An error in the CoaguChek S device results in prosthetic heart valve thrombosis.

The CoaguChek S device offers patients on oral anticoagulant treatment, a simple and fast method of direct monitoring of their international normalized ratio (INR). It is comparable with the glucose monitoring system, a fingerprick for a drop of capillary blood and some minutes to get the INR result for further anticoagulation monitoring. We present a case of tricuspid prosthetic valve thrombosis due to inadequate anticoagulation because of an error in the point-of-care device.