Mean Platelet Volume is not a Useful Predictor of Mortality in Septic Shock

Introduction: Mean Platelet Volume (MPV) is a measurement that describes the average size of platelets in blood. Coagulation and platelet activation and hyperaggregation can occur in the early inflammatory phase of sepsis and septic shock. The objective of this study was to investigate the association between MPV on day 1 of development of septic shock and ICU mortality. Methods: This retrospective cohort included all patients with septic shock admitted to a 50-bed ICU between July 2005 and February 2010. Patients were treated according to sepsis management guidelines. A total of 484 septic shock patients were included. The normal range of MPV is 5.0-15.0 femtoliters (fl). We performed a mulivariate logistic regression (MLR) analysis including acute physiologic and chronic health evaluation (APACHE) II scores, sequential organ failure assessment (SOFA) scores, age, platelet count (PC) and MPV. In addition, we estimated the receiver operator characteristic (ROC) area under the curve (AUC) for MPV and mortality. Results: There were 314 survivors (65%) and 170 nonsurvivors (35%). Average APACHE II, SOFA, age, and PC were 23 (± 7), 9.8 (± 2.8), 66 (± 15) years, and 257 (± 149) respectively in survivors, versus 27 (± 9), 11.3 (± 2.9), 70 (± 14) years, and 215 (± 112) respectively in nonsurvivors. MPV was 10.5 (± 0.9) for survivors and 10.6 (± 0.9) for non-survivors. Using MLR analysis, APACHE II, SOFA, age, and low PC were all significantly associated with increased mortality : Odds ratio=1.05 (95% confidence interval, 1.02-1.08, p=0.003), OR=1.12 (95% CI, 1.03-1.22, p=0.01), OR=1.02 (95% CI, 1.01-1.03, p=0.01), and OR=1.002 (95% CI, 1.001-1.004, p=0.008), respectively. MPV was not significantly associated with mortality (OR=1.11; 95% CI, 0.77-1.62, p=0.5). Estimating the ROC AUC showed that MPV has a no discriminative power for predicting mortality (ROC AUC=0.5). Conclusions: There was no relation between mean platelet volume on day 1 of septic shock and mortality. This will need to be prospectively studied before final conclusions could be made