Background/Purpose: Familial hypophosphatemia (FH) is most commonly due to phosphate regulating endopeptidase X-linked (PHEX) gene mutations resulting in renal phosphate wasting, which leads to rickets, osteomalacia and other musculoskeletal consequences. X-linked hypophosphatemia, the most common form of FH, may be treated with burosumab. However, the healthcare utilization and economic burden of FH among burosumab-naïve patients has not been characterized in the United States (US). This study aimed to examine healthcare utilization and costs for burosumab-naïve patients with FH, compared with demographically matched controls without FH.

Methods: Using the Merative™ MarketScan® Commercial and Medicare US administrative claims databases, patients with >1 diagnosis code for FH (ICD10:E83.31) between 1/1/2018-12/31/2021, and continuous database enrollment for 12-months pre-and post-index were identified. The index date was defined as the date of the first FH diagnosis. FH patients were demographically matched 1:3 to non-FH control patients based on age group (0-11, 12-17, 18-29, 30-39, 40-40, 50-64, 65+), sex, geographic region, payer, and index year. Healthcare utilization and costs were assessed in the 12-month post-index period and adjusted to 2021 dollars using the medical care component of the Consumer Price Index. The Charlson Comorbidity index (CCI) score was reported in the 12-month pre-index period as a measure of baseline health status. Results were reported overall and stratified by age groups.

Results: Matched burosumab-naïve FH patients (n=570) and non-FH controls (n=1,710) were 57.0% female, 53.0% with an index year in 2018-2019, and with a mean (standard deviation [SD]) age of 47.2 (19.9) and 46.2 (18.3) years (10.4%, 76.2%, and 13.5% were < 18, 18-64, and 65+ years respectively). Baseline CCI score was significantly greater among FH patients than controls (1.9 [2.6] vs. 0.2 [0.9], P< 0.001). Annual all-cause healthcare utilization was greater among FH patients compared with controls: inpatient (IP) admissions (60.4% vs. 4.3%), emergency room (ER) visits (51.6% vs. 15.7%), and outpatient (OP) pharmacy (95.8% vs. 71.1%) (all P< 0.001). FH patients also had a higher mean number of IP admissions (1.2 [1.8] vs. 0.1 [0.3]), ER visits (1.3 [2.1] vs. 0.2 [0.6]), and OP pharmacy prescriptions (36.8 [32.1] vs. 8.3 [14.8]) (all P< 0.001). Annual mean total healthcare costs were significantly higher among FH patients than controls ($118,770 [$316,629] vs. $5,627 [$18,381]), driven by greater IP costs ($67,671 [$277,681] vs. $1,526 [$12,268]), OP costs ($35,347 [$86,914] vs. $3,154 [$11,026]), and OP pharmacy costs ($15,753 [$86,994] vs. $947 [$4,379]) (all P< 0.001). Similar trends were observed among age-stratified FH patients and non-FH controls.

Conclusion: FH patients incur substantially higher healthcare utilization, costs, and comorbidity burden compared with non-FH controls.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/annual-economic-burden-for-patients-with-familial-hypophosphatemia-in-the-united-states/