Illustrative example of the platelet variability index (PVI) over time in a patient referred for investigation of thrombocytopenia. At timepoint a, 2 platelet count values were available ( 3 × 109/L and 70 × 109/L) and the lowest platelet count value was 3 × 109/L; thus, the PVI was calculated by log(0.83) = -0.7. At timepoint b, the third platelet count (67 × 109/L) was added, which allowed for the measurement of platelet count fluctuation to be included into the overall PVI calculation, measured as log(0.83 × 2630.2) = 7.2. At timepoint c, the fourth platelet count was added (7 × 109/L) and the fluctuation component increased; thus, PVI at this timepoint was log(0.83 × 5892.9) = 8.0, translating to a PVI score of 5 (high likelihood of definite ITP). After timepoint d, the lowest platelet count did not change and further changes in platelet count fluctuations were relatively small; hence, the PVI value remained stable.