Key result
Flow cytometry provided reliable platelet function assessment at platelet counts >30 x10^9/L, whereas impedance aggregometry and in-vitro bleeding time required counts >100 x10^9/L for valid results.
Why the study?
Point-of-care platelet function tests are prone to assess platelet function incorrectly at low platelet counts.
What is the minimum platelet count required for valid results in point-of-care platelet function tests compared to flow cytometry?
Observational (n=10)
No
What is the minimum platelet count required for valid results in point-of-care platelet function tests compared to flow cytometry?
p-value: p=<0.05
Point-of-care platelet function tests are unreliable at platelet counts below 100 x10^9/L, whereas flow cytometry remains accurate down to 30 x10^9/L.
Caution against POC platelet tests below 100 x10^9/L; hypothesis-generating for flow cytometry in thrombocytopenia.
Point-of-care (POC) platelet function tests are faster and easier to perform than in-depth assessment by flow cytometry. At low platelet counts, however, POC tests are prone to assess platelet function incorrectly. Lower limits of platelet count required to obtain valid test results were defined and a testing method to facilitate comparability between different tests was established. We assessed platelet function in whole blood samples of healthy volunteers at decreasing platelet counts (> 100, 80-100, 50-80, 30-50 and < 30 x109/L) using two POC tests: impedance aggregometry and in-vitro bleeding time. Flow cytometry served as the gold standard. The number of platelets needed to reach 50% of the maximum function (ED50) and the lower reference limit (EDref) were calculated to define limits of test validity. The minimal platelet count required for reliable test results was 100 x109/L for impedance aggregometry and in-vitro bleeding time but only 30 x109/L for flow cytometry. Comparison of ED50 and EDref showed significantly lower values for flow cytometry than either POC test (P value < 0.05) but no difference between POC tests nor between the used platelet agonists within a test method. Calculating the ED50 and EDref provides an effective way to compare values from different platelet function assays. Flow cytometry enables correct platelet function testing as long as platelet count is > 30 x109/L whereas impedance aggregometry and in-vitro bleeding time are inconsistent unless platelet count is > 100 x109/L.
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Quehenberger et al. (2022) conducted an observational in Healthy volunteers (simulated thrombocytopenia) (n=10). Point-of-care platelet function tests (Impedance aggregometry and in-vitro bleeding time) vs. Flow cytometry was evaluated on Minimum platelet count required for valid test results (ED50 and EDref) (p=<0.05). Flow cytometry provided reliable platelet function assessment at platelet counts >30 x10^9/L, whereas impedance aggregometry and in-vitro bleeding time required counts >100 x10^9/L for valid results.
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