I think they can't make a strong claim about it but some of the donors didn't seem to have the same results from an average of the drops and the other blood draw
> 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.
Also:
> Morris et al7 believe the higher variability of capillary blood compared with venous blood is due to the presence of extracellular fluid in capillary samples. In clinical practice, milking of the finger by insufficiently trained health care workers may result in even greater drop-to-drop variability than shown here.
This may present more of a risk for at-home testing if you need to make sure that the person hasn't squeezed their finger at all.
Quite an interesting set of problems that I'd not really considered before.
> 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.
Also:
> Morris et al7 believe the higher variability of capillary blood compared with venous blood is due to the presence of extracellular fluid in capillary samples. In clinical practice, milking of the finger by insufficiently trained health care workers may result in even greater drop-to-drop variability than shown here.
This may present more of a risk for at-home testing if you need to make sure that the person hasn't squeezed their finger at all.
Quite an interesting set of problems that I'd not really considered before.
Full article: http://ajcp.oxfordjournals.org/content/144/6/885.full