Collecting biomeasures in a social survey: comparing a nurse-only approach with an interviewer>nurse approach in BCS70.
Jul 25, 11:30
The inclusion of biomeasures within social surveys, and longitudinal surveys in particular, is becoming ever more common. Combining objective measurements of health with detailed information about lifestyles and behaviour collected over long periods of time offers enormous research potential.
Studies which combine an interview with biomeasures can be conducted in various ways. One model is that field interviewers make initial contact with participants, conduct the interviews and arrange follow-up visits for a nurse to perform the biomeasures. The main disadvantage of this approach is an inevitable degree of attrition between the interview and the biomeasures. Another model is to train field interviewers to collect biomeasures but there remain questions about whether the quality of data collected is comparable to that collected by a nurse, and some evidence suggests that field interviewers take longer to carry out such measures which can increase costs. In addition, field interviewers cannot take intravenous blood. Other studies invite participants to visit clinics, but this can be very costly in a large-scale national study. There is no consensus on the optimal strategy for combining a social survey with the collection of biomeasures.
The 1970 British Cohort Study (BCS70) is a longitudinal birth cohort study which began in 1970. The 11th sweep of the study began in 2016, when study members were aged 46, involves an interview (50 minutes) and a detailed series of biomeasures including the collection of a blood sample (50 minutes).
The first phase of fieldwork was conducted using a new approach where nurses conducted all of the data collection - i.e. they contacted participants and then conducted the interview and biomeasures in one visit. This approach was considered advantageous on the basis that it would maximise response to the biomeasures by reducing attrition between the interview and nurse visit; would maximise the quality of the biomeasures collected, and the efficiency of using one data collection agent would reduce costs. Nurses are however less experienced at contacting and tracing participants, maximising co-operation and conducting interviews as these activities would normally be conducted by field interviewers. Mid-way through fieldwork BCS70 switched to a two stage approach where interviews are conducted by interviewers followed by a separate nurse visit. This presents a unique opportunity to evaluate the success of the two approaches. The paper will compare the 'nurse-only' and two-stage 'interviewer>nurse' model in terms of interview response rates, biomeasure response rates and measures of data quality.