Which Observations from the Complete Blood Cell Count Predict Mortality for Hospitalized Patients?

Abel N Kho, MD, MS; Siu Hui, PhD; Joe G. Kesterson, BS; Clement J. McDonald, MD

Disclosures

Journal of Hospital Medicine. 2007;2(1):5-12. 

In This Article

Abstract and Introduction

Abstract

Background: Information on the prognostic utility of the admission complete blood count (CBC) and differential count is lacking.
Objective: To identify independent predictors of mortality from the varied number and morphology of cells in the complete blood count defined as a hemogram, automated five cell differential count and manual differential count.
Design: Retrospective cohort study and chart review.
Setting: Wishard Memorial Hospital, a large urban primary care hospital.
Patients: A total of 46,522 adult inpatients admitted over 10 years to Wishard Memorial Hospital-from January 1993 through December 2002.w
Intervention: None.
Measurements: Thirty-day mortality measured from day of admission as determined by electronic medical records and Indiana State death records.
Results: Controlling for age and sex, the multivariable regression model identified 3 strong independent predictors of 30-day mortality-nucleated red blood cells (NRBCs), burr cells, and absolute lymphocytosis-each of which was associated with a 3-fold increase in the risk of death within 30 days. The presence of nucleated RBCs was associated with a 30-day mortality rate of 25.5% across a range of diagnoses, excluding patients with sickle-cell disease and obstetric patients, for whom NRBCs were not associated with increased mortality. Having burr cells was associated with a mortality rate of 27.3% and was found most commonly in patients with renal or liver failure. Absolute lymphocytosis predicted poor outcome in patients with trauma and CNS injury.
Conclusions: Among patients admitted to Wishard Memorial Hospital, the presence of nucleated RBCs, burr cells, or absolute lymphocytosis at admission was each independently associated with a 3-fold increase in risk of death within 30 days of admission.

Introduction

The complete blood count (CBC) bundles the automated hemogram, an automated differential count of 5 types of cells, and a reflex manual differential count (when required by protocol) and is one of the most frequently ordered laboratory tests on admission to the hospital. In practice, it is a routine ingredient of all hospital admission orders-physicians order a hemogram either alone or as part of a complete blood count for 98% of our medical/ surgical admissions, and the same is true at most institutions.[1] We know that the white blood cell count and hematocrit from the automated hemogram predict disease severity and mortality risk.[2–5] For example, elevated WBC counts predict a worse prognosis in patients with cancer or coronary artery disease,[6,7] and anemia predicts increased risk of death of patients with heart failure.[8,9] Further, these two tests provide direct management guidance in common circumstances, for example, bleeding and infection.

The CBC describes the number and morphology of more than 40 cell types, from acanthocytosis to vacuolated white blood cells. Disagreement exists about the clinical significance of many of these observations.[10–13] And only a few components of the manual differential, for example, nucleated red blood cells (NRBCs) and lymphocytosis, have been quantitatively evaluated to determine their prognostic significance.[14–17] But these two observations have not been examined to determine their independent contributions to predictions of mortality when taken in conjunction with their accompanying CBC observations. Which of the numerous cell types and cell counts in the commonly ordered CBC, indicate that a patient is at high risk of death? In this article we report an inpatient study that used univariate and multivariate analyses of admission CBCs to predict 30-day mortality in order to answer that question.

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