Impact of changes in haematocrit level and platelet count on thromboelastometry parameters.
BACKGROUND
To what extent haematocrit levels (Hct) and platelet counts (PLT) influence the measurement of parameters of thromboelastometry when assessed with the ROTEM® device is unclear. We investigated to what extent thromboelastometry measurements depend on Hct and PLT.


METHODS
Whole blood samples were taken for in-vitro preparations of mixtures with three different levels of PLT and a varying Hct. Maximum clot firmness (MCF), clotting time (CT), clot formation time (CFT) and alpha angle (α) for INTEM, EXTEM, FIBTEM and APTEM was recorded.


RESULTS
Measurements depended substantially on Hct and PLT. MCF readings were systematically lower with increasing Hct (0.2 vs. 0.4: -7.8 (-8.3 to -7.2); p<0.001, 0.2 vs. 0.55: -14.5 (-17.3 to -14.3); p<0.001) but higher with increasing PLT (50 vs. 125×10(9)/l: 8.2 (4.2 to 12.3); p=0.005, 50 vs. 250×10(9)/l: 12.0 (7.2 to 16.8); p=0.002). CT readings were systematically higher with increasing Hct (0.2 vs. 0.4: 9.2 (6.2 to 12.1); p=0.001, 0.2 vs. 0.55: 38.2 (21.5 to 54.9); p=0.003) while increasing PLT had no influence. CFT readings were also systematically higher with increasing Hct (0.2 vs. 0.4: 83.8 (40.2 to 127.6); p=0.006, 0.2 vs. 0.55: 226.2 (110.7 to 341.7); p=0.006) but systematically lower with increasing PLT (50 vs. 125×10(9)/l: -144.0 (-272.3 to -15.6); p=0.036, 50 vs. 250×10(9)/l: -189.2 (-330.4 to -48.0); p=0.02); readings of the alpha angle showed a similar pattern.


CONCLUSIONS
Our results suggest that readings of thromboelastometry parameters need to be adjusted by Hct and PLT to avoid potential confounding and miss-interpretations in clinical practice.
Division of Hematology and Central Haematology Laboratory, Luzerner Kantonsspital, CH-6000 Lucerne 16, Switzerland. michael.nagler@insel.ch
Michael
M
Nagler
Silvio
S
Kathriner
Lucas M
LM
Bachmann
Walter A
WA
Wuillemin
D001777:Blood Coagulation; D006400:Hematocrit / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D010976:Platelet Count / Q000295:instrumentation / Q000379:methods*; D012107:Research Design; D013916:Thrombelastography / Q000295:instrumentation* / Q000379:methods*