Patients at Sexually Transmitted Disease Clinics
Because STD clinics provide comprehensive HIV prevalence data for MSM and
high-risk heterosexual patients who attend these clinics, they are important
sites for evaluating HIV prevention programs and for monitoring emerging
patterns and trends in the HIV epidemic. These STD clinics, most of which are
supported by state or local health departments, generally provide services to
low-income patients in urban areas. They serve large numbers of persons at
increased risk for HIV infection because the patients typically have engaged in
unprotected sex or other high-risk behaviors, such as sex with multiple
partners. Persons at the greatest risk of acquiring HIV infection sexually are
also those at risk of acquiring other STDs; thus, surveys in STD clinics provide
useful information on the sexual transmission of the HIV epidemic among
high-risk persons.
Depending on the number of patients visiting a particular clinic, the survey
period for data collection ranged from 6 weeks to 1 year. The survey included
serum specimens from patients who had not visited the clinic either during the
preceding 3 months (applies to data collected from 1993–1996) or since the
current survey period (beginning in 1997) and who had blood drawn for routine
clinical purposes other than HIV testing, usually for serologic syphilis
testing. Through 1996, specimens were excluded from patients who attended the
clinics for (1) follow-up visits for diseases that had been diagnosed during the
current survey period, (2) HIV testing and counseling only, or (3) for treatment
of HIV infection. Beginning in 1997, the eligibility criteria were modified to
include specimens from all patients who had not previously attended the clinic
during the current survey period and for whom a routine blood test was ordered.
Specimens from clients who attended the clinics only for HIV testing were
included if blood had been drawn at that visit for routine purposes other than
for HIV testing.
Men whose medical records indicated that they had ever had homosexual or
bisexual contact were classified as MSM. Men who were not classified as MSM and
all women were classified as heterosexual. It is important to recognize that
misclassification of even a few MSM as heterosexual men would probably increase
the observed prevalence among the men classified as heterosexual.
Patients whose records indicated injection drug use were excluded from the
analyses for MSM and heterosexual men and women so that we could better analyze
the sexual transmission of HIV. Of course, misclassifying IDUs as persons who do
not inject drugs would most likely increase the observed HIV prevalence among
heterosexual patients and, to a lesser extent, among MSM.
To control for changing populations over time, we standardized data for the
trends analyses to the 1993 STD clinic population by sex (for heterosexuals),
region, race/ethnicity (black, Hispanic, white), and age group (<25 years, 25–34
years, and ≥35 years). Therefore, all HIV prevalence rates for the STD clinic
trends analyses are presented as adjusted rates, standardized to the population
of MSM or heterosexual men and women at the clinics in 1993.
This report includes only data from clinics that (1) collected data for each
year of the 5-year survey and (2) reported at least 500 total eligible specimens
or 200 eligible specimens from MSM collected during a survey period and tested
according to CDC protocol. The criteria for inclusion in this report were met by
23 STD clinics in 13 metropolitan areas. From January 1993 through December
1997, serum specimens from 12,593 MSM and 198,861 heterosexual men and women
were tested. Unadjusted HIV prevalence rates from STD clinics in all
metropolitan areas combined for the 5-year survey period were 26% (range,
8%–39%) among MSM and 2.3% (range, 0.3%–5.5%) among heterosexual men and women
(Table 2).
Men Who Have Sex With Men
Overall standardized HIV prevalence rates decreased among MSM at STD clinics
from 32% in 1993 to 21% in 1997 (Figure 2). Although HIV prevalence was high
among MSM in all regions, there were downward trends in the Northeast, the
South, and the West. (Annual data for MSM in the Midwest are not included
because the numbers of MSM tested per year were too small for meaningful
analysis). In 1993, prevalence among MSM was 36% in the Northeast, 32% in the
South, and 30% in the West. Prevalence in the same clinics in 1997 was 19% in
the Northeast, 25% in the South, and 19% in the West (Figure 3).
Figure 2. HIV Prevalence Among Patients at Sexually
Transmitted Disease Clinics, by Sexual Orientation, 1993–1997
Note. Standardized to 1993 STD clinic population by
region, race/ethnicity, and age group.
