Thrombocytopenia in critically ill surgical patients: a case-control
		  study evaluating attributable mortality and transfusion requirements
BackgroundThat thrombocytopenia results in increased mortality ortransfusion requirements has not been confirmed by previous studies. Weperformed a case-control study in which 36 patients who developed severethrombocytopenia of less than 50×109 platelets/l were carefullymatched for the severity of underlying disease and other importantvariables.ResultsSeventeen (47%) thrombocytopenic patients died, versus 10 (28%)matched control patients who were not thrombocytopenic.Nine pairs had adiscordant outcome, and in eight of these pairs the thrombocytopenic patientdied (exact binomial probability 0.037). The estimated attributable mortalitywas 19.5% (95% confidence interval 3.2–35.8), and the estimated odds ratio was2.7 (95% confidence interval 1.02–7.10). Thrombocytopenic patients hadcomparable values for severity of illness scores between day of admission andday of thrombocytopenia, in contrast with control patients who had astatistically significant decrease in severity of illness scores during thesame period. Thirty (83%) of the thrombocytopenic patients required transfusionof blood products, versus 21 (58%) control patients (paired χ2test 4.92, P < 0.04). The estimated attributable transfusionrequirement was 25% (95% confidence interval 5.4–44.6), and the estimated oddsratio was 1.52 (95 confidence interval 1.05–2.20).ConclusionThe present study suggests that thrombocytopenia of less than50 × 109 platelets/l may be a marker for more severe illness andincreased risk of death, rather than causative, because a true causalrelationship is not established. Thrombocytopenia also leads to an excess ofblood product consumption.