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Study: Single-Drop Test Results Not Reproducible

Phlebotomists: Your job isn't in danger anytime soon! Read on...

A study recently published in the American Journal of Clinical Pathology suggests test results from a single drop of blood may not be as reliable as we think. Researchers at Rice University's department of Bioengineering collected six consecutive drops of blood into separate containers from 11 donors. Each sample on each patient was tested for hemoglobin levels, WBC counts, differentials, and platelet counts. In all draws, the first drop after the puncture was wiped away.

The drop-to-drop variation was up to three times greater for hemoglobin than for samples collected by venipuncture when repeatedly tested on the same instrument. Variability was 5.7 times greater for WBC counts, 3 times greater for lymphocyte counts, 7.7 times greater for granulocyte counts, and 4 times greater for platelets.

In a separate collection, hemoglobins were measured on each of ten successive drops of blood from seven donors using the Hemocue 201+ point-of-care (POC) hemoglobinometer. The average variability was up to 5 times higher than for venous blood.

The author recommends caution when reporting and interpreting hemoglobin and WBC results for clinical decision-making when obtained by devices that use minute quantities of blood.

Read the full study here.

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