A method for enumerating platelets within a blood sample is provided. The method includes the steps of: 1) depositing the sample into a sample container having an analysis chamber adapted to quiescently hold the sample for analysis, and an amount of colorant that platelets absorb and which fluoresces upon exposure to one or more predetermined first wavelengths of light; 2) imaging at least a portion of the sample disposed in the analysis chamber, including producing image signals indicative of fluorescent emissions from the platelets illuminated by first wavelengths of light; 3) identifying the platelets using the image signals; and 4) enumerating individual platelets and clumped platelets within the sample using one or more of fluorescent emissions, area, shape, and granularity.