In general this doesn&#x27;t seem like huge surprise. Blood is reasonably homogeneous, but noise becomes an issue when you&#x27;re looking for anything present in low concentration (signal close to the noise floor) or when small differences in concentration matter (signal superimposed on background noise causes the value change from expected to be close to the magnitude of the noise).<p>If noise is too high for a single drop, a venous draw is a much larger volume and theoretically equivalent to sampling many drops of blood—it&#x27;s the physical equivalent to averaging samples to increase the SNR.<p>The authors note[1] that averaging may not be enough though, and that there may be an interesting difference inherent to fingerprick blood (possibly caused by their collection method):<p>&quot;Our data also suggest that collecting and analyzing more fingerprick blood does not necessarily bring the measured value closer to those of the donor’s venous blood (Figures 1D and 2D). For example, donor B’s hemoglobin and WBC concentration were similar for venous blood and fingerprick in drop 1 but became less concordant with additional drops, while donor C’s fingerprick measures came closer to the venous measures with additional drops. These data may represent true differences between fingerprick and venous blood, or they may be the result of errors in collection (such as leaving the tourniquet on for too long during a venous draw). Further research is needed to determine how common these patterns are.&quot;<p>1. <a href="http:&#x2F;&#x2F;ajcp.oxfordjournals.org&#x2F;content&#x2F;ajcpath&#x2F;144&#x2F;6&#x2F;885.full.pdf" rel="nofollow">http:&#x2F;&#x2F;ajcp.oxfordjournals.org&#x2F;content&#x2F;ajcpath&#x2F;144&#x2F;6&#x2F;885.ful...</a>