SGEM#468: Wide Open Monocytes – Using MDW to Diagnose Sepsis
Feb 22, 2025
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Dr. Aaron Skolnick, an Assistant Professor at Mayo Clinic specializing in emergency medicine, dives into the complexities of diagnosing sepsis. He discusses the promising potential of Monocyte Distribution Width (MDW) as a rapid biomarker for early detection. Skolnick highlights the challenges of identifying sepsis due to its nonspecific symptoms and critiques existing diagnostic methodologies. The conversation also covers the biases in observational studies versus randomized control trials, and evaluates the clinical implications of MDW in emergency settings.
Monocyte distribution width (MDW) shows promise as a diagnostic tool for sepsis but requires careful clinical interpretation due to variability in accuracy.
While MDW's diagnostic accuracy is notable, it should complement existing criteria rather than replace established diagnostic workflows in sepsis assessment.
Deep dives
Importance of Early Sepsis Diagnosis
Rapid and accurate diagnosis of sepsis is essential, as early intervention can significantly lower patient mortality rates. However, diagnosing sepsis is often challenging due to its nonspecific symptoms, making timely recognition critical for patient outcomes. Traditional biomarkers such as procalcitonin and lactate have limitations, prompting the exploration of newer markers. One such promising marker is monocyte distribution width (MDW), which indicates variability in monocyte size and can be rapidly assessed as part of an automated complete blood count.
Diagnostic Accuracy of Monocyte Distribution Width
The diagnostic accuracy of MDW for early detection of sepsis was examined through a systematic review and meta-analysis involving over 9,000 patients. Findings suggested that MDW has reasonable diagnostic accuracy, specifically showing pooled sensitivities of 78.9% for sepsis 2 criteria and 84% for sepsis 3 criteria. However, these results were accompanied by wide confidence intervals and significant heterogeneity, raising concerns about the reliability of these estimates. Consequently, while MDW shows potential, its clinical utility requires cautious interpretation given the variability in accuracy across studies.
Considerations for Clinical Application
Despite the findings supporting MDW as a potential biomarker for sepsis screening, its incorporation into routine clinical practice remains premature. Limitations such as moderate sensitivity and specificity, as well as the need for external validation in varied real-world contexts, suggest that MDW should not replace existing diagnostic workflows just yet. Clinicians are advised to use their clinical judgment and experience when assessing sepsis, as established criteria can often still offer reliable guidance in many cases. Ultimately, enhancing patient-oriented outcomes requires further validation of MDW to ensure its effectiveness in clinical decision-making.
Reference: Agnello et al. Monocyte distribution width (MDW) as a screening tool for early detecting sepsis: a systematic review and meta-analysis. Clinical Chemistry and Laboratory Medicine 2022; 60(5):786-792 Clin Chem Lab Med. 2022 Date: February 21, 2025 Guest Skeptic: Dr. Aaron Skolnik is an Assistant Professor of Emergency Medicine at the Mayo Clinic Alix School […]