Giant Platelets Induce Double Interference in Complete Blood Count.

A 34-year-old female had a fever and respiratory infection without other clinical symptoms, and her platelet count (PLT) was only 13×109/L. Her white blood cell count (WBC) was 3.3×109/L accompanied by abnormal flags from the automatic cell counter; however, giant platelets were observed on a peripheral blood smear, and leukocytes were barely found, which varied from the results of the automatic cell analyzer. Using the traditional dilution method, the PLT was corrected to 30×109/L, and the WBC was corrected to 1.4×109/L by direct microscope count, reaching almost twice the difference of values from the automatic cell analyzer. In this patient, giant platelets simultaneously caused a false increase in the WBC and a false decrease in PLT. The most reliable way to solve this rare situation relies on the dilution method, although this method is no longer favored by laboratories today.