Results vary when using blood from fingerprick tests

An average of of six to nine drops was required to get the same test consistency as results from a vial of blood taken from an arm vein.
By Stephen Feller  |  Nov. 18, 2015 at 10:02 AM
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HOUSTON, Nov. 18 (UPI) -- Fingerprick blood tests spare patients the needle required for venipuncture, however research at Rice University calls into question the accuracy of using drops from a finger instead of a vial taken from the arm.

A new study, published in the American Journal of Clinical Pathology, found six to nine drops of blood have to be combined in order to get consistent results from prick tests to mitigate variations in hemoglobin, white blood cells and platelets.

The researchers suggest using care when taking fingerprick tests, and use them in the most appropirate -- or needed -- applications.

"A growing number of clinically important tests are performed using fingerprick blood, and this is especially true in low-resource settings," said Meghan Bond, a researcher at Rice University, in a press release. "It is important to understand how variations in fingerprick blood collection protocols can affect point-of-care test accuracy as well as how results might vary between different kinds of point-of-care tests that use fingerprick blood from the same patient."

Researches at Rice's Institute for Global Health Technologies are working to develop tests for anemia, platelet, and white blood cell testing in low-resource settings. Bond noticed differences between prick tests in blood analyzers the lab is testing, mounting an experiment to determine whether the discrepancies were due to the devices or differences in blood samples.

Bond drew six successive 20-microliter blood drops from 11 donors, as well as 10 successive 10-microliter drops, in order to test consistency among samples and to find out if the size of the droplet makes a difference. The droplet tests were compared to results from standard blood samples from an arm vein.

The blood drops showed significant variation from drop to drop, Bond said, such as two-gram-per-deciliter differences between two successive drops. Averaging the results of fingerprick tests give accurate results, however she said that requires at least six to nine drops in order to get consistent results.

"Fingerprick blood tests can be accurate and they are an important tool for health care providers, particularly in point-of-care and low-resource settings," Bond said. "Our results show that people need to take care to administer fingerprick tests in a way that produces accurate results because accuracy in these tests is increasingly important for diagnosing conditions like anemia, infections and sickle-cell anemia, malaria, HIV and other diseases."

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