Objective:

To investigate the role of red blood cell distribution width (RDW) in immune checkpoint inhibitor (ICI)-associated myocarditis and its potential as a diagnostic indicator.

Approach:

• Study Design: A single-center retrospective study was conducted from January 2020 to January 2024, including 51 patients with PD-1 inhibitor-associated myocarditis, 58 patients with viral myocarditis, and 50 anti-PD-1-treated patients without myocarditis.
• Data Analysis: Clinical and laboratory data, including RDW and troponin T (TnT), were analyzed using statistical tests such as one-way ANOVA and ROC curve analysis.

Key Findings:

• RDW was significantly elevated in the ICI-associated myocarditis group compared to both control groups (P < 0.05).
• Multivariate logistic regression identified RDW (OR = 3.78) and ln(TnT) (OR = 12.12) as independent factors associated with ICI-associated myocarditis (P < 0.05).
• ROC analysis showed RDW had an AUC of 0.8882 (cut-off = 14.65; sensitivity 85.6%, specificity 90.5%), comparable to TnT (AUC = 0.9102).
• The mean onset time after PD-1 inhibition therapy was 153.5 ± 184.5 days, and the mean hospitalization period was 13.6 ± 17.5 days.

Interpretation:

Limitations:

• The study is retrospective and conducted at a single center, which may limit generalizability.
• The diagnostic criteria for ICI-associated myocarditis are not standardized, leading to potential subjectivity in diagnosis.

Conclusion:

RDW may serve as a practical, noninvasive, complementary auxiliary indicator for early screening and risk stratification of ICI-associated myocarditis.