Significance of early lymphocyte-platelets ratio on the prognosis of patients with extensive burns

Abstract

Objective: To analyze the changing trend and characteristics of lymphocyte-platelets ratio (LPR) of early stage in patients with extensive burns, and to explore the prognostic significance of LPR. Methods: A retrospective case series study was conducted. From January 2008 to December 2018, 244 patients with extensive burns were admitted to the First Affiliated Hospital of Naval Medical University, including 181 males and 63 females, aged (44±16) years. The total burned area of patients was 60.0% (42.0%, 85.0%) total body surface area. Platelet and lymphocyte test results of patients were collected on the 1st, 2nd and 3rd day after admission, and LPR of patients was calculated to analyze the changing trend of the three days after admission. Univariate and multivariate logistic regression analysis were conducted to investigate the risk factors or independent risk factors for death of patients, including age, sex, total burn area, area of full-thickness burns and above, inhalation injury, and LPR. According to the 1st day's LPR after admission of patients, the receiver operating characteristic (ROC) curve predicting death of patients was drawn to find the optimal value of LPR. Patients were divided into high LPR group (n=136) and low LPR group (n=108) based on the optimal value of LPR, and the clinical data of total burn area, area of full-thickness burns and above, inhalation injury, tracheotomy, offline time of patients within 28 days, and mortality in the 2 groups were compared. The surviving curve of patients was drawn by Kaplan-Meier method to predict the difference of the 90-day survival rate between the two groups of patients. Data were statistically analyzed with Student's t test, Mann-Whitney U test, and chi-square test. Results: Within 3 days of admission, the LPR of patients showed a time-dependent upward trend. LPR of patients on the 2nd and 3rd day after admission was 8.6 (5.3, 14.4) and 8.6 (4.9, 13.7), respectively, which were significantly higher than the 1st day's 6.3 (4.2, 9.8), with Z values of -4.25 and -3.43, respectively, P<0.01. Univariate logistic regression analysis showed that age, total burn area, area of full-thickness burns and above, inhalation injury, and LPR were all risk factors for death of patients (with odds ratios of 1.03, 1.73, 1.31, 4.74, and 3.11, respectively, 95% confidence intervals of 1.01-1.06, 1.40-2.13, 1.21-1.42, 1.62-13.86, and 1.41-6.88, respectively, P<0.01). Multivariate logistic regression analysis showed that age, area of full-thickness burns and above, and LPR were independent risk factors for death of patients (with odds ratios of 1.06, 1.36, and 2.85, respectively, 95% confidence intervals of 1.03-1.09, 1.19-1.55, 1.02-7.97, P<0.05 or P<0.01). The area under ROC curve of the 1st day's LPR, predicting death of patients, was 0.61 (with 95% confidence interval of 0.51-0.71, P<0.05), and the optimal predicted value was 5.8 with corresponding sensitivity of 77% and specificity of 52% respectively. The total burn area, area of full-thickness burns and above, rates of incidence of inhalation injury, tracheotomy, and mortality of patients in high LPR group were significantly higher than those in low LPR group (with Z values of -3.06 and -3.19, χ2 values of 5.42, 11.64, and 8.45, respectively, P<0.05 or P<0.01). The offline time of patients within 28 days in high LPR group was significantly shorter than that in low LPR group (Z=-2.98, P<0.01). Kaplan-Meier survival analysis showed that the 90-day survival rate of admission of patients in low LPR group was significantly higher than that of patients in high LPR group (χ2=8.24, P<0.01). Conclusions: The early LPR of patients with extensive burns showed a time-dependent upward trend. The LPR on the first day after admission that is closely correlated with total burn area, area of full-thickness and deeper burns, inhalation injury, tracheotomy, and mortality of patients, is an independent risk factor for the prognosis of patients with extensive burns. The first day's LPR after admission is significantly correlated with the 90-day survival rate of patients, which can be used as an evaluation index for the severity of extensive burns.