Anchoring patient reported outcomes (PROs) to percent functional vital capacity (%pFVC) to predict need for ventilatory support in DMD patients.


Translational Research

Poster Number: S64


Jared Fong, MD, UC Davis, Walk4Me Research Group, PhD MPH, University of California, Davis, CINRG DNHS Investigators, International

Mortality in Duchenne Muscular Dystrophy (DMD) often occurs due to lung related complications with higher risks in patients whose functional vital capacity (FVC) is 1 L or percent predicted FVC (%pFVC)<50 with a hazard ratio of 4.1. Non-ambulatory patients have an average %pFVC of 61.8 with a loss of 5-9% annually. Guidelines recommend non-invasive ventilation with %pFVC<50% and continuous ventilation at %pFVC<30%. Correlation of Brooke Upper Extremity Scale Scores and percent %pFVC make it useful for anticipating need for ventilatory support. Similar use of patient-reported outcomes (PRO) would provide clinicians with remotely administered tools. Current PRO proxy assessments of pulmonary function consist primarily of cognitive questions related to fatigue, sleep, and headache. We expand PRO evaluation of pulmonary function to include upper extremity and transfer ability question items. Methods We examined %pFVC and Pediatric Orthopedic Data Collection Instrument (PODCI) PRO responses from 440 participants from the CINRG Duchenne Natural History Study using correlation, regression and factor analysis identify PRO question items that correlate with %pFVC. Results Seventeen PODCI items showed moderate to strong correlation (r > 0.5) with %pFVC. Factor analysis confirmed unidimensionality of items that addressed upper extremity function and transfer ability. A composite score of those items showed each point decrease represents a drop in %pFVC of 0.75 (%pFVC = -0.75x + 98.5) on average. The score predicted %pFVC at <50% and <30% with an accuracy of 90% and 87%, respectively. Questions were sensitive across stages of DMD progression based on Brooke and disease milestone scales. Use of a fork and spoon was found to be the only question sensitive to %pFVC less than 30%. Conclusions A subset of upper extremity function, transfer and mobility questions from PODCI are useful as remote tools when screening DMD patients for possible need for ventilatory support.