PS1289 THE ATYPICAL LYMPHOCYTE COUNT: A NOVEL PREDICTIVE FACTOR FOR SEVERE DENGUE INFECTION

Abstract

Background:Dengue haemorrhagic fever (DHF) and Dengue Shock Syndrome (DSS) are life threatening complications of DI which occur in a minority of patients. The early identification of these individuals is critical to guide clinical management. There is currently no validated laboratory test which can predict severe complications of DI. The Atypical lymphocyte count (ALC) is a research parameter generated on Sysmex FBC analysers which has been correlated with the presence of circulating atypical lymphocytes (AL). Pilot studies have suggested that the presence of AL may be associated with severe DI.Aims:We evaluated the utility of the ALC as a predictive factor for severe dengue related thrombocytopaenia as well as DHF and DSS.Methods:We prospectively collected data on patients admitted to Nawaloka Hospital Sri Lanka (NH) with DI between December 2016 and August 2018. DI was diagnosed based on a positive Non‐structural antigen 1 or dengue IgM antibody. ALC data were extracted from the Sysmex XS500i automated FBC analyzer from day of admission to day seven. Clinical data was recorded from medical records and the computerized data base maintained by NH. Statistical analyses were performed using SPSS version 20.Results:201 patients were included in the study. DSS and DHF occurred in 6.5% (n = 13) and 6% (n = 12) of patients respectively. Patients with DHF and DSS as well as those with low Glasgow Coma Scale and respiratory compromise had a higher mean ALC on each day of FBC assessment compared to those without these complications. We detected a statistically significant negative correlation between the ALC on admission and platelet count on days five to seven (the period during which nadir thrombocytopaenia is expected in DI). [Spearmen's correlation; Day 5:‐0.485, Day 6:‐0.428, and Day 7:‐0.344] (P = 0.001) We performed Receiver Operator Curve (ROC) analysis to determine the predictive value of an admission ALC more than 0.5x 103/L for severe thrombocytopaenia (defined as a platelet count less than 50 x 109/l) on day five. We found that this ALC cut off had 90% sensitivity and 70% specificity for severe thrombocytopaenia on day 5. The positive and negative predictive values were 74.4% and 91.2% respectively. We also showed that patients with cardiac and abdominal ultrasonographic abnormalities had a higher mean ALC.Summary/Conclusion:We propose that an admission ALC of greater than 0.5 x 103/L has a strong predictive value for severe thrombocytopaenia on days five to seven of DI. Our data also suggest that a higher ALC on admission maybe predictive for severe DI. ALC on admission maybe a valuable modality for early identification of patients at risk of severe dengue related complications.image