Figure 3. HIV Prevalence Among Men Who Have Sex With
Men at Sexually Transmitted Disease Clinics, 1993–1997
Note. Standardized to 1993 STD clinic population by
race/ethnicity and age group. Midwest not included because of small numbers.
The highest observed prevalence of any group included in this report was
among black MSM at STD clinics. The overall standardized prevalence for this
group was stable at 42% to 44% from 1993 through 1995 and then decreased
significantly to 29% in 1997. There was a downward trend for Hispanic MSM with
rates decreasing from 30% in 1993 to 19% in 1997. Although prevalence rates were
higher among Hispanic MSM than among white MSM for each of the 5 years, rates
for the two groups were similar by 1997 (Figure 4).
Figure 4. HIV Prevalence Among Men Who Have Sex With
Men at Sexually Transmitted Disease Clinics, by Race/Ethnicity, 1993–1997
Note. Standardized to 1993 STD clinic population by
region and age group.
Although overall HIV prevalence for white MSM decreased from 1993 to 1997,
the trends varied among the 12 clinics with sufficient data for analysis by
individual clinic. Although not statistically significant, prevalence rates were
relatively stable in one of these clinics and tended to increase in one other
clinic. For the remaining 10 clinics, prevalence declined (Appendix I). For the
combined analysis, standardized HIV prevalence rates for white MSM decreased
from 26% in 1993 to 17% in 1997 (Figure 4).
Prevalence was markedly higher among MSM who were 25 years of age or older
than among those who were younger. However, there were downward trends among MSM
in all age groups. Prevalence decreased among MSM who were 35 years of age or
older, from 36% in 1993 to 26% in 1997, and decreased among those who were 25–34
years, from 34% in 1993 to 20% in 1997. Overall prevalence decreased from 16% in
1993 to 10% in 1997 among MSM who were under 25 years old (Figure 5).
Figure 5. HIV Prevalence Among Men Who Have Sex With
Men at Sexually Transmitted Disease Clinics, by Age Group, 1993–1997
Note. Standardized to 1993 STD clinic population by
region and race/ethnicity.
Heterosexual Men and Women
Overall unadjusted prevalence rates were less than 2% among women and less
than 3% among heterosexual men at the participating STD clinics for each year of
the 5-year survey period (Figure 2). Because the HIV prevalence rates and trends
were similar for women (regardless of sexual orientation) and for heterosexual
men, we included both populations in the analysis of heterosexual patients.
There were strong regional variations in standardized HIV prevalence for this
group: approximately 4% in the Northeast, 3% in the South, and 1% in the West
and the Midwest. Prevalence decreased slightly over time in all regions (Figure
6).
Figure 6. HIV Prevalence Among Heterosexual Patients
at Sexually Transmitted Disease Clinics, by Region, 1993–1997
Note. Standardized to 1993 STD clinic population by
sex, race/ethnicity, and age group.
Prevalence among heterosexual patients at the STD clinics was highest among
blacks, followed by Hispanics and whites. For black heterosexual patients,
overall standardized prevalence was approximately stable at 2.9% from 1993–1995
and then decreased slightly to 2.4% in 1997. Rates for Hispanics increased
slightly from 1.8% in 1993 to 2.1% in 1995 and then decreased to 1.5% in 1997.
For whites, prevalence decreased from 1.7% in 1993 to 1.1% in 1994, remained
approximately stable through 1996, and then decreased to 0.7% in 1997 (Figure
7).
Figure 7. HIV Prevalence Among Heterosexual Patients
at Sexually Transmitted Disease Clinics, by Race/Ethnicity, 1993–1997
Note. Standardized to 1993 STD clinic population by
region, sex, and age group.
As was true of prevalence among MSM, prevalence among heterosexual clinic
patients was much higher among patients who were 25 years of age or older than
among those who were younger. Among heterosexual men and women who were at least
35 years old, prevalence ranged from 4.5% and 4.7% from 1993 through 1996 and
then decreased to 3.6% in 1997. For those 25–34 years of age, prevalence was
stable at 3.2% from 1993–1995 and then decreased to 2.6% in 1997. For those
younger than 25 years, prevalence during the study period remained stable at
less than 1% (Figure 8).
