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Seroprevalence of HIV Among Sexually Transmitted Infections Clinic Attenders Voluntarily Tested for HIV in Barcelona, 1998–2001

The Primary Care STI Study Group (GITSAP)


Background: Spain has been the European country most affected by the AIDS epidemic, and sexual transmission now accounts for the majority of cases of HIV.

Goal: The goal was to describe HIV prevalence and risk profiles among people tested for HIV in Barcelona in 1998 to 2001.

Study Design: We studied cross-sectional HIV surveys among sexually transmitted infection clinic attenders. We performed quantification of risk factors for HIV infection through odds ratios (ORs) and logistic regression.

Results: The prevalence of HIV among the 4993 persons tested was 1.8% (95% confidence interval, 1.5–2.2) without significant changes across the years. HIV prevalence in homo-/bisexual men was higher (P <0.001) at 4.8% than heterosexuals. Although men aged older than 30 compared with those younger were at increased risk, 2.56), young homosexual men were at higher risk (OR, 17.84) to be infected than young heterosexuals.

Conclusion: HIV prevalences were relatively low among all heterosexuals, but much higher among homosexual and bisexual men. The potential exists for ongoing sexual HIV transmission among homo-/bisexual men in Barcelona.

The HIV prevalence in a sexually transmitted infection clinic in Barcelona was 1.8%. Homo-/bisexual men had higher prevalences than heterosexuals. Although men aged older than 30 were at increased risk of HIV infection, young homosexual men were 18 times at higher risk than young heterosexuals.

STI Unit, Service of Primary Care Ciutat Vella, Catalan Health Institute, Barcelona, Catalonia (Spain)

*The Primary Care STI Study Group (GITSAP): Encarnación Arellano, RN, Maria J. Alcalde, RN, Pere Armengol, MD, Josep M. Escribà, MD, Eva Loureiro, Dipl Stat, Pilar Saladié, RN, Benicio Sanz, MD, Mirjana Saravanya, MD, Martí Vall Mayans, MD, and Maria J. Villena, RN, (STI Unit, Service of Primary Care Ciutat Vella, Barcelona); and Isabel Rodrigo, Lic Pharm, and Marta Ris, Lic Biol (Manso Clinical Laboratory, Service of Primary Care Eixample, Barcelona). Analysis and writing committee: M. Vall Mayans, E. Loureiro, and J. M. Escribà.

Supported partially by the Spanish Foundation for AIDS Research and Prevention (FIPSE) (grant no. 3.076/99), this article contributes in part to the “Prospective Study About the HIV Prevalence Among Patients From a Network of STD/HIV Centers (The EPI-VIH project).”

Correspondence: Dr. M. Vall Mayans, STI Unit, Service of Primary Care Ciutat Vella, Catalan Health Institute, Av. Drassanes 17-21, 08001 Barcelona, Catalonia, Spain. E-mail:

Received for publication February 24, 2003,

revised July 8, 2003, and accepted July 16, 2003.

PATIENTS ATTENDING SEXUALLY transmitted infections (STI) clinics, either seeking treatment for STI or testing for HIV, could be considered at increased risk of acquiring or passing HIV sexually. 1 Data from those patients can act as an early warning, because it has been shown that decreasing rates of new AIDS diagnoses, especially following large-scale introduction of highly active antiretroviral treatment (HAART), would not reflect stable rates of new HIV infections among homosexual men and heterosexual patients attending these clinics. 2 On the other hand, dramatic increases have occurred in STI and in sexual risk behavior among homosexual men in several major cities internationally, 3–5 and recent outbreaks of syphilis and gonorrhea have been detected in developed countries, including Catalonia, Spain. 6–8

Spain has been the European country most affected by the AIDS epidemic over the last decade, with intravenous drug users (IDU) being the main transmission group by far. However, it has been estimated in 2001 that sexual transmission (15–25% homosexual and 20–30% heterosexual) already accounts for more cases of HIV than transmission among IDU parenterally. 9 HIV surveillance data from STI patients in Spain has been scarce. To mitigate this situation, a multicenter project, which includes the STI Unit of Barcelona, was launched in 2000 to monitor HIV time-trends among patients from STI and HIV diagnosis clinics (The EPI-VIH Project). 10 We describe risk profiles and HIV among people voluntarily tested for HIV in Barcelona during the years 1998, 2000, and 2001.

