Abstract
<p>Background: Mean platelet volume (MPV) and plateletcrit (PCT) are indices used in evaluating immune-mediated thrombocytopenia (IMT) in humans and in dogs with congenital macrothrombocytopenia. These indices may provide clinically valuable information in acquired thrombocytopenia.</p>
<p>Hypothesis/Objectives: Dogs with presumed primary IMT will have increased MPV, and therefore platelet mass (PCT)will increase faster than platelet count (PLT) during recovery.</p>
<p>Animals: Forty-nine dogs with automated PLT<30,000/lL because of presumed primary IMT and hematocrit (HCT),PCT, MPV, and platelet distribution width determined from the same complete blood count (CBC), and 46 healthy controls.</p>
<p>Methods: Case-control retrospective study; PLT, PCT, MPV, and platelet distribution width (PDW) were recorded from CBCs from 49 dogs, with 45 having data collected on the day of presentation. Fifteen were confirmed to have attained a PLT≥75,000/lL on at least 1 CBC within 15 days after admission. The PCT equivalent to a PLT of 75,000/lL(assuming an average MPV) was calculated for comparison with PLT in terms of time to achieve a threshold of platelet mass by the 2 measures.</p>
<p>Results: Mean platelet volume was higher in IMT dogs (17.3 fl) than the reference population (10.5 fl) (P<.0001).The PDW was not significantly different among the groups. The median time for PCT to reach threshold in confirmed responders was faster (3 days) compared with PLT (4 days).</p>
<p>Conclusions and Clinical Importance: Immune-mediated thrombocytopenia is characterized by increased MPV. Time to achieve a threshold PCT tended to be shorter than PLT, suggesting that PCT may be a useful platelet parameter for monitoring dogs with IMT.</p>