Platelet count and AST can reliably predict the onset of plasma leakage in dengue, a low-cost triage tool during epidemics

Abstract

Background: Dengue is one of the most important mosquito-borne viral infections to affect humans. It is most often a self-limiting febrile illness but in some instances can progress to plasma leakage and in extreme cases culminate in death. Dengue is endemic in Sri Lanka and 2017 saw the largest outbreak on record with over 160,000 cases and over 300 deaths. Health care services reached its’ limits coping with this epidemic. The objective of this study was to identify reliable, low-cost, easily-accessible and objective predictors of Dengue hemorrhagic fever (DHF) that can be used as a triage tool in epidemic situations. Methodology/Principal findings: Serologically confirmed 350 serial adult dengue patients were included in the study. 257 (73.4%) were classified as dengue fever (DF, non leakers) and 93 (26.5%) as DHF with plasma leakage. Bedside ultrasonography was used to identify plasma leakage. Bivariate and regression analysis showed platelet count (Pearson r 0.59), and AST (r 0.27) to be significantly correlated with plasma leakage and platelet count to have a moderate predictive association (R2 0.35) with plasma leakage. Platelet count <50,000/mm3 (OR 23.7; 95% CI 12.2-45.9), AST> twice, upper limit of normal (OR 7.5; 95% CI 3.9-14.3) and ALT> twice, upper limit of normal (OR 2.4; 95%CI 1.4-3.6) increased the likelihood of DHF. In the final analysis, logistic regression identified platelet count <50,000/mm3 (OR 17.2; 95% CI 8.6-34.1) and AST>2ULN (OR 5.1, 95% CI 2.1-12.1) at time of plasma leakage as significant independent predictors of DHF. ROC curve performed for Platelet count had an AUC of .89 and at a platelet count of 50,000/mm3 predicted DHF with a sensitivity of 87% and specificity of 79%. AUC for AST was 0.72 and at 93Iu/L predicted DHF with a sensitivity of 85% and specificity of 60%. Conclusion: We have identified 2 laboratory parameters that could be used to identify plasma leakage and might be useful to stratify dengue-infected patients at risk for developing severe dengue.