Figure 8. HIV Prevalence Among Heterosexual Patients
at Sexually Transmitted Disease Clinics, by Age Group, 1993–1997
Note. Standardized to 1993 STD clinic population by
region, sex, and race/ethnicity.
The data from the STD surveys probably resulted in overestimations of the
prevalence of HIV among all MSM and all heterosexuals because these clinics
serve persons whose sexual behavior has put them at high risk for exposure to
various STDs, including HIV infection. In addition, the participating clinics
may not have been representative of all STD clinics in the United States, and
the patients of these public clinics may not be representative of all patients
at STD clinics. Therefore, the HIV prevalence rates among the STD clinic
patients in these surveys cannot be generalized to all MSM or to all
heterosexual patients or even to all patients at STD clinics. In addition, some
of the patients who were classified as heterosexual could have been MSM or IDUs
who did not disclose these behaviors. Because the prevalence rates for patients
classified as heterosexual could be greatly elevated if MSM or IDUs were
misclassified, prevalence rates among heterosexual patients should be
interpreted with caution.
Injection Drug Users Entering Drug Treatment Centers
The transmission of HIV infection associated with injection drug use occurs
directly through the sharing of drug injection equipment or indirectly through
sexual and perinatal transmission from HIV-infected IDUs. Drug users entering
treatment, typically an older population than patients at STD clinics, are an
easily accessible subgroup of drug users. Unlinked prevalence surveys make use
of remnant serum specimens that are routinely obtained as part of the medical
assessment.
The DTC unlinked prevalence surveys included specimens from eligible
clients who (1) entered treatment for illicit drug use, including use of
prescription drugs for nonprescribed purposes, at least once during the past
12 months and (2) had a routine blood test performed for clinical purposes
other than for HIV testing. Persons for whom alcohol was the only drug used
within the past 12 months were not eligible for the survey. Only specimens
from eligible clients who reported ever having injected drugs were included
in the analyses for this report. To control for changing populations over
time, data for the trends analyses were standardized to the 1993 population
of IDUs entering the participating DTCs by region, sex, race/ethnicity
(black, Hispanic, white), and age group (20–29 years, 30–39 years, and ≥40
years).
Only the data from centers that collected at least 35 eligible specimens
from IDUs for each year of the survey period were analyzed. Data from 22
DTCs in 14 metropolitan areas were included in this report. Most of the
persons in the study population were seeking methadone treatment for heroin
addiction. Of the 22 DTCs, 14 were primarily methadone maintenance or
methadone detoxification centers, 5 were therapeutic community programs or
drug-free programs, 2 offered methadone detoxification and drug-free
programs, and 1 offered treatment for cocaine use.
During the study period, 36,584 eligible specimens from IDUs entering
these 22 DTCs were tested according to CDC protocol. Overall unadjusted
prevalence for male IDUs entering participating treatment centers in all
metropolitan areas was 19%, ranging from 1% in Denver and Los Angeles to 36%
in New York City; for female IDUs, unadjusted prevalence was 17%, ranging
from 2% in Denver and Los Angeles to 37% in New York City (Table 3).
Prevalence among IDUs entering DTCs differed markedly by region. In 1993, HIV
prevalence among these IDUs was 39% in the Northeast, 28% in the South, 10% in
the Midwest, and 3% in the West. By 1997, standardized prevalence rates had
decreased to 28% in the Northeast and 17% in the South. Prevalence rates in the
Midwest and the West remained approximately stable (Figure 9).
Figure 9. HIV Prevalence Among Injection Drug
Users Entering Drug Treatment Centers, by Region, 1993–1997
Note. Standardized to 1993 STD clinic population by
sex, race/ethnicity, and age group.
Overall prevalence was slightly higher among male IDUs than among female IDUs
and declined for both groups during the study period. The 1993 prevalence rate
for male IDUs was 22% in 1993 and 15% in 1997; for female IDUs, the rate was 18%
in 1993 and 14% in 1997 (Figure 10).
Figure 10. HIV Prevalence Among Injection Drug
Users Entering Drug Treatment Centers, by Sex, 1993–1997
Note. Standardized to 1993 STD clinic population by
region, race/ethnicity, and age group.
Among IDUs entering treatment, there was substantial regional variation in
HIV prevalence by race/ethnicity. In the Northeast, prevalence was high among
IDUs in each race/ethnicity group, particularly among blacks and Hispanics.
