Assessment of whole-blood spontaneous platelet aggregation during pregnancy using an impedance particle counter.

The slide test method of Velaskar and Chitre for determining platelet aggregation in whole blood after induction of aggregation was modified for spontaneous platelet aggregation and evaluated. The reproducibility was satisfactory (CV 1-3%). The results obtained with this method and the method of Velaskar were not significantly different. The Spearman rank correlation was 0.75 (p less than 0.0001). We established reference values for the particle counter method and Velaskar's method in pregnant and non-pregnant women; no significant change in spontaneous platelet aggregation was seen throughout pregnancy. In order to estimate the clinical value of the test in pregnancy, we followed up a number of pregnant patients with primary enhanced spontaneous whole-blood platelet aggregation before and after treatment with low-dose acetylsalicylic acid. The test was found to be suited for the detection of spontaneous whole-blood platelet aggregation and for the follow-up after treatment with acetylsalicylic acid. Further studies are necessary, however, to assess the predictive value of an aberrant test result during pregnancy.