[Change of platelet parameters in septic shock patients]

To observe the changes in platelet parameters including platelet volume distribution width (PDW), platelet crit (PCT) and platelet large cell ratio (PLCR) in patients with septic shock, and to approach its predictive effect on prognosis to obtain the indexes predicting the prognosis quickly and conveniently.

A retrospective study was conducted. Data from septic shock patients admitted to Peking Union Medical College Hospital from January 1 to December 31, 2012 were collected. The patients were divided into two groups according to prognosis. The general condition, laboratory parameters, infection, acute physiology and chronic health evaluation II (APACHEII) score, and platelet parameters at 5 days after admission and 2 days before discharge from hospital, such as platelet count (PLT), Mean platelet volume (MPV), PDW, PCT and PLCR were recorded. Receiver operating characteristic curve (ROC curve) was drawn for those parameters and the area under curve was compared.

A total 124 septic shock patients were enrolled finally, 88 of the patients died and 36 remained alive. PDW and PLCR were elevated with the progress of the disease, the PLT and PCT were declined, and MPV maintained at a high level. The control group showed an opposite trend. MPV in non-survivor group was significantly higher than that in survivor group [11.2 (10.5, 12.5) fl vs. 10.3 (9.7, 11.0) fl, relative risk (RR)=3.362, P=0.009]. There was no significant difference in PLT, PDW, PCT and PLCR between non-survivor group and survivor group [PLT: 105.0 (47.5, 191.5)×10(9)/L vs. 164.0 (85.0, 236.0)×10(9)/L, RR=1.004, P=0.441; PDW: 0.14 (0.12, 0.17) vs. 0.12 (0.11, 0.13), RR=1.053, P=0.795; PCT: 0.13 (0.07, 0.21)% vs. 0.18 (0.09, 0.24)%, RR=0.234, P=0.747; PLCR: 33.7 (28.1, 42.8)% vs. 26.8 (23.2, 32.0)%, RR=0.924, P=0.324]. ROC curve showed the best cutoff value for PLT was >487.0×10(9)/L, with AUC of 0.377, sensitivity of 1.14%, specificity of 100%, diagnosis accuracy of 29.27% and Youden index of 0.011; the best cutoff value for MPV was >10.5 fl, with AUC of 0.812, sensitivity of 81.82%, specificity of 65.71%, diagnosis accuracy of 75.61% and Youden index of 0.475; the best cutoff value for PLCR was >39.3%, with AUC of 0.758, sensitivity of 48.86%, specificity of 91.43%, diagnosis accuracy of 60.98% and Youden index of 0.403;the best cutoff value for PCT was >0.33%, with AUC of 0.380, sensitivity of 7.96%, specificity of 97.14%, diagnosis accuracy of 32.52% and Youden index of 0.051; the best cutoff value for PDW was >0.12, with AUC of 0.747, sensitivity of 82.96%, specificity of 57.14%, diagnosis accuracy of 74.80% and Youden index of 0.401.

Different change trends of platelet parameters can be seen between the non-survivors and survivors of septic shock patients. If PDW, PLCR and MPV show increased trend while PLT and PCT show decreased trend, a poor prognosis maybe indicated. MPV may be most useful in prognosis forecast because of its biggest AUC.