Feasibility of a rapid method to evaluate platelet survival time

The purpose of this study was to evaluate the feasibility of a shorter method of performing platelet kinetic studies with respect to the conventional 8-9-day approach.

We studied 41 patients (28 women, 13 men; mean age 52 yr) with primary idiopathic thombocytopenic purpura (ITP) (n = 20), secondary ITP (n = 9), HCV associated thrombocytopenia (n = 9), splenectomy (n = 1) and hairy-cell leukemia (n = 1). The patients were in a steady-state of platelet turnover. Initial platelet counts ranged from 19 to 302 x 10(9)/liter (mean value = 83). Platelet survival times (PST) were measured from the blood radioactivity disappearance curve of 111In-oxine-labeled autologus platelets following the recommendations of the International Committee for Standardization in Haematology: blood samples were taken at 30 min and 2 and 4 hr and thereafter daily for 7 days. PST was calculated by the weighted mean method and ranged from 18 to 219 hr (mean value = 98). PST was also calculated using only the data collected at 2, 48 and 96 hr. If the radioactivity in the blood at 96 hr exceeded 10% of the 2-hr value, the additional point at 168 hr was used.

By using this reduced dataset, we obtained a correlation of r = 0.97 with the PST obtained from the whole dataset. In 24 patients, the difference was between +/- 10 hr and exceeded 1 day in only 4.

About 94% of the data may be recovered with only three or four blood samples and the duration may be shortened to 4 days in a significant proportion of patients (48% of ITP patients). This approach offers the advantages of increased patient throughput, compliance and reduced examination costs.