Red cell distribution width: a novel and accessible predictor for immune checkpoint inhibitor-associated...

Immune checkpoint inhibitor (ICI)-associated myocarditis is a rare but potentially fatal immune-related adverse event characterized by high mortality and the absence of specific diagnostic biomarkers. Red blood cell distribution width (RDW), a routine hematologic parameter reflecting erythrocyte volume heterogeneity, has been linked to cardiovascular and inflammatory disease outcomes. However, its diagnostic relevance in ICI-associated myocarditis remains unclear.

A single-center retrospective study was conducted from January 2020 to January 2024, including 51 patients with PD-1 inhibitor-associated myocarditis (case group), 58 patients with viral myocarditis (Control 1), and 50 anti-PD-1-treated patients without myocarditis (Control 2). Clinical and laboratory data, including RDW and troponin T (TnT), were analyzed. Statistical tests included the Kolmogorov-Smirnov test, one-way ANOVA, logistic regression, and receiver operating characteristic (ROC) curve analysis.

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, with a survival rate of 33%. RDW was significantly elevated in the case group compared with 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 demonstrated that RDW achieved an area under the curve (AUC) of 0.8882 (cut-off = 14.65; sensitivity 85.6%, specificity 90.5%), which was comparable to TnT (AUC = 0.9102).

RDW, an easily obtainable routine laboratory parameter, is independently associated with ICI-associated myocarditis and shows high and comparable diagnostic accuracy relative to TnT. RDW may serve as a practical, noninvasive, complementary auxiliary indicator for early screening and risk stratification of ICI-associated myocarditis.