Study: Fingerprick Blood Test Results Highly Variable

Results from single-drop fingerprick blood tests can be highly variable, and as many as 6-9 drops are required to achieve consistent results, according to a recent study.

While fingerprick blood tests are commonly used, few studies have examined the accuracy and reliability of these tests.
__________________________________________________________________________________________________________________________________________________________________________

RELATED CONTENT
New Blood Test Could Identify Alzheimer's Before Symptoms Emerge
Could a Common Blood Test Predict Hypertension?
__________________________________________________________________________________________________________________________________________________________________________

Researchers conducted their study in response to variation observed in a previous study of methods of anemia testing.

They drew 6 successive 20-microliter drops of blood from 11 participants, then 10 successive 10-microliter drops from 7 participants, all via fingerprick.

Using a hematology analyzer, researchers examined hemoglobin concentration, total white blood cell count, 3-part white blood cell differential, and platelet count in the first 11 participants, then used a hemoglobinometer to measure hemoglobin concentration in the 7 secondary participants.

Overall, researchers observed significant variation in platelet and white blood cell count from drop to drop.

“[I]n some donors, the hemoglobin concentration changed by more than 2 grams per deciliter in the span of 2 successive drops of blood,” they explained.

Researchers noted that by averaging test results from 6-9 drops, they were able to achieve results equivalent to venous blood tests.

“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,” they concluded.

—Michael Potts

1. Bond MM, Richards-Kortum RR. Drop-to-drop variation in the cellular components of fingerprick blood. American Journal of Clinical Pathology. 144, 885-894.

2. RICE University. Blood test results vary from drop to drop in finger prick tests [press release]. November 17, 2015. http://news.rice.edu/2015/11/17/blood-test-results-vary-from-drop-to-drop-in-finger-prick-tests/.