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Research Letters

Time trend in incidence of HIV seroconversion among homosexual men repeatedly tested in Madrid, 1988–2000

del Romero, Jorgea; Castilla, Jesúsb; García, Soledada; Clavo, Petuniaa; Ballesteros, Juana; Rodríguez, Carmena

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An open cohort of 2670 homosexual men repeatedly tested for HIV at a Madrid clinic has registered 8050 person-years (PY) of follow-up and 157 seroconversions from 1988 to 2000. After declining from 1988 (4.71 per 100 PY) to 1995 (1.06 per 100 PY), the incidence rate began a significant upward trend, reaching a figure of 2.16 per 100 PY in 2000. These findings ought to alert surveillance systems and prevention programmes.

The early 1990s witnessed advances in the control of HIV transmission among homosexual men in western European countries [1]. HIV seroprevalence among homosexual and bisexual men voluntarily tested at a Madrid clinic fell from 30% in 1990 to 12% in 1994 [2]. Recently, increases in the incidence of sexually transmitted diseases (STD) and sexual risk practices have been detected in homosexual men [3,4], but there is no clear evidence of an increase in HIV transmission [5].

We have analysed the time-trend in HIV seroconversion among homosexual men repeatedly tested for HIV at Madrid's largest STD/HIV diagnostic clinic in the period 1988–2000. This clinic provides free medical attention to all patients on demand, including anonymous voluntary HIV testing and counselling. During the first visit, each patient was assigned a code, which allowed for a record to be kept of the results, and was thereafter maintained for all successive visits to the clinic. Regular examinations were offered to all seronegative patients reporting risk practices. HIV diagnosis relies on enzyme-linked immunosorbent assay testing and Western blot confirmation. The results of all HIV tests performed at the clinic were prospectively computerized, along with the relevant date, patient code, sex, age and HIV risk exposures.

An open cohort was formed, including all homosexual men who had no record of drug injection, had undergone a first negative HIV test, and had repeated the test at least once at the clinic between 1988 and December 2000. Individuals with less than 90 days between their first and last tests (n = 14) or with periods of over 5 years without repeat testing (n = 92) were excluded. Annual HIV incidence rates were calculated by taking the PY of follow-up per calendar year as denominators. The numerators were obtained under the hypothesis of the uniform distribution of HIV seroconversions over the period between the last negative and first positive tests. For example, an individual who had tested negative for HIV in April 1990 and positive in May 1991 contributed as a case for 8/13 in 1990 and for 5/13 in 1991 [6].

The 2670 patients making up the cohort registered a total of 8050 PY of follow-up and 157 seroconversions from 1988 to 2000. The average number of HIV tests per patient was 3.7 and the median time between two successive tests was 13.7 months. Among seroconverters the median time between the last negative and first positive tests was 13.1 months (range 3–59 months). The mean age at first visit was 29.4 ± 8.2 years and held steady throughout the period. After declining from 1988 (4.71 per 100 PY) to 1995 (1.06 per 100 PY), the incidence rate has registered a progressive increase, reaching a figure of 2.16 per 100 PY in 2000 (Table 1). Poisson regression analysis showed a slight but statistically significant upward trend from 1995 to 2000. Such a trend became more pronounced after adjusting for age (< 30 and ≥ 30 years) and the time from the beginning of follow-up (< 24 and ≥ 24 months), giving a rate ratio for the annual increase of 1.41 (95% confidence interval 1.07–1.85).

Table 1:
HIV incidence among homosexual men repeatedly tested in Madrid, 1988–2000.

Caution is called for in the interpretation of these results because of the selection biases inherent in the studies. However, the clinic that served as the setting for this study is well established among Madrid's gay community by reason of its location, ease of access and offer of free anonymous HIV testing. During the study years, no noteworthy changes took place in the features and functioning of the clinic. In addition, only test results obtained at the clinic itself were considered, unlike other studies that include patients’ self-reported results [7].

The incidence of HIV, ascertained through follow-up studies, is the most sensitive measure of recent shifts in HIV transmission, inasmuch as it analyses infections on the basis of the date on which they occur. Despite this, few studies have analysed the corresponding trend over time. HIV diagnosis reporting systems and seroprevalence surveys can take several years to detect changes in the incidence of HIV.

We detected a moderate increase in the incidence of HIV among homosexual men repeatedly tested in Madrid over the period 1995–2000, thus reversing the downward trend of previous years. This new increase in HIV transmission is in the line with the increase in the incidence of gonorrhoea and the frequency of sexual risk practices recently found among homosexual men in other European countries [3–5]. A report has recently described an increase in HIV incidence among repeated testers in San Francisco [7]. These findings ought to alert surveillance systems to confirm and analyse this new situation. In the meantime, prevention has been intensified to avoid any relaxation of safe-sex practices, by seeking more attractive ways to disseminate the message, so as to reawaken the interest of the homosexual population in general and the youngest segment in particular.

Jorge del Romeroa

Jesús Castillab

Soledad Garcíaa

Petunia Clavoa

Juan Ballesterosa

Carmen Rodrígueza


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© 2001 Lippincott Williams & Wilkins, Inc.