Overview of the Amsterdam cohort studies among homosexual men and drug users

Introduction

The Amsterdam cohort study (ACS) of Human Immunodeficiency Virus (HIV) infection and AIDS among homosexual men was started in 1984, followed shortly by the Amsterdam cohort study among drug users in 1985. The ACS is a collaboration of the Municipal Health Service, the Department of Human Retrovirology, the AIDS unit of the department of infectious diseases and the International Antiviral Therapy Evaluation Center (IATEC) of the Academic Medical Center, University of Amsterdam and of the Department of Clinical Viro-immunology, CLB division of Sanquin Blood Supply Foundation and Laboratory for Experimental and Clinical Immunology.
This overview is primarily written for these collaborators and to give an understanding of the main characteristics of the Amsterdam cohort studies. The various subgroups and studies are briefly described, followed by tables with numbers of participants under follow-up and HIV incidence over calendar time.

Questions regarding this overview can be addressed to:
Anneke Krol, Datamanager Amsterdam cohort studies
Municipal Health Service Amsterdam
E-mail: akrol@gggd.amsterdam.nl
Telephone: 020-555 5302

1 October 2001


Amsterdam cohort study among homosexual men


The study population consists of homosexual men living mainly in and around the city of Amsterdam, The Netherlands. Table 3 shows how many participate(d) in ACS among homosexual men and its substudies. The first wave of enrolment took place between October 1984 and April 1985 (Protocol 1). Included were asymptomatic homosexual men aged 18-65 with at least two sexual partners in the six months prior to intake. They were recruited through announcements in the gay press, advertisements and by word of mouth. Between April 1985 and February 1988 only seronegative men could enter the study (Protocol 2). Enrolment was re-opened to HIV-1 infected individuals from February 1988 until December 1998 (6000 numbers). Some of these participants entered the ACS because they were found to be HIV positive while participating in another Municipal Health Service study or to start with antiretroviral treatment (open and doubleblind AZT study). In June 1995 a special recruitment campaign was started among young (<=30) homosexual men, a study which is still ongoing. In February 1996, the follow-up of the 'old' HIV seronegative participants was terminated. Finally, a few participants entered the ACS but could not be classified in either of the abovementioned studies (9000 numbers) or were allowed to start their treatment within the ACS from February 1997 onwards (7000 numbers).
In February 1999, follow-up of all HIV infected participants was transferred to the Jan van Goyen clinic in the scope of the National Athena monitoring project.

Daily routine

Seropositives and seroconverters are seen every three months. Clinical, epidemiological and social scientific data are collected with standardised questionnaires (six monthly, co-ordinated by the department of Social Science, University of Utrecht) and by physical examination. Blood is taken for virological and immunological tests and for storage. Seronegatives are seen by a nurse every six months and similar data are collected but no immunological tests are done nor are cells stored.
Participants who developed an AIDS event during follow-up were referred to the AMC and since 1996 much effort has been put into aligning the AMC and the ACS registry regarding events (clinical follow-up). AIDS cases are also ascertained through cross-linking with the Amsterdam AIDS registry.
Once a year information on survival status is obtained through active follow-up and matching with local population registries. The cause of death is obtained from the Amsterdam AIDS surveillance registry, hospital records and from next of kin.

Intervention/vaccination studies

At the beginning of 1987 a preliminary study of AZT in asymptomatic HIV infected subjects was started within ACS. Followed one year later in April 1988 by a multi-centered double-blind-placebo-controlled study. Since then ACS has participated in several different (multi-centered) trials like Delta, Triple, Atlantic, Prometheus, Native and D4T/3TC study.
ACS has also participated as a study-site in three vaccination studies. Recruitment of the P24-HIV and rgp120 study among HIV positives started between March 1993 and March 1994. The Vaxgen (multi-centered) double-blind placebo-controlled study among high risk HIV uninfected homosexual men started in 1999 and is still ongoing.

Amsterdam cohort study among drug users

Participants are recruited at methadone outposts, the weekly STD-clinic for drug-using prostitutes and by word of mouth. HIV negative and asymptomatic HIV positive injecting and non-injecting drug users (IDU and non-IDU) are invited to participate. Table 6 shows how many participate(d) in ACS among drug users and its substudies. The first wave of enrolment took place between December 1985 and September 1990 whereafter inclusion stopped until August 1991. Enrolment was then re-opened and in 1998 a special recruitment campaign was started among young drug users (<=30 years). Although it was a cross sectional study design, a quarter is being followed in the drug user cohort. Again, in June 2000, much effort was put into recruiting young drug users. This follow-up study is still ongoing. From February 2001 'old' drug users can no longer enter the study.

Daily routine

Participants are seen every four months regardless of HIV status, but many return more irregularly. Clinical, epidemiological and drug use related information is collected at each occasion by interviewing participants using a standardised questionnaire. Since April 1989 this questionnaire was thoroughly revised and all participants were physically examined by a physician at each visit. In January 1999 this examination was terminated for the HIV negatives. Blood is taken for virological tests and storing and from April 1989 immunological tests are part of the daily routine in HIV negative as well as HIV positive participants. Since 1995 these are limited performed in a small subset of the HIV negatives.
Data on hospitalisation are collected at each visit from the participants, independently through the Drug Department of the Municipal Health Service and since 1997 for all seroconverters and HAART using drug users effort has been put into aligning hospital and ACS event registration (clinical follow-up). Cases of AIDS are also ascertained through cross-linking with the Amsterdam AIDS registry. After AIDS has been diagnosed drug users can still participate.
Yearly, deaths and causes of death are identified by determining participants' vital status at the register of population in their city of residence and through locating and examining hospital records and coroners' reports.

Substudies

Several substudies have been done among the drug users. Participants were tested for Hepatitis A, B and C, HTLV-1 and 2 and haematology. Also in depth interviews were held to investigate why participants stopped injecting drugs. Furthermore there is a close collaboration with the STD clinic of the Municipal Health Service and the Central Methadone Registry.