The Value Of The Change Of Platelet Parameters In Assessing The Severity And The Prognosis Of Patients With Severe Community-acquired Pneumonia

Objective:To observe the changes in platelet parameters,（include platelet count（PLT）,platelet distribution width（PDW）,mean platelet volume（MPV））in patients with severe community-acquired pneumonia（SCAP）,and to explore the relationship between the changes of platelet parameters and the severity and the prognosis in patients with SCAP.Methods:A retrospective study was conducted.A total of 112 cases from the patients with SCAP admitted to our hospital from June 2016 to December 2019were collected,included patients whose length of stay≥5 days and 112 patients with CAP（non-SCAP）were enrolled as the control group at the same period.The clinical data included general information and serum platelet parameters levels at initial,third,fifth days（PLT₁,MPV₁,PDW₁,PLT₃,MPV₃,PDW₃,PLT₅,MPV₅,PDW₅）and final level of platelet parameters（PLT,MPV,PDW）after admission were collected.The patients were divided into the SCAP group and the non-SCAP group according to the severity of the disease,and the general information and the initial levels of platelet parameters were compared between the two groups.Correlations between initial platelet parameters and the CRUB-65、PSI score were analyzed by Spearman correlation method.According to the 28-day outcome,the patients with SCAP were divided into survival group（n=66）and death group（n=46）,and the general information,the different time of the level of platelet parameters,the change of platelet parameters（ΔPLT,ΔMPV,ΔPDW）were compared between survival group and death group.Logistic regression was used to analyze the risk factors of prognosis for SCAP patients.The receiver operating characteristic（ROC）curve was plotted according to the change of platelet parameters to evaluate their predictive value for prognosis.Results:1.No significant difference was found in MPV₁ between SCAP group and non-SCAP group（P>0.05）.The level of PDW₁ of patients in the SCAP group was significantly higher than that in the non-SCAP group（15.6%vs.12.9%,P<0.05）,while the level of PLT₁ was lower than that in the non-SCAP group（190.5×10⁹/L vs.213.0×10⁹/L,P<0.05）.Correlation analysis results showed that PDW₁ was positively correlated with CURB-65 score and PSI score（P<0.05）,and PLT₁ was negatively correlated with PSI score（P<0.05）.2.No significant difference was found in the level of platelet parameters at initial,third day（PLT₁,MPV₁,PDW₁,PLT₃,MPV₃,PDW₃）between the survival group and death group.The level of PLT₅of patients in the death group was lower than that in the survival group（180.0×10⁹/L vs.261.5×10⁹/L,P<0.05）.No significant difference was found in the level of MPV₅,PDW₅.For the final level platelet parameters,the level of PLT of patients in death group was lower than that in survival group（163.0×10⁹/L vs.287.0×10⁹/L,P<0.05）,while level of MPV、PDW in death group was higher than that in survival group（MPV:11.2fl vs.10.2fl,P<0.05;PDW:16.3%vs.11.4%,P<0.05）.3.No significant difference was found in the changes of platelet parameters（ΔMPV₃,ΔPDW₃,ΔMPV₅,ΔPDW₅）between the death group and the survival group.The change of PLT had significant difference between death group and survival group（ΔPLT₃:-30.5×10⁹/L vs.-2.5×10⁹/L;ΔPLT₅:-20.1×109/L vs.65.9×10⁹/L;the final day ofΔPLT:-46.5×10⁹/L vs.101.0×10⁹/L;all P<0.05）.In the death group,the level of PLT was decreased obviously than the survival group.The final day ofΔMPV andΔPDW had a significant difference between the death group and the survival group（ΔMPV:1.4fl vs.0.2fl;ΔPDW:1.1%vs.-2.5%,all P<0.05）.In the death group,the level of MPV and PDW was increased obviously than the survival group.4.ΔPLT₅ and the change of final level of platelet parameters（ΔPLT,ΔMPV andΔPDW）were associated with the death of SCAP after adjusting for age and invasive mechanical ventilation（P<0.05）,and their odds ratio（OR）（95%confidence interval）were 0.995（0.991～1.000）,0.993（0.989～0.997）,1.439（1.103～1.877）,1.468（1.226～1.723）respectively.5.The area under the ROC analysis ofΔPLT₃,ΔPLT₅and final change of platelet parameters（ΔPLT,ΔMPV,ΔPDW）about the prediction of mortality were 0.657,0.713,0.767,0.730,0.798 respectively.ΔPLT combined withΔMPV orΔPDW and the combination of them,and the area under ROC analysis of them were 0.792,0.836,0.849 respectively.Conclusions:1.The initial level of PLT and PDW can reflect the severity of patients with SCAP.As the severity of the disease increased,the level of PLT decreases,while the level of PDW increases.2.Dynamically monitoring the change of platelet parameters,the continuous declining trend of PLT indicates poor prognosis for patients with SCAP,especially the change of PLT on the fifth day.The increasing trend of MPV and PDW also indicates poor prognosis for patients with SCAP,when combined with the change of PLT,MPV,PDW,it may play an important role in assessing outcome patients with SCAP.