Platelet function testing at low platelet counts : When can you trust your analysis?

• Background: Although flow cytometry is often brought forward as a preferable method in the setting of thrombocytopenia, the relative effects of low sample counts on results from flow cytometry-based platelet function testing (FC-PFT) in comparison with light transmission aggregometry (LTA) and multiple electrode aggregometry (MEA) has not been reported.Objectives: To compare the effects of different sample platelet counts (10, 50, 100, and 200x10(9)L(-1)) on platelet activation measured with FC-PFT, LTA, and MEA using the same anticoagulant and agonist concentrations as for the commercial MEA test.Methods: Platelets were stimulated with two commonly used platelet agonists (ADP [6.5 mu molL(-1)] and PAR1-AP [TRAP, 32 mu molL(-1)]). The specified sample platelet counts were obtained by combining platelet-rich and platelet poor hirudinized plasma in different proportions with or without red blood cells.Results: For FC, P-selectin exposure and PAC-1 binding was reduced at 10x10(9)L(-1) after stimulation with PAR1-AP (by approximately 20% and 50%, respectively), but remained relatively unchanged when ADP was used as agonist (n=9). The platelet count-dependent effects observed with PAR1-AP were eliminated when samples were pre-incubated with apyrase, implying that reduced purinergic signaling was the main underlying factor (n=5). Both aggregometry-based PFTs showed a 50% reduction at 50x10(9)L(-1) and more than 80% reduction at 10x10(9)L(-1), irrespective of agonist used (n=7).Conclusions: Although FC-PFT is generally preferable to aggregometry-based PFTs in situations with low sample platelet counts, a careful optimization of experimental parameters is still required in order to eliminate platelet count-related effects.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Hematologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Hematology (hsv//eng)

NATURVETENSKAP  -- Kemi -- Analytisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Analytical Chemistry (hsv//eng)

Nyckelord

platelet activation

platelet aggregation

platelet count

platelet function tests

thrombocytopenia

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