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The STI Unit of Barcelona is the only specialized STI center of Barcelona, and it is located in the historic old district of Ciutat Vella. The district has the lowest socioeconomic indicators of Barcelona, and it is still a popular place for the practice of street prostitution. The STI Unit offers voluntary, confidential, and free services for STI treatment and HIV testing to any person requesting them without the need to show identity documents. Testing for HIV was done on request or was offered by health professionals to people practicing prostitution and to people with or without STI symptoms considered at risk for HIV. In all situations, HIV testing was accompanied by pre- and posttest counseling. Blood specimens were screened for HIV by enzyme immunoassay, and reactive sera were confirmed with Western blot or synthetic peptides. For the purpose of this study, epidemiologic data were collected in a structured questionnaire retrospectively for 1998 (January–June) and prospectively for 2000 (May–December) and 2001 (January–December) for people newly tested for HIV. The main items collected in the questionnaire by patient self-reports were sex, age, sexual orientation, practice of prostitution, use of intravenous drugs, and origin according to country of birth. Information about sexual practices was not collected. When a person had been tested more than once in a given year in 1998, 2000, or 2001, only the last result in that year was included, and duplicates were excluded. Completeness of all subjects who had an HIV test during the study periods was assessed linking the database of the questionnaires with that of the blood results from the laboratory by means of the patient identification unique code. Persons with documented HIV infection attending the STI Unit during the study periods were excluded to avoid bias. Proportions were calculated with 95% confidence intervals (95% CI) and compared with Fisher's exact test. Chi-square for trend was also calculated. To measure the association between HIV infection and risk factors, odds ratios (OR) and their 95% CI were calculated for each level, and multiple logistic regression was used to assess the independent influence of each factor on the risk of HIV infection in relation to other factors included in the model.

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During the years of the study, approximately 10,000 persons (60% men) visited the clinic annually. A total of 4993 persons were tested for HIV during the periods of observation: 2818 men (39.7% of them homo-/bisexuals) and 2175 women (32.7% of whom practiced prostitution). The characteristics of the persons that did not change across the years (data not shown) were age (mean, 30 y), proportion of men (56%), and proportion of people practicing prostitution (16%). Significant trends (P <0.001) were observed for the proportion of heterosexuals (from 80% in 1998 to 73% in 2001) and for the proportion of foreign people tested (from 19% in 1998 to 39% in 2001). During the 3-year study periods, the overall point prevalences were 1.6% (95% CI, 0.9–2.5) in 1998, 1.7% (95% CI, 1.1–2.5) in 2000, and 2.0% (95% CI, 1.5–2.6) in 2001, without significant changes across the years (P for trend = 0.8).

The HIV prevalence increased progressively with age, this being more evident among those older than 30 years. Table 1 shows the HIV prevalences in 3 groups by sex and sexual orientation in men (heterosexual and homo-/bisexual) stratified by age groups (equal and younger than 30 or older than 30). No significant trend over the years was observed in any of the 3 groups (data not shown). With the exception of women, aggregated data for the 3-year period in each group showed significantly higher prevalences in people older than 30 in heterosexual men (P = 0.01) and homo-/bisexual men (P = 0.02). Sex was not a confounder of the association between age and HIV infection (adjusted OR, 2.12; 95% CI, 1.35–3.29). However, a significant (P <0.001) interaction existed between age and sexual orientation in men. Among heterosexual men >30 years, risk of HIV infection was 7 times higher than those younger or equal than 30, whereas among homo-/bisexual men, the risk was 2 times higher in the same age groups (Table 1). Of interest was that risk of HIV infection among men ≤30 was 17 times higher in homo-/bisexuals compared with heterosexuals, and that among men >30, it was “only” 5 times higher in homo-/bisexuals compared with heterosexuals (Table 2). A significant (P <0.001) linear trend also existed for the increased risk of HIV infection from young heterosexuals to older homo-/bisexuals (Table 2).

HIV prevalences in heterosexual men and women were approximately 1% (0.7% in men and 1.1% in women; P = 0.2). Nevertheless, heterosexuals had significantly (P <0.001) lower HIV prevalences than homo-/bisexual men (4.8%). Considering that we did not control for receptive-anal intercourse, no significant factor for HIV infection was identified in women (Table 3). Among men, those aged older than 30 compared with those younger than that age were at increased risk (OR, 2.56 [95% CI, 1.53–4.27]), and homosexuals (OR,7.64 [95% CI, 3.93–4.85]) and bisexuals (OR, 6.42 [95% CI, 3.11–3.23]) were also at significantly higher risk to be infected than heterosexuals. In different logistic regression models adjusted for potential confounders in Table 3, these factors remained significantly associated with HIV infection in men, with similar ORs (data not shown).

