The Prevalence, Incidence, Mortality & Costs of RA-Related ILD

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Interstitial lung disease (ILD) can be associated with rheumatoid arthritis (RA) with significant morbidity and mortality. An article in The Journal of Rheumatology focused on calculating the prevalence, incidence, mortality and costs to the healthcare system of RA-related ILD (RA-ILD).¹

“RA is the most common of connective tissue diseases encountered by rheuma­tologists—affecting about 1% of the adult population—and ILD is a known common manifestation,” says author Aryeh Fischer, MD, associate professor of medicine at the University of Colorado School of Medicine, Aurora. “We thought it would be important to learn about prevalence of ILD in RA and get a better sense of its economic burden.”

Insurance Databases Used

Dr. Fischer and others undertook a retrospective analysis of Truven Health MarketScan Commercial and Supplemental insurance databases from 2003–2014. These have more than 150 million covered lives across all geographic regions of the U.S. and include a variety of plan types. The researchers also included the Social Security Administration death database.

Patients were identified as potential RA-ILD cases based on data from medical claims, such as respiratory disease-related International Classification of Diseases, ninth edition, Clinical Modification (ICD-9-CM) codes. The date of the earliest claim was defined as the index date.

Cost data were obtained from patients who were continuously enrolled for 12 months after the index date. Healthcare use and costs were measured over a five-year term for those patients with 60 months of continuous enrollment. There were no continuous enrollment criteria for mortality.

Outcomes

Outcomes measured included one-year prevalence and incidence of RA-ILD in the general enrollee population. They also measured all-cause and respiratory-related healthcare costs reported in 2014 U.S. dollars. Finally, the researchers included all-cause survival for a subset of newly diagnosed patients for whom vital statistic information was available.

During the 10-year study, the number of patients meeting the criteria for inclusion ranged from 892 to 3,232 patients per year. Prevalence of RA-ILD varied across the 10-year period between 3.2 (95% confidence interval [CI]; 3.0–3.4) and 6.0 cases per 100,000 people (95% CI; 5.7–6.2). Incidence rates ranged from 2.7 (95% CI; 2.5–2.9) to 3.8 (95% CI; 3.5–4.0) per 100,000 people.

Prevalence Decreasing/Incidence Stable

Over time prevalence appeared to be slowly increasing while incidence remained relatively stable. The increased prevalence suggested to the researchers an increase in duration of RA-ILD, which they attributed to improved survival. They also noted that it could mean newer therapies are more effective and/or increased disease awareness has led to patients being diagnosed earlier in the course of the disease.

There were 750 patients with five years of follow-up data. During that time, 72% of participants had an inpatient admission and 76% were seen in an emergency department. Mean total five-year costs were $173,405 per patient (standard deviation [SD] $158,837). Annual per-patient costs were highest in years 1 and 5. Five years following the initial diagnosis, 35.9% of patients were still alive.

“The vast majority of patients (over 70%) had evidence of hospitalization and [emergency department] visits over a five-year period. We also found the disease is costly to the healthcare system,” says Karina Raimundo, MS, another author and principal health economist for Genentech. “More importantly, in our study we found the median survival from first evidence of evidence of diagnosis was 7.8 years. By comparison, a 65-year-old (the mean age of RA-ILD patients in the study) in the United States is expected to live another 19 years.”