Mortality Risk Prediction in Amyopathic Dermatomyositis Associated With Interstitial Lung Disease: The FLAIR Model

Abstract

Background: The prognosis of amyopathic dermatomyositis (ADM)-associated interstitial lung disease (ILD) is poor. A mortality risk score model is needed to predict survival in patients with ADM-ILD and to guide clinical treatment.

Research question: How to identify patients with ADM-ILD who are at high risk and to predict patient outcome based on a risk stratification model?

Study design and methods: We evaluated 207 patients with ADM-ILD in this prospective inception study. We used a multivariable Cox proportional hazards model to identify the independent prognostic risk factors and created a risk score model according to patient data from January 2012 to December 2016. We used the index of prediction accuracy that uses the Brier score to reflect both discrimination and calibration of the model. The model was validated in an independent group of patients from January 2017 to June 2018.

Results: We developed a combined risk score, the FLAIR score, that included the following values and scores: ferritin (<636 ng/mL, 0; ≥636 ng/mL, 2), lactate dehydrogenase (<355 U/L, 0; ≥355 U/L, 2), antimelanoma differentiation-associated gene 5 antibody (negative, 0; +, 2; ++, 3; +++, 4), high-resolution CT imaging score (<133, 0; ≥133, 3), and rapidly progressive ILD (RPILD) (non-RPILD, 0; RPILD, 2). We divided patients into three risk groups according to the FLAIR score: low, 0 to 4; medium, 5 to 9; and high, 10 to 13. In both discovery and validation cohorts, high-risk patients had significantly higher mortality rates than low- and medium-risk patients (P < .001).

Interpretation: The FLAIR risk score model could help to predict survival in patients with ADM-ILD and to guide further clinical research on risk-based treatment.

Keywords: ADM-ILD; prognosis; risk score model.