Subgroup analyses were conducted to assess differences in the effect sizes of the different classes of biomolecules, analytical techniques, substrate porosity, blood source, temperature and type of summary statistic reported. This was completed using three-level mixed-effects models specifying the subgroup to be evaluated . Unless indicated otherwise in the studies, the ambient temperature was regarded as room temperature (18 -25°C). Effect sizes and confidence intervals for each subgroup were plotted for visual comparisons; F statistics and p-values were recorded.