Accurate platelet enumeration is critical for optimal treatment of patients with platelet and bleeding disorders, leukemias, and other neoplasias. The majority of automated hematology analyzers count platelets by size differentiation alone, which may result in falsely elevated platelet counts for samples containing interfering particles such as RBC fragments, microcytes, and cell debris. Most analyzers flag questionable platelet counts, necessitating review of results with confirmation by an alternative method, thus increasing the cost of performing platelet counts and delaying results. We studied the effect of a new platelet analysis method, based on measurement of size and refractive index, on the laboratory review rate for platelet counting. We demonstrated that this method yields higher accuracy for platelet counts in samples with interferences, especially for platelet counts less than 50 x 10(3)/microL (< 50 x 10(9)/L). As a result of the 2-dimensional analysis, the review rate for platelet counts was reduced by 65% in our institution, resulting in substantial savings.