Discussion
hypercholesterolaemia
DISEASE, HYPERCHOLESTEROLAEMIA
Our findings suggest that, while response rates for self-collected DBS samples are around half that in a nurse visit, characteristics of participants are unbiased with respect to educational attainment, self-rated health and longstanding illness. While measurement quality of HbA1c and HDL-cholesterol may be inconsistent by DBS, a high proportion of DBS samples were classified as ‘good’, and DBS can be a cost-effective alternative in large-scale surveys/studies to assess sub-clinical and clinical disease burden.Our findings suggest that DBS collection is a feasible collection method. The analyses presented generally accord with findings from other population studies that have introduced self-collection and observed reduced response ratesWe developed reliable methods for the collection of DBS and measurement of total cholesterol, triglycerides, CRP and HbA1c in DBS but less successfully for the measurement of HDL-cholesterol in accordance with someDespite these constraints, equivalence of the DBS data to predict prevalence of disease from the self-collected study samples suggested that equivalence was sufficient for us to accurately describe population prevalence of hypercholesterolaemia and elevated CRPOur study has a number of strengths. Unlike previous studies we randomly assigned households to receive a nurse visit to collect a venous and DBS sample. Our findings of similar clinical characteristics by mode of collection, as would be expected in a well randomised study, provide more robust findings of equivalence. Thus, our study is not subject to the biases associated with earlier observational studies. Our study is large, spans the adult age range and our sampling strategy means that we can make population level inferences through the use of inverse probability weighting. The analysis of a proportion of samples was delayed with the closure of laboratories during the COVID-19 pandemic, which enabled us to examine delay of measurement in our analyses previously described to impact integrity of measurements in the DBSWe conclude that while self-collection of DBS samples is feasible, there are lower response rates than in face-to-face sample collection. However, the use of DBS permits large scale collection in an unbiased way that would enable comparable population disease estimates as from venous samples collected by a nurse. We recommend DBS for large scale studies of cardiovascular risk factors collected by participants themselves. Research supports the collection of samples for a wider range of analytes and measures