Although the appropriate quality of samples is essential for platelet function testing, information is lacking on interference from mechanical
trauma of blood and
hemolysis on PFA-100 analyzer. Citrated blood collected from nine healthy volunteers was divided into three aliquots. The first aliquot ('A') was processed without further manipulation, whereas the second and third were subjected to mechanical
trauma by two ('aliquot B') or four passages ('aliquot C') through a very fine needle (30 gauge) to produce
hemolysis and cell
trauma mimicking poor sample collection. Samples were tested on PFA-100 and Advia 2120, and plasma then separated and tested for
lactate dehydrogenase (LDH) and
hemolysis index. Negligible
hemolysis was present in aliquot A (
hemolysis index 0.2 ± 0.1, cell-free
hemoglobin 0-0.5 g/l), whereas an increasing amount was present in aliquots B (
hemolysis index of 13.1 ± 1.8, cell-free
hemoglobin 6.0-6.5 g/l) and C (
hemolysis index 24.0 ± 1.1, cell-free
hemoglobin 11.5-12.0 g/l). Increases in LDH, and concomitant reductions in platelet and red blood cell counts were observed in aliquots B and C. In hemolyzed aliquots B, four out of nine samples yielded 'flow obstruction' with both PFA-100 agonist cartridges, whereas the closure times were dramatically prolonged in the remaining five samples. In hemolyzed aliquots C, flow obstruction was recorded in six of nine samples for
collagen and
ADP and all samples for
collagen and
epinephrine, whereas closure times of
collagen and
ADP in the remaining three samples were dramatically prolonged. Mechanical
trauma of blood causing
hemolysis makes PFA-100 testing unreliable. When flow obstructions are observed, the potential presence of
hemolysis should be investigated.