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Drop to Drop

As ever tinier drops of blood are being used to assess people's health — especially in point-of-care assays — researchers from Rice University have found that not all drops are the same, the New York Times reports.

In a study appearing in the American Journal of Clinical Pathology, Rice's Meaghan Bond and Rebecca Richards-Kortum report on their analysis of hemoglobin concentration, total white blood cell count, three-part white blood cell differential, and platelet count from six blood drops obtained one after another from fingerpricks from 11 patients.

From this, the pair found wide variation in those measurements. As compared to successive venous-derived sample, they found greater variation among the fingerprick-derived drops. To make the fingerprick samples as accurate as the venous samples, Richards-Kortum tells the Times that they had to average the results of six to nine drops of blood.

These results, the Times notes, could influence the use of "lab in a box" or "lab on a chip" approaches being investigated for use in resource-poor regions as well as approaches like that of Theranos in wealthier areas.

"If you're going to take a fingerprick stick to get your measures, you need to be aware that you're sacrificing some accuracy," Bond adds at the Times.