SINCE THE MID-1980s, there have been concurrent increases in the incidence of both tuberculosis (TB) and syphilis.1–4 Human immunodeficiency virus (HIV) has been linked epidemiologically to both diseases. The depressed immune function in people with HIV increases the vulnerability of patients to tuberculosis infection and reactivation.5 Sexually transmitted diseases (STDs), especially syphilis and other genital ulcer diseases, are significant risk factors for the acquisition of HIV.6–8 These clinical relationships underscore the epidemiologic studies that indicate that tuberculosis, syphilis, and HIV are disproportionately found within the same population: heterosexual, young persons living in low socioeconomic environments.2,9,10 Medical anthropologists have posited that environmental factors underscore the clinical relations of these diseases. These conditions are characterized as part of a broader inner-city health crisis, one in which endemic and epidemic conditions are influenced by political, economic, and social factors.11
Traditional public health approaches to TB and syphilis have resulted in the development of categoric (i.e., disease-specific) clinical facilities. If there is true overlap between the TB and STD clinic populations, this categoric approach may result in inefficient use of scarce resources and may indicate a need to more closely integrate these clinical activities.
We conducted a retrospective study to determine the coinfection rate of syphilis and other STDs and the use of STD clinic services in patients seen for TB evaluation at the Baltimore City Tuberculosis Clinic, Baltimore, Maryland.
Files were obtained from the TB clinic on 764 patients seen consecutively between January 2, 1992, and January 11, 1993. Patients are referred to the TB clinic for evaluation from area hospitals (76.9%), outpatient clinics (0.96%), private physicians (10.6%), self-referral (0.96%), the Department of Corrections (0.96%), and direct contacts of persons with active TB (9.6%). Not all patients initially evaluated at the TB clinic will be diagnosed ultimately with active TB; only a portion will require medical therapy and follow-up. Therefore, for the purpose of this study, patients from the TB clinic will be defined as all those initially presenting to the TB clinic for evaluation.
Charts were abstracted by one of the authors (MP) for patients 15 to 45 years of age, which is the age group at highest risk for STD. Data elements included name, social security number, date of birth, gender, race, purified protein derivative (PPD) result, and TB and HIV status. Racial classification was based on self-report. Positive PPD was defined as induration 10 mm at 48 to 72 hours. Active Mycobacterium tuberculosis infection was defined as a positive sputum smear of acid-fast bacilli or positive culture. Syphilis was defined using standard clinical and laboratory criteria.12
Records from the 764 TB clinic patients were matched with those from the Baltimore City Health Department Syphilis Registry by name, social security number, date of birth, and address. Information was obtained on syphilis status, stage of disease, reactive plasma reagin titer and fluorescent treponemal antibody status, number of previous syphilis infections, date and location of diagnosis, and HIV status.
These 764 records from the TB clinic also were matched with those from the computerized medical data records of the Baltimore City Sexually Transmitted Disease Clinics by name, date of birth, and social security number. Clinic visits and registration information at the STD clinics were fully computerized in early 1991. Information was obtained on location of visit, syphilis status, and HIV status by chart review.
Data on TB and STD patients were entered onto standardized forms. Data analysis was performed using Epi-Info (CDC, Atlanta, GA) and PC-SAS 6.03 (SAS Institute, Cary, NC). Confidential data abstraction was performed under Health Department guidelines and also was approved by the Johns Hopkins University Joint Committee on Clinical Investigation.
Of the TB clinic attendees, 35.5% were women and 64.5% were men. The ethnic composition was 79.0% blacks, 15.3% whites, and 5.8% people from other ethnic backgrounds. Although this patient population reflected the composition of the surrounding neighborhood, the clinic also received referrals from private and public clinics in Baltimore City. Four hundred ninety-one patients (64.3%) had a positive PPD or active TB; of these 491 persons, 44 (9.0%) had an STD registry record indicating a history of syphilis. Of the 273 persons without TB or a positive PPD, 24 (8.8%) had a disease registry record of syphilis. There was no significant difference in syphilis history among clinic patients when stratified by TB status (odds ratio for history of syphilis = 1.02; 95% Cornfield confidence limit, 0.59–1.79).
Of the TB clinic patients with documented syphilis, the average age was 38.4 years; 13 (19.1%) of 68 had been diagnosed within 1 year of the TB clinic visit, 19 (27.9%) of 68 had between 1 and 5 years of the clinic visit, and 12 (17.6%) of 68 had within 5 and 10 years of a clinic visit. Thus, a total of 44 (64.7%) of 68 of the patients visiting the TB clinic had been diagnosed with syphilis within 10 years of their initial clinic visit.
