Prolonged bleeding times may be evident in patients with various conditions. Analysis of platelet function can provide an insight into the cause. Platelets contain substances such as ADP, calcium, epinephrine, and serotonin which are stored in the electron dense or delta granules. Our experience has shown normal platelets to have 4-6 dense granules (Figure 1), which is supported by the literature. The prolonged bleeding times of patients who have less than the normal number of dense granules may be attributed to the lack of adequate factors that aid in the clotting process. These storage pool deficient (SPD) patients are being classified by their low dense granule count. Patients with prolonged bleeding times but normal dense granule counts may need to have their granules evaluated for size and volume (Figure 2).

Whole mounted platelets were placed in the transmission electron microscope (TEM), and negatives were obtained at a magnification of 10,200x. The typical dense granule seen in normal whole mounts is circular.