Platelet sequestration patterns and clearance rates in healthy individuals

Indium-111 platelet scintigraphy evaluates the rate of platelet clearance and the site of platelet sequestration. While the indium-111 scan is commonly used as a predictor for the success of splenectomy in immune thrombocytopenia (ITP), studies evaluating platelet sequestration in healthy adults are lacking and are warranted for a comparative standard.

We designed a prospective cohort study to determine platelet clearance and sequestration in 10 healthy adults at 2 time points (S1 and S2). Moreover, we compared the results with a retrospective ITP cohort (n = 84).

Half of the healthy individuals (5/10) at S1 and 37.5% (3/8) at S2 had a splenic sequestration pattern. The spleen: liver (S:L) ratios determined at 48 h were comparable for S1 and S2 (median S1: 1.39 and S2: 1.20, p = .29); thus, they remained stable in time. No significant difference in S:L ratios was observed between healthy adults and the ITP cohort (median: 1.30, p = .54 and p = .80). Most patients with ITP (81.0%) showed a higher clearance rate than our healthy adult cohort.

Overall, this exploratory study in healthy subjects showed that there is an individual pattern of platelet clearance and sequestration, which was reproducible over time. This study sets the stage for studies into platelet clearance mechanisms in a healthy senescent or pathological setting and applications of the indium-111 scan beyond predicting splenectomy responses in ITP.