Collecting blood samples in international surveys is challenging. While venous blood samples (VBS) from blood serum are the reference values for clinical chemistry, the costs of VBS are prohibitive for a large international population-representative survey. The advantage of collecting dried blood spot (DBS) samples rather than VBS is that DBS can be collected by lay interviewers at much lower costs while VBS require nurses (Williams and McDade 2009, Brindle et al. 2014).
The disadvantage of DBS, however, is that laboratory results from DBS assays cannot be directly compared to the results one would obtain from assays of venous reference samples using standard laboratory methods (McDade et al. 2007, Crimmins et al. 2013; Karvanen 2015). While reference values have measurement variation, DBS values of, e.g., total cholesterol, which is known to be particularly difficult to measure in DBSS, have both a larger mean and a larger variance, influenced by many laboratory and fieldwork-related factors (Thomas et al. 2018; Crimmins et al. 2020; Bowen & Evans 2014. In: Li & Lee 2014). After applying parametric standardization (Karvanen, 2015) or non-parametric normalization formulae (e.g. Crimmins et al. 2013), the DBS values fit the distribution of values obtained from venous blood quite well. This approach has been used with HRS data to produce adjusted values for a small set of analytes (Crimmins et al. 2013).
Recent work has shown that these adjustment formulae do not suffice to account for fieldwork conditions which may affect the quality of DBS taken in an international survey like SHARE (Weiss and Börsch-Supan 2019). This finding has been replicated in two field studies which collected both VBS and DBS (Weiss et al. 2019, Crimmins 2019).
This paper applies a systematic approach to validate DBS results in the laboratory by simulating SHARE fieldwork conditions. We call them “structured validations” because our methodology is based on a structural model of the differences between VBS under laboratory conditions and DBS under fieldwork conditions. We use these validations to establish conversion formulae applicable to the SHARE populations, which estimate the value that we would have obtained had it been feasible to analyze a donor’s venous blood with standard analytical methods (reference value).
