because they do not have symptoms that would prompt them to seek medical care.¹³ Despite more screening in women, we were surprised to find twice as many women with symptoms were tested as compared to men in our study, despite only accounting for roughly a sixth of the population. This brings into question differences by sex in presenting for medical care for possible STIs or alternatively provider testing differences in ordering STI tests in symptomatic patients by sex.

Military recruits and service member have been shown to have higher rates of STIs than the national average with previous studies attributing this difference to young sexually active adult populations in cohort environments, inconsistent condom use, multiple sexual partners, and binge drinking.^14–20 Additionally, diagnoses of STIs are stigmatized partly due to their potential impacts on military careers, the fear of rejection, shame, and embarrassment.²¹ Previous studies have shown that military service members have an incorrect perception of their HIV risk, which implies that they they also have incorrect perception of their STI risk.²² Some of these risk factors might be different between sexes.²³ As contact tracing has many limitations to finding all partners of patients that test positive for an STI, the identifications of high risk sexual networks is difficult and challenges designing a STI screening protocol for the military.²⁴ This is especially pertinant as positive CT or GC test results provide an opportunity for additional counseling and consideration of PrEP and DoxyPEP, which can decrease burden of STIs throughout a community.²⁵

A surprising finding of this study was that a higher proportion of men tested for GC or CT requested their testing. This is at least partially explained by the limited screening programs that exist for men outside of patients living with HIV or receiving PrEP, while women who are pregnant or under 25 are screened. It is also notable that despite more men asking for testing, women are still approximately twice as likely to request testing as men if the population on this base matches the population of the military as a whole. With the extensive preventative medicine program in the military, this may account for the high presentation rates for patient requested testing in asymptomatic women.

Our study has several limitations as a single center cross-sectional study evaluating the ordering of CT and GC tests. We did not evaluate other sexually transmitted infections, such as syphilis, which are also of clinical concern and on the rise. We were only able to capture tests that were performed on military bases and could not capture testing of military service members that occurred in civilian facilties or sexual health clinics and it is unknown how frequent different sexes utilize services in the community. The short time period, 3 months, of this study may also limit its generalizability. While this study evaluted military service members in a base with a large medical infrastructure, it is unclear how generalizable it would be to a military base with a smaller medical footprint.

In conclusion, the results of this study demonstrated significant differences in CT and GC testing practices by sex in a large military population. Despite the predominance of men in the military, the vast majority of testing occurred in women. Women were more likely to be tested by clinical algorithm, while men were more likely to request testing. In this cohort, men had twice the positivity for CT result and 7 times the positivity for GC. These findings provide a first step in understanding current STI testing practives to provide context to STI positivity rates and allow for the design of future educational and pharmacologic interventions for asymptomatic men and studies to evaluate the effectivenes of screening men to improve outcomes and reduce burden of CT and GC in military settings.

Footnotes

Ethical considerations

This protocol was reviewed by the San Antonio Institutional Review Board determined to be exempt (protocol number: 24–20521) per the United States Department of Health and Human Services Revised Common Rule.

Consent to participate

The requirement for informed consent was waived by the San Antonio Institutional Review Board.

Author contributions

Conceptualization: DAR, JEM, Methodology: DAR, JEM, Formal Analysis: JKA, Investigation: DAR, MAA, JEM, Writing Original Draft: DAR, Writing -Review and Editing: DAR, JKA, MAA, JEM

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Disclaimer

The views expressed herein are those of the author(s) and do not necessarily reflect the official policy or position of the Defense Health Agency, Brooke Army Medical Center, the Department of Defense, nor any agencies under the U.S. Government.

ORCID iD

Joseph E. Marcus

Data Availability Statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.*

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