Abstract: Objective To explore the intrinsic connection and the clinical value of monocytes for disease courses in adult mycoplasma pneumonia. Methods A retrospective analysis of 95 patients with mycoplasma pneumonia from January 2016 to December 2018 was conducted in Department of Emergency, Xuanwu Hospital, Capital Medical University. Patients were divided into long-course group (n=71) and short-course group(n=24) based on whether disease courses were longer than 14 days. The absolute value of monocytes(MO) and thepercentage of monocytes(MO%) in blood routine were collected within 24 hours of admission. Furthermore, their correlations with disease courses were discussed. Results Baseline analysis displays that the MO, MO%, C-reactive protein (CRP),procalcitonin, red blood cell, platelet volume distribution width (PDW), average platelet volume and heart rates were lower, and the oxygen partial pressure was higher in the long-course group (P<0.05).Logistic regression showed that MO% was an independent predictor of disease duration over 14 days (P=0.003). Receiver operating characteristic (ROC) curve analysis showed that MO% had moderate predictive value for disease courses. Area under ROC curve, MO%: 0.708±0.062(P=0.002), cut-off value: 7.414 7%,sensitivity (Se) 63.38%,specificity(Sp)79.17%,positive predictive value (PV+) 90.0%, negative predictive value, (PV-) 42.22%. The area under the combined predictive ROC curve of MO% with CRP and PDW: 0.793±0.053(P=0.000), cut-off value: 7.441 4,Se 78.87%,Sp 70.83%, PV+88.89%,PV-53.13%. Conclusions MO% has clinical application value in disease-course prediction and evaluation of mycoplasma pneumonia in adults:especially combined with CRP and PDW.The smaller the MO% value, the longer the course of disease.

Key words: mycoplasma pneumonia, monocyte, course of disease, adult