• N Blanco, S Leekha, L Magder, S S Jackson, P D Tamma, D Lemkin, and A D Harris.
• Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD, USA. nblanco@som.umaryland.edu.
• J Gen Intern Med. 2020 Mar 1; 35 (3): 719-723.

BackgroundThe greater the severity of illness of a patient, the more likely the patient will have a poor hospital outcome. However, hospital-wide severity of illness scores that are simple, widely available, and not diagnosis-specific are still needed. Laboratory tests could potentially be used as an alternative to estimate severity of illness.ObjectiveTo evaluate the ability of hospital laboratory tests, as measures of severity of illness, to predict in-hospital mortality among hospitalized patients, and therefore, their potential as an alternative method to severity of illness risk adjustment.Designs And PatientsA retrospective cohort study among 38,367 adult non-trauma patients admitted to the University of Maryland Medical Center between November 2015 and November 2017 was performed. Laboratory tests (hemoglobin, platelet count, white blood cell count, urea nitrogen, creatinine, glucose, sodium, potassium, and total bicarbonate (HCO3)) were included when ordered within 24 h from the time of hospital admission. A multivariable logistic regression model to predict in-hospital mortality was constructed using a section of our cohort (n = 21,003).Main MeasuresModel performance was evaluated using the c-statistic and the Hosmer-Lemeshow (HL) test. In addition, a calibration belt was constructed to determine a confidence interval around the calibration curve with the purpose of identifying ranges of miscalibration.Key ResultsPatient age and all laboratory tests predicted mortality with good discrimination (c = 0.79). Patients with abnormal HCO3 levels or leukocyte counts at admission were twice as likely to die during their hospital stay as patients with normal results. A good model calibration and fit were observed (HL = 13.9, p = 0.18).ConclusionsAdmission laboratory tests are able to predict in-hospital mortality with good accuracy, providing an objective and widely accessible approach to severity of illness risk adjustment.

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