Clinician Introduction to MDW

In this presentation, Melissa Naiman, PhD, EMT-B shares the fundamentals of Monocyte Distribution Width (MDW) and explains the clinical utility of incorporating the MDW biomarker as part of the complete blood count with differential (CBC-diff) early in emergency department (ED) screening to aid in identifying severity of infection and risk of sepsis.


Presenter: Melissa Naiman, PhD, EMT-B

What is 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—over the established cutoff point—equate to higher relative risk of severe infection in adult patients.

  • MDW, exclusive to DxH 900 and 690T 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-diff test with no impact to workflow

Clinical Evidence

MDW has been studied in over 30,000 patients, confirming the robustness and reproducibility of MDW performance.

The clinical utility of MDW is supported by over 60 peer reviewed published studies in medical journals including ChestCritical Care MedicineClinical Chemica ActaCureusJournal of Intensive CareInfectionPLoS One, and BMC Infectious Disease.

MDW Levels 

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 whole-blood venous sample within 2 hours of collection. MDW results greater than 20.0 (K2EDTA) or 21.5 (K3EDTA), 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.

Review peer reviewed studies

1. Crouser ED, Parrillo JE, Seymour C, et al. Improved Early Detection of Sepsis in the ED with a Novel Monocyte Distribution Width Biomarker. Chest. 2017;152(3):518-526. doi:10.1016/j.chest.2017.05.039

2. Crouser ED, Parrillo JE, Seymour CW, et al. Monocyte Distribution Width: A Novel Indicator of Sepsis-2 and Sepsis-3 in High-Risk Emergency Department Patients. Crit Care Med. 2019;47(8):1018-1025. doi:10.1097/CCM.0000000000003799

3. Polilli E, Sozio F, Frattari A, et al. Comparison of Monocyte Distribution Width (MDW) and Procalcitonin for Early Recognition of Sepsis. PLoS ONE. 2020;15(1):e0227300. doi:10.1371/journal.pone.0227300

4. Crouser ED, Parrillo JE, Martin GS, et al. Monocyte Distribution Width Enhances Early Sepsis Detection in the Emergency Department Beyond SIRS and qSOFA. J Intensive Care. 2020;8:33. doi:10.1186/s40560-020-00446-3

5. Woo A la, Oh DK, Park C-J, Hong S-B. Monocyte Distribution Width Compared with C-reactive Protein and Procalcitonin for Early Sepsis Detection in the Emergency Department. PLoS ONE. 2021;16(4):e0250101. doi:10.1371/journal.pone.0250101

6. Hausfater P, Robert Boter N, Morales Indiano C, 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(1):227. doi:10.1186/s13054-021-03622-5

7. Hou S-K, Lin H-A, Chen S-C, Lin C-F, Lin S-F. Monocyte Distribution Width, Neutrophil-to-Lymphocyte Ratio, and Platelet-to-Lymphocyte Ratio Improves Early Prediction for Sepsis at the Emergency. J Pers Med. 2021;11(8). doi:10.3390/jpm11080732

8. Li C-H, Seak C-J, Chaou C-H, et al. Comparison of the Diagnostic Accuracy of Monocyte Distribution Width and Procalcitonin in Sepsis Cases in the Emergency Department: A Prospective Cohort Study. BMC Infect Dis. 2022;22(1):26. doi:10.1186/s12879-021-06999-4

9. Poz D, Crobu D, Sukhacheva E, Rocchi MBL, Anelli MC, Curcio F. Monocyte Distribution Width (MDW): A Useful Biomarker to Improve Sepsis Management in Emergency Department. Clin Chem Lab Med. 2022;60(3):433-440. doi:10.1515/cclm-2021-0875

10. Yu S, Song SA, Jun KR, Park HY, Lee JN. Clinical Performance of Monocyte Distribution Width for Early Detection of Sepsis in Emergency Department Patients: A Prospective Study. Ann Lab Med. 2022;42(2):286-289. doi:10.3343/alm.2022.42.2.286

11. Laínez Martínez S, González Del Castillo J. Usefulness of Monocyte Distribution Width (MDW) as a Sepsis Biomarker. Rev Esp Quimioter. 2022;35 Suppl 1(Suppl 1):2-5. doi:10.37201/req/s01.01.2022

12. Hou S-K, Lin H-A, Tsai H-W, Lin C-F, Lin S-F. Monocyte Distribution Width in Children with Systemic Inflammatory Response: Retrospective Cohort Examining Association with Early Sepsis. Pediatr Crit Care Med. 2022;23(9):698-707. doi:10.1097/PCC.0000000000003019

13. Ognibene A, Lorubbio M, Montemerani S, et al. Monocyte Distribution Width and the Fighting Action to Neutralize Sepsis (FANS) Score for Sepsis Prediction in Emergency Department. Clin Chim Acta. 2022;534:65-70. doi:10.1016/j.cca.2022.07.007

14. Singla N, Jandial A, Sharma N, Sharma N, Bhatia M, Behera A. Monocyte Distribution Width (MDW) as an Early Investigational Marker for the Diagnosis of Sepsis in an Emergency Department of a Tertiary Care Hospital in North India. Cureus. 2022;14(10):e30302. doi:10.7759/cureus.30302

15. Polilli E, Di Iorio G, Silveri C, et al. Monocyte Distribution Width as a Predictor of Community Acquired Sepsis in Patients Prospectively Enrolled at the Emergency Department. BMC Infect Dis. 2022;22(1):849. doi:10.1186/s12879-022-07803-7

16. Jo SJ, Kim SW, Choi J-H, Choi SP, Lee J, Lim J. Monocyte Distribution Width (MDW) as a Useful Indicator for Early Screening of Sepsis and Discriminating False Positive Blood Cultures. PLoS ONE. 2022;17(12):e0279374. doi:10.1371/journal.pone.0279374

17. Lin S-F, Lin H-A, Pan Y-H, Hou S-K. A Novel Scoring System Combining Modified Early Warning Score with Biomarkers of Monocyte Distribution Width, White Blood Cell Counts, and Neutrophil-to-Lymphocyte Ratio to Improve Early Sepsis Prediction in Older Adults. Clin Chem Lab Med. 2023;61(1):162-172. doi:10.1515/cclm-2022-0656

18. Ciaccio AM, Agnello L, Sasso BL, et al. Monocyte Distribution Width (MDW) as a Biomarker of Sepsis: An Evidenced-based Laboratory Medicine Approach. Clin Chim Acta. 2023;540:117214. doi:10.1016/j.cca.2022.117214

19. Cusinato M, Sivayoham N, Planche T. Sensitivity and Specificity of Monocyte Distribution Width (MDW) in Detecting Patients with Infection and Sepsis in Patients on Sepsis Pathway in the Emergency Department. Infection. 2023;51(3):715-727. doi:10.1007/s15010-022-01956-y

20. Encabo M, Hernández-Álvarez E, Oteo D, et al. Monocyte Distribution Width (MDW) as an Infection Indicator in Severe Patients Attending in the Emergency Department: A Pilot Study. Rev Esp Quimioter. 2023;36(3):267-274. doi:10.37201/req/108.2022

21. Eisinger GJ, Osman W, Prather ER, et al. Inflammasome Activation in an In Vitro Sepsis Model Recapitulates Increased Monocyte Distribution Width Seen in Patients with Sepsis. Crit Care Explor. 2022;4(2):e0631. doi:10.1097/CCE.0000000000000631