Abstract
X-linked hypophosphatemia (XLH) is a rare, genetic, progressive, phosphate-wasting disorder that causes skeletal morbidities, stiffness, pain, and impaired physical function. This study used baseline data from the XLH Disease Monitoring Program to evaluate relationships between work productivity and patient characteristics (demographics, medical history, patient-reported, and functional outcomes) in adults with XLH. Bivariate analysis guided the selection of variables for multivariate analysis after adjustment for multicollinearity and conceptual overlap. The analysis comprised 281 subjects (75.4% female; 80.8% from USA; median age 39.2 yr); 53.4% were employed full-time and 31.3% were not employed; 15.3% were receiving disability payments; 47.0% were taking burosumab at study entry. Most employed subjects were working full-time outside the home (69.9%) and in light or sedentary roles (59.6%). In multivariate analyses, patients with fewer orthopedic surgeries (odds ratio [OR] 0.88; 95% confidence interval [CI], 0.81-0.96; p=.002) and better Patient-Reported Outcomes Measurement Information System Physical Function scores (OR 1.08; 95% CI, 1.02-1.15; p=.013) were more likely to be in full-time employment than not employed. Younger patients (OR 0.97; 95% CI, 0.94-0.99; p=.014) and those with fewer orthopedic surgeries (OR 0.83; 95% CI, 0.73-0.95; p=.008) were more likely to be in medium than light or sedentary work. Those with worse WOMAC Pain scores were more likely to be doing heavy/very heavy than light or sedentary activity (OR 1.04; 95% CI, 1.01-1.07; p=.006). Full-time employment levels are low in adults of working age with XLH, and unemployment and disability payment rates are high, suggesting that XLH has a substantial impact on work productivity. Worse physical function and a greater number of orthopedic surgeries are associated with lower work productivity. Worse pain, higher number of orthopedic surgeries, and younger age are associated with heavier work roles; however, causality was not specifically investigated.