Background: Laboratory monitoring of the effect of low-molecular-weight heparins (LMWHs)
is generally not necessary. However, prompt evaluation of heparin inhibitory effects
(i.e., anti-Xa activity) is important in cases of life-threatening bleeding, need
for urgent surgery or acute thromboembolism under LMWH treatment. We aimed to establish
a simple and reliable point-of-care method for the detection of enoxaparin. Methods:
Eighty patients under enoxaparin therapy and ten healthy volunteers without any anticoagulant
treatment were enrolled. Simultaneous measurements of anti-Xa activity using the chromogenic
method and clotting times in the absence and presence of polybrene using viscoelastometric
assays containing Russell's viper venom (RVV-test) were performed on the ClotPro device.
Results: Among the measured and derived RVV-test parameters, the ratio of the RVV
clotting times (RVV CT) detected in the absence and presence of polybrene showed the
best statistically significant correlation with anti-Xa activity (r = 0.774, p < 0.001).
Based on ROC analysis, we designated RVV CT ratios of 1.02, 1.23 and 1.6 as the best
cut-off values for separating anti-Xa ranges below and above 0.3 and 0.6 IU/mL, respectively.
If the RVV CT ratio is below or above 1.23, the anti-Xa activity is suggested to be
below 0.6 IU/mL or above 0.3 IU/mL with high certainty, respectively. Further differentiation
is possible if the RVV CT ratio is measured below 1.02 or above 1.6. In these cases,
the measured anti-Xa values are below 0.3 IU/mL or above 0.6 IU/mL, respectively,
with high probability and good predictive values. Conclusions: Our method can provide
semiquantitative information on the effect of enoxaparin and the expected anti-Xa
activity within 10 min in real clinical situations.
