Objectives: To investigate the use of platelet volume indices in the interpretation of thrombocytopenia in dogs with systemic disease.

Methods: Case records of 80 control dogs and 159 thrombocytopenic dogs with systemic disease were reviewed retrospectively. The relationships between mean platelet volume, platelet distribution width and platelet count in systemically well dogs were established. Knowledge of these relationships was used to interpret thrombocytopenia in terms of the underlying disease process.

Results: There was a positive relationship between platelet distribution width and mean platelet volume. Both platelet distribution width and mean platelet volume varied in a negative relationship with platelet count, which was unaffected by signalment, underlying disease, variations in haematological parameters or serum proteins.

Clinical Significance: The interpretation of mean platelet volume and platelet distribution width in dogs requires simultaneous reference to the platelet count. Platelet volume indices did not aid interpretation of thrombocytopenia in terms of underlying pathological processes in the population studied.