Platelet function test and bleeding risk in patients with coronary artery disease : a case-control study

Abstract

Background Management of coronary heart disease remains a challenge even with modern advances. New anti-platelet agents which reduce thromboembolic events in patients with coronary heart disease were introduced. However, there are concerns about an increased in bleeding risk for patients taking these new anti-platelet agents. Platelet function test, such as VerifyNow, claimed to be able to predict bleeding risk. However, the evidence was limited, especially among the Asian population. This study aimed to evaluate the use of VerifyNow to assess bleeding risk. Subjects with low residual platelet reactivity, i.e. low PRU value, were hypothesized to have an increased bleeding risk.

Methods This was a case control study performed in the Princess Margaret Hospital of Hong Kong. A total of 120 subjects who were taking a P2Y12 inhibitor and had a VerifyNow test were recruited. The cases were defined as subjects with a PRU value of less than or equal to 95, a threshold for increased bleeding risk as recommended by Western studies. The controls were age matched to the cases. The primary outcome was the increase in bleeding risk associated with a low PRU value at 30 days. The secondary outcome was the increase in bleeding risk associated with a low PRU value at 1 year. The use of the percentage of platelet inhibition was also evaluated as a secondary outcome. Multivariable logistic regression was used to obtain the odds ratio of the low PRU group.

Results Bleeding events occurred more frequently in the low PRU group. At 30 days, 31.7% of subjects among the case had a bleeding event while 43.3% of the cases had a bleeding event at 1 year. The majority of these bleeding events were minor bleeding, such as easy bruising. After adjusting for confounders, there was no statistically significant increase in bleeding risk among those in the low PRU group at 30 days or 1 year. Subjects with a high percentage of platelet inhibition (>50%) was also not associated with a statistically significant increase in bleeding risk.

Conclusion A low PRU value was not associated with an increased bleeding risk at 30 days. Thus the VerifyNow test was not shown to be useful in assessing the bleeding risk of patients in an Asian population, contrary to the findings from Western literature. A possible explanation was that the VerifyNow threshold for predicting bleeding might be higher among the Asian population. The definition for low residual platelet reactivity might be different in our locality. A larger sample size might also be needed. Further studies are needed to evaluate whether a different cut off is more optimal for the Asian population.