Platelet reactivity index

The platelet reactivity index according to Grotemeyer is a method for measuring platelet function. This test procedure is based on the observation that in vivo the formation of platelet aggregates is activated to varying degrees. The resulting "microwhite clots" are normally eliminated. The extent to which these microaggregates are formed is a measure of thrombophilia caused by platelets.

Monitoring of platelet function-inhibiting drugs, especially predictive for the assessment of the therapeutic efficiency of acetylsalicylic acid. One advantage is that the ASA non-responders and ASA responders can be clearly distinguished from each other.

The principle of the method is that in one syringe blood with EDTA and a phosphate buffer solution and in a second syringe EDTA + formalin in a buffer are taken and mixed. 30 minutes after blood collection, the platelet count in the respective samples is determined. The platelets present in vivo or originating from aggregates dissolved by ethylenediaminetetraacetic acid are recorded. The aggregates are immediately fixed in the sample with formalin EDTA. By comparing the EDTA with the EDTA formalin blood samples it can be determined how many aggregates are present. In healthy persons the deviation is less than 5%. If the deviation is > 20%, the measurement cannot be used. The measurement results are expressed by a quotient. The number of platelets in the EDTA solution (numerator) is divided by the number of platelets in EDTA formaldehyde times the factor K (denominator). K is used here as a correction factor, which represents the number of erythrocytes in the EDTA formaldehyde solution divided by the erythrocytes in the pure EDTA solution.
A platelet reactivity index higher than 1.05 is considered suspicious. Above 1.2 it is certainly pathological.

1. HA Neumann (2014) The coagulation system. ABW-Science Publishing House GmbH Berlin.