A novel, non-spirometric “BMP index” for predicting severe adverse outcomes in fibrosing interstitial lung diseases

Fibrosing interstitial lung diseases (fILDs) exhibit diverse clinical courses and prognoses, with no established biomarkers for predicting acute exacerbation (AE) and early death. This study introduces a novel composite "BMP index", integrating body mass index (BMI), mucin-1, and pentraxin 3 (PTX3) to assess AE and early death risk in fILDs. Between January, 2017, and May, 2025, we enrolled 366 patients with fILDs diagnosed, managed and followed at three hospitals in southern Taiwan. Using stratified randomization with a ratio 3:2, participants were assigned to derivation (218 patients) and validation (148 patients) cohorts. Baseline circulating mucin-1 and PTX3 levels were measured via enzyme-linked immunosorbent assay. One point was assigned for each of the three components of the BMP index: BMI < 24 kg/m², mucin-1 ≥ 2.5 ng/mL, and PTX3 ≥ 2.2 ng/mL, yielding a total score from 0 to 3. The BMP index consistently stratified risk across the derivation, validation, and combined whole cohorts, with higher scores indicating increased AE and early death risks. Sensitivity analyses and comparative performance assessments confirming its robustness and superior predictive performance compared to multiple recently reported predictors. Our findings support the BMP index as a non-spirometric, noninvasive, radiation-free tool for early clinical risk stratification in fILDs.