Finally, Table 4 shows the characteristics of the persons who tested HIV-positive during the study period by origin: 55 autochthonous (61%) and 35 foreigners (39%). Notably, foreigners were significantly younger (P = 0.005) and also had a higher proportion of women (P = 0.02) than autochthonous.

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The results presented here summarize HIV seroprevalence data from 1 of the 3 referral STI Units of Catalonia (6 million inhabitants) in Spain; over 80% of the STI/HIV activity of those 3 Units is carried out in the STI Unit of Barcelona (Barcelona's population: 1,645,000). It must be recognized that voluntary testing to measure HIV prevalence in STI clinics leads to participation bias, 11 and that patients not tested have been found more likely to be infected than were patients who were tested. 12 Hence, considering that we also excluded those with documented HIV infection, our estimates reflect the minimum prevalence of HIV infection among the attendees of our Unit.

Like in Western Europe, 13 the HIV epidemic in Catalonia, Spain, is now endemic, and sexual transmission among heterosexual men and women seems to account for an increasing proportion of new HIV infections and AIDS cases. 9 However, IDU and homosexual men, although relatively much smaller in population size, remain very probably those most at risk. Our data show stable relatively low HIV prevalence rates below 2% overall and in heterosexual attenders. Also, they show stable prevalences among homo-/bisexual men that they are, however, significantly much higher than those of heterosexuals overall (4.8% vs. 0.9%, respectively). A pattern similar to that of the STI Unit of Barcelona, with the exception of IDUs who were underrepresented in our Unit, was also found in other centers of Spain. 14

Generally, homosexual and bisexual STI clinic attenders show significantly higher HIV prevalence rates than heterosexuals, the magnitude of the difference being influenced by other associated risk factors like IDU, prostitution, or minority. 2,14,15 Three surveys among homosexual men recruited in gay sites (saunas, sex shops, cruising sites) carried out between 1995 and 2000 in Barcelona 16 found stable prevalence rates of HIV approximately 15% and of unprotected anal intercourse with casual partners approximately 23%. Nevertheless, the proportion of men with more than 10 male sexual partners increased in 2000, from 45% to 58% (P <0.001); a significant trend was also found regarding an optimistic perception about antiretrovirals and of using different recreational drugs during sexual encounters. Taken together, the data would suggest that there have not been recent increases in HIV infection and risky sexual behavior among homosexual men in Barcelona compared with other European cities. 3,17,18 However, the situation also suggests that there is a clear potential for ongoing sexual HIV transmission among homosexual men in Barcelona. In addition, we have detected increases in infectious syphilis 8 and gonorrhea (data not shown) diagnoses in our STI Unit since 1998, which correlate with unsafe sexual practices and predict risk of acquiring HIV infection in homosexual men. 19 If this trend persists, it could be a matter of time to see HIV increases among homosexual men in Barcelona too.

We found HIV prevalences in heterosexual men and women of approximately 1%, without differences between men and women, and female prostitutes. The figures equal those found within the network of 18 Spanish STI/HIV clinics of the EPI-VIH Project. 20 It has been estimated in 2001 that heterosexual transmission could account for 20% to 30% of cases of HIV in Spain. 9 The heterosexual HIV epidemic in Spain is concentrated, linked mainly to IDU 9,10,14 and more recently to migrants from generalized epidemics, 20 similar to that found in other European countries where immigrants account for a large and increasing proportion of reported HIV/AIDS cases. 13,15,21,22 It remains to be explored in our setting the contribution of HIV transmission from bisexual men to female sex partners. 23

We might have not been able to detect changes in HIV infection over time because seroprevalence surveys take several years to detect changes in incidence. Ideally, when cohort studies are not affordable, new testing algorithms should be used to assess more precisely rates of new HIV infections. 2 STI clinics play an important role in HIV prevention and control because routine HIV screening in STI clinics is cost-effective, 24 and also because HIV surveys provide critical indicators in monitoring the HIV epidemic. 1

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