Among black IDUs, standardized prevalence rates remained approximately stable
from 1993 (46%) through 1997 (40%). Rates decreased steadily among Hispanic IDUs,
from 44% in 1993 to 31% in 1997. Among white IDUs, rates decreased from 1993
(24%) through 1995 (13%) and then remained stable through 1997 (Figure 11).
Figure 11. HIV Prevalence Among Injection Drug
Users Entering Drug Treatment Centers in the Northeast, by Race/Ethnicity,
1993–1997
Note. Standardized to 1993 STD clinic population by
sex and age group.
HIV prevalence was also high among black and Hispanic IDUs in the South. For
each year of the survey period, except 1996, prevalence was higher among
Hispanics in the South than among blacks. Although rates among Hispanics
decreased steadily, from 32% in 1993 to 18% in 1997, this decline was primarily
the result of a significant decline in one DTC in San Juan. Among blacks,
prevalence decreased from 25% in 1993 to 16% in 1995, increased to 24% in 1996,
and then decreased to 16% in 1997. Rates among whites varied from 1993 through
1995 (between 3% and 8%) and then increased from 3% in 1995 to 11% in 1997
(Figure 12).
Figure 12. HIV Prevalence Among Injection Drug
Users Entering Drug Treatment Centers in the South, by Race/Ethnicity,
1993–1997
Note. Standardized to 1993 STD clinic population by
sex and age group.
In the Midwest, the highest prevalence for IDUs entering treatment was
among Hispanics. Prevalence for this group was 32% in 1993, decreased to 19%
in 1995, and then increased to 31% in 1997. These fluctuations are probably
due to the small number of Hispanics who attended the participating DTCs in
the Midwest. Prevalence among black IDUs in the Midwest increased from 9% in
1993 to 14% in 1995 and then decreased to 9% in 1997. Among white IDUs,
prevalence was relatively stable at 5% to 8% through 1996 and then decreased
from 8% in 1996 to 4% in 1997 (Figure 13).
Figure 13. HIV Prevalence Among Injection Drug
Users Entering Drug Treatment Centers in the Midwest, by Race/Ethnicity,
1993–1997
Note. Standardized to 1993 STD clinic population by
sex and age group.
In the West, prevalence among IDUs entering treatment was substantially
higher for blacks than for Hispanics or whites. Prevalence among black IDUs
was stable at 10% to 13% for the 5-year period. Rates among Hispanic IDUs
and white IDUs in the West were stable at 2% or less for each year (Figure
14).
Figure 14. HIV Prevalence Among Injection Drug
Users Entering Drug Treatment Centers in the West, by Race/Ethnicity,
1993–1997
Note. Standardized to 1993 STD clinic population by
sex and age group.
HIV prevalence was higher among IDUs who were 30 years of age or older
than among those who were younger. Among IDUs who were at least 40 years
old, prevalence declined slightly, from 20% in 1993 to 17% in 1997. For
those who were 30–39 years old, prevalence decreased from 23% in 1993 to 15%
in 1997. For those who were 20–29 years old, prevalence decreased from 15%
in 1993 to 7% in 1997 (Figure 15).
Figure 15. HIV Prevalence Among Injection Drug
Users Entering Drug Treatment Centers, by Age Group, 1993–1997
Note. Standardized to 1993 STD clinic population by
region, sex, and race/ethnicity.
The prevalence rates obtained from this survey may not represent HIV
infection rates for all IDUs entering treatment programs, and they may not
reflect HIV prevalence among IDUs who were not in treatment. Nearly all of
the IDUs in the surveys were in treatment for heroin addiction; therefore,
results cannot be generalized to IDUs who inject other drugs. Although the
populations of IDUs in treatment and IDUs not in treatment overlap at any
given time, drug use and sexual risk behaviors in these two groups may
differ. A comparison of IDUs entering DTCs and IDUs at STD clinics in seven
metropolitan areas shows that, in general, HIV prevalence is higher among
the IDUs in drug treatment (Table 5). Because DTCs are likely to serve an
older population of IDUs whose drug use has been consistent and long-term,
the DTC population is more likely to be HIV-positive, especially in cities
where HIV prevalence among IDUs is high.
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