Background: That thrombocytopenia results in increased mortality or transfusion requirements has not been confirmed by previous studies. We performed a case-control study in which 36 patients who developed severe thrombocytopenia of less than 50×109 platelets/l were carefully matched for the severity of underlying disease and other important variables.

      Results:
      Seventeen (47%) thrombocytopenic patients died, versus 10 (28%)
            matched control patients who were not thrombocytopenic.Nine pairs had a
            discordant outcome, and in eight of these pairs the thrombocytopenic patient
            died (exact binomial probability 0.037). The estimated attributable mortality
            was 19.5% (95% confidence interval 3.2⌓35.8), and the estimated odds ratio was
            2.7 (95% confidence interval 1.02⌓7.10). Thrombocytopenic patients had
            comparable values for severity of illness scores between day of admission and
            day of thrombocytopenia, in contrast with control patients who had a
            statistically significant decrease in severity of illness scores during the
            same period. Thirty (83%) of the thrombocytopenic patients required transfusion
            of blood products, versus 21 (58%) control patients (paired χ2
            test 4.92, P < 0.04). The estimated attributable transfusion
            requirement was 25% (95% confidence interval 5.4⌓44.6), and the estimated odds
            ratio was 1.52 (95 confidence interval 1.05⌓2.20).


      Conclusion:
      The present study suggests that thrombocytopenia of less than
            50 × 109 platelets/l may be a marker for more severe illness and
            increased risk of death, rather than causative, because a true causal
            relationship is not established. Thrombocytopenia also leads to an excess of
            blood product consumption.