ACS among people who use drugs (PWUD)
As of 31 December 2016, 1,680 PWUD were included in the ACS and contributed 28,194 visits. In 2014, the cohort was closed to new participants. Regular follow up of PWUD continued until February 2016. All PWUD who had ever participated in the ACS were then invited for an end-of-study interview and follow up was successfully ended in July 2016. Research using ACS data on PWUD is still ongoing.
Before 2014, participants visited the GGD Amsterdam every four to six months. They completed a standardised questionnaire designed to obtain information regarding medical history, sexual and drug use behaviour, underlying psychosocial determinants, healthcare use, depression, psychological disorders, and demographics. In addition, HIV-positive participants, and in the past also HIV-negative participants, underwent a medical examination. Blood was collected for diagnostic tests and storage.
In 2014, the cohort was closed for new participants and PWUD included in the ACS were divided into two groups in line with the advice of the international scientific advisory committee in 2013. Group 1 consisted of PWUD who visited the GGD Amsterdam once a year to complete questionnaires with no testing and blood sampling. Group 2, the focus group, consisted of PWUD who were 1) HIV positive; 2) hepatitis C virus (HCV) seroconverters; 3) multiple-exposed, non-infected with HIV and HCV, and 4) a random control group. This group visited the GGD Amsterdam twice a year for testing and blood sampling and to fill out questionnaires, as in previous years. Regular follow up of drug users continued until February 2016.
Finally, all drug users who had ever participated in the ACS were invited for an end-of-study interview. A total of 182 end-of-study interviews were held between February and July 2016, after which the follow up of drug users was successfully ended.
Of the 1,680 PWUD, 323 were HIV-positive at entry, and 99 seroconverted during follow up. The figure shows the yearly-observed HIV incidence rate for PWUD and people who injected drugs (PWID) from the start of the ACS through the end of 2012. The HIV incidence declined over time and stabilized after 1999 at almost zero new infections per 100 person years. The last HIV seroconversion was seen in 2012.
By 31 December 2016, 576 deaths had been confirmed among PWUD. The median age of the PWUD who visited the ACS in 2016 was 55 (IQR 49-59), 8.1% had attained a high level of education, and 63.4% were born in the Netherlands.