Of the 491 persons with diagnosed TB or a positive PPD, 70 (14.3%) had a history of at least 1 visit to a Baltimore STD clinic compared to 34 (12.5%) of the 273 without diagnosed TB (odds ratio = 1.17; 95% Cornfield confidence limit, 0.73–1.86) (Table 1). The total number of patients having had at least 1 visit to a Baltimore STD clinic was 104 (13.6%) of 764; 30 (28.8%) were women and 74 (71.2%) were men. Ethnicity classification data were available for 94 patients: 90 (95.7%) were blacks, 3 (3.2%) were whites, and 1 (1.1%) was from another ethnic background. Because the STD clinics were computerized in 1991, nearly all these visits occurred within a year's time of the TB clinic visit.
For the 694 persons where racial classification was available, 90 (16.5%) of 547 of blacks, 3 (2.9%) of 105 of whites, and 1 (2.4%) of 41 of persons from other ethnic backgrounds had visited a Baltimore STD clinic (odds ratio = 7.04). Similarly, 12.1% of blacks, 5.7% of whites, and 2.5% of persons belonging to other ethnic groups had a history of syphilis infection.
Our data indicate substantial cross-utilization of the TB and STD clinics. For patients referred to the TB clinic, 9.0% had a history of syphilis, higher among blacks. Among these patients, syphilis status or history of STD clinic visit did not vary whether they had active TB or solely a positive tuberculin skin test.
Of all patients seen at the TB clinic, 13.6% also received medical care from a Baltimore STD clinic, usually within the past year. When stratified by ethnicity, black TB clinic patients are more likely to be Baltimore STD clinic patients than are whites or members of other ethnic groups. Of all blacks seen at the TB clinic, 16.5% had at least one visit to a city STD clinic as compared to 2.9% of whites and 2.4% of other ethnic groups.
The rate of syphilis is substantially higher than that of the general population, indicating that perhaps the risk of syphilis is substantially higher in all attendees at the TB clinic. These findings may not be specific to the TB clinic population. For example, a recent study from the Johns Hopkins Hospital Medicine ward service, which serves the population predominantly of inner-city East Baltimore, found that 52 (11.0%) of 463 inpatients had positive syphilis serologies (M. Glesby, personal communication, 1995).
Baltimore has a much lower incidence rate of TB than do comparable cities, largely due to its use of directly observed therapy as the strategy for TB control.9 Because this aggressive TB treatment regimen limits the generalizability of our data, it would be important to confirm our findings with studies in other urban areas where TB prevalence is comparable to the national average.
The higher prevalence of blacks receiving care from public STD clinics can be interpreted in two ways. Most blacks seen at the TB clinic are from the surrounding neighborhoods of East Baltimore, which also have the highest STD rates. Alternatively, the higher prevalence of blacks receiving care from public STD clinics may reflect their access to health care.10 Urban minorities, especially those individuals at greatest risk for STDs and TB such as injecting drug users and other substance abusers, adolescents, and those who are marginally employed, are more likely to live below the poverty line and rely on government-funded public health clinics for their medical care.10 We would posit that blacks are more likely to attend public STD clinics, whereas nonblacks are more likely to attend private clinics to receive treatment for STDs. Yet, both blacks and nonblacks are equally likely to attend public TB clinics because the TB clinic is the referral center for both the public and private sector.
However, regardless of the reason for the higher prevalence of STD clinic visits among blacks, the data have important public health implications. Tuberculosis clinics in urban environments often serve patient populations that coincide with those at public STD clinics. Because of this overlap, cross-screening for syphilis and TB at urban clinics could be an important mechanism of identifying new cases of disease. Because this retrospective study used a history of syphilis as a proxy for incidence of treponemal infection, we can only hypothesize about the utility of cross-screening in detecting new cases of disease. Nonetheless, the data indicate that new cases of syphilis are likely to be found.
To create the complete picture of population overlap, it would be important to know what percentage of the total Baltimore STD clinic population also had been screened at the TB clinic. Unfortunately, the Baltimore STD clinic database does not include information on TB clinic use.
Cross-screening for syphilis and TB could be a cost-effective method to help control the resurgence of both diseases. The Centers for Disease Control has recommended cross-screening for syphilis and HIV in newly diagnosed people; a similar policy for syphilis and TB could be implemented.2 It also has been suggested that more routine syphilis screening and effective targeted educational campaigns in inner-city minority groups be conducted.13 Studies of injecting drug using populations and their medical needs indicate that HIV-related illness (including TB) and STDs (primarily syphilis and gonorrhea) are among the major health concerns.14–16 Our STD clinics, on a limited basis, already have integrated family planning and STD services.17
Our data suggest that STD and TB control services frequently are used by similar populations. Therefore, integration of these services probably may result in more efficient use of resources and better compliance.
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