Recruitment and sampling: mission accomplished!
Adequate recruitment and sampling procedures are the first step towards a successful HBM study. Knowing that, COPHES provided scientific support for a harmonised recruitment of study participants and the collection of samples in a European population-based HBM study.
The team dealing with recruitment and sampling elaborated a report on the relevant existing practices to conduct population-based studies in Europe. On this basis, the team prepared general guidelines describing different options for the choice of an adequate population segment, for the recruitment process and for conducting field work and interviews.
The final suggestions were integrated into the study protocol, with clear recommendations and examples of standard operation procedures to guide the implementation of the pilot study, DEMOCOPHES, and test the feasibility of the proposed procedure.
Quality assurance methods for conducting the field work were also developed, including: detailed guidelines on single procedures, the so-called Fieldwork Manual, training programmes for the interviewers, as well as internal and external quality control measures. In addition, questionnaires which were used during the field work to obtain information on nutritional and lifestyle behavior of study participants were made available.
These instruments, developed within COPHES, were applied in all 17 countries participating in DEMOCOPHES, ensuring a successful survey conduct.
In each country, an urban and a rural area were chosen as sampling locations. In 14 countries children were recruited via schools to participate with their mothers in the survey. The other 3 countries got addresses of families from population registries and 120 mother-child pairs took part in the study after being invited via invitation letters sent by mail.
Trained interviewers visited the selected families at home,or mother and child visited an examination centre (e. g. a room in the child’s school) to be interviewed and to provide the urine and hair samples. For the interview, the questionnaires developed by COPHES were translated into national languages and properly applied – after all, field workers had been successfully trained during a train-the-trainer session for field work (see work package TRAINING). All proposed quality assurance methods recommended in the SOPs were also followed.
At the end of the recruitment and sampling phase, the feasibility of a harmonized EU-HBM survey regarding recruitment and field work based on the developed procedures was clearly demonstrated.