Page 26 - Epidemiological studies on tuberculosis control and respiratory viruses

Chapter 6
Methods
Study population
HELIUS study
The HELIUS study (acronym for Healthy Life in an Urban Setting) is designed as a large prospective cohort study, initiated by the Academic Medical Center (AMC) and the Public Health Service of Amsterdam, to understand the unequal burden of disease across ethnic groups [8]. People aged 18-70 years, of Dutch, Turkish, Moroccan, Ghanaian, Surinamese origin were sampled from the municipal civil register of Amsterdam and invited to participate. Sampling was random but stratified by ethnicity, as defined by the country of birth of individuals or their parents as documented in the civil register [8]. Persons who were unable to give informed consent and persons who were not registered with a general practitioner were excluded. Baseline data collection started in January 2011 and is still ongoing. Data are collected through a questionnaire and physical examination, and biological samples are obtained during study visits.
During the data collection from January 2011 until June 2013, nasal and throat swabs were obtained by trained nurses or research assistants using flocked swabs (FLOQSwabsTM, Copan, Brescia, Italy) and collected in a single tube containing 3 mL of viral transport medium (UTMTM medium, Copan, Brescia, Italy). The transport medium was kept at room temperature until transport to the AMC Department of Medical Microbiology on the same day. On arrival, the tubes containing the combined swabs and transport medium were vortexed, the swabs were discarded, and the medium was divided into two equal aliquots and stored at -80°C until further processing [8].
Before the physical examination at the study site, participants were asked by a trained research assistant, if they currently experienced any of the following seven symptoms: fever, headache, muscular pain, cough, a sore throat, shortness of breath, or a runny nose, or had experienced these symptoms in the 2 weeks preceding the day of the examination.
At the time of study initiation few participants of Turkish and Moroccan origin had been recruited, and therefore only participants from three ethnic groups (Dutch, Surinamese and Ghanaian) were selected for inclusion in the current study. Of participants recruited during the influenza seasons (October – March) in the years
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