Peripheral Blood Myeloid/Platelet:Lymphoid Ratios Predict Mortality Risk Amongst 70,917 Emergency Medical Admissions: A Cohort Study

Abstract

Background: Historical and recent studies find that elevation in the monocyte:lymphocyte(ML), neutrophil:lymphocyte(NL) or platelet:lymphocyte(PL) ratios are associated with impaired outcomes for a variety of infectious, malignant and cardiovascular diseases. Methods: We jointly considered absolute or relative blood counts amongst 70,917 adults admitted as emergency medical admissions to two centers in Oxfordshire between 2006-2010, for predicting all-cause mortality within 28 days of admission. Peripheral blood lymphocyte, monocyte, neutrophil and platelet counts or NL, ML and PL ratios were modeled as predictors of 28-day survival in Cox-proportional hazards models adjusting for sex and age using fractional polynomials to allow for non-linear associations. Results: Blood count variables improved the predictive power of a null model including age and sex only; NL, ML and PL ratio outperformed the respective constituent measures alone. Moreover, NL, ML and PL ratios are highly correlated. Amongst the three ratios, the NL ratio was of greatest discriminatory value (100-fold bootstrapped C-index=0.76), with elevation in the NL ratio associated with elevated hazards of death across age and sex strata and regardless of intercurrent infection or of extreme values. Discussion: Myeloid or platelet to lymphoid cell ratios are predictors of mortality. The peripheral blood NL ratio is superior to other measures for predicting mortality risk in adult emergency medical admissions. Our results reconcile the pleiotropic associations of the ML, NL and PL ratios in suggesting that the activity of platelet/myeloid-biased HSC may be an inherent feature of males and females across the adult age spectrum at elevated risk of death. Funding Statement: This study was supported by the NIHR Biomedical Research Centre, Oxford. Declaration of Interests: The authors have no competing interests to declare. Ethics Approval Statement: The Infections in Oxfordshire Research Database project has Research Ethics Committee and Health Research Authority approval (14/SC/1069, ECC5-07(a)/2009).