How to Use Monocyte Distribution Width (MDW) in Your Emergency Department (ED)


In this presentation, Dr. Tobin Efferen shares the fundamentals of MDW and explains the clinical utility of incorporating the MDW biomarker as part of the CBC-diff early in ED screening to aid in identifying severity of infection and risk of sepsis.

Presenter: Tobin Efferen, MD, MS

What is MDW?

Monocyte Distribution Width (MDW) is a severity index marker that measures increased morphological variability of monocytes in response to bacteria, viral or fungal infections. MDW assists in clinical patient assessment: higher MDW values equate to higher relative risk of severe infection in adult patients.
  • MDW, exclusive to Beckman Coulter hematology analyzers, is the only regulatory-cleared hematological biomarker that helps to identify severity of infection and risk of sepsis in adult patients in the ED
  • MDW helps reduce diagnostic uncertainty, aiding clinicians in escalation or de-escalation care in patients with suspected infectious etiology
  • MDW is available early in patient assessment as a part of a CBC with Differential test, no impact to workflow

Clinical Evidence

MDW has been studied for the past decade with more than 16 peer-review publications and over 21,000+ patients1-11, confirming the robustness and reproducibility of MDW performance in different patient populations.

The clinical utility of MDW is supported by numerous peer reviewed published studies in medical journals including Chest, Critical Care Medicine and Journal of Intensive Care.

Regulatory-Cleared Indications for Use

MDW is intended for use with adult patients presenting to the emergency department for whom a white blood cell differential test has been ordered. MDW is measured from a (K2EDTA) whole-blood venous sample within 2 hours of collection. MDW results greater than 20.0, together with other laboratory findings and clinical information, aid in identifying patients with sepsis or at increased risk of developing sepsis within the first 12 hours of hospital admission.


  1. Malinovska, A et al., Monocyte distribution width as part of a broad pragmatic sepsis screen in the emergency department. JACEP Open. 2022; 3:e12679. 
  2. E. Piva et al., Monocyte Distribution Width (MDW) Parameter as a Sepsis Indicator in Intensive Care Units, Clin Chem Lab Med 2021.
  3. P. Hausfater et al., Monocyte Distribution Width (MDW) Performance as an Early Sepsis Indicator in the Emergency Department: Comparison with CRP and Procalcitonin in a Multicenter International European Prospective Study, Crit Care 2021; 25, 227.
  4. A. Woo et al., Monocyte Distribution Width Compared with C-Reactive Protein and Procalcitonin for Early Sepsis Detection in the Emergency Department, PLoS ONE 2021; 16(4): e0250101.
  5. H. Lin et al., Clinical Impact of Monocyte Distribution Width and Neutrophil-to-Lymphocyte Ratio for Distinguishing COVID-19 and Influenza from Other Upper Respiratory Tract Infections: A Pilot Study, PLoS ONE 2020 15(11): e0241262.
  6.  L. Agnello et al., Monocyte Distribution Width (MDW) as a Screening Tool for Sepsis in the Emergency Department, Clin Chem Lab Med 2020; 58(11):1951-1957. https://doi:10.1515/cclm-2020-0417
  7. G. Riva et al., Monocyte Distribution Width (MDW) as Novel Inflammatory Marker with Prognostic Significance in COVID 19 Patients, Scientific Report 2021; 11:12716.
  8. Marcos-Morales, A et al., Elevated monocyte distribution width in trauma: An early cellular biomarker of organ dysfunction, Injury 2021; S0020-1383(21):00933-00935.
  9. E. Crouser et al., Monocyte Distribution Width: A Novel Indicator of Sepsis-2 and Sepsis-3 in High-Risk Emergency Department Patients, Critical Care Med 2019; 47:1018-1025.
  10. E. Crouser et al., Improved Early Detection of Sepsis in the ED with a Novel Monocyte Distribution Width Biomarker, CHEST 2017; 152(3):518-526.
  11. A. Ognibene et al., Elevated Monocyte Distribution Width in COVID-19 Patients: The Contribution of the Novel Sepsis Indicator, Clinica Chimica Acta 2020; 509: 22-24.