Inhaled Treprostinil in PH-ILD: Interpreting Claims-Based Reductions in Hospitalizations

Teja Narra

https://doi.org/10.1002/pul2.70303 

Letter

I read with interest the study by Cassady and colleagues comparing healthcare utilization among patients with pulmonary hypertension associated with interstitial lung disease (PH-ILD) who initiated inhaled treprostinil versus matched patients who remained untreated in a large US administrative claims dataset. The authors report fewer all-cause and ICU-related hospitalizations among treated patients, including a 30% decreased risk of hospitalization compared with untreated controls (relative risk 0.70; 95% CI 0.59–0.83; p < 0.01) [1].

In routine care, it helps to name what a claims-based estimate can and cannot represent. Patients who ultimately receive inhaled treprostinil are a selected subset. They must survive long enough for PH-ILD to be recognized, reach a clinician comfortable prescribing the therapy, navigate authorization, and remain stable enough to attempt inhaled titration. Selection is visible even in the matched cohorts. After matching, right heart catheterization was far more common in treated patients than in untreated patients (79% vs 16%), which suggests meaningful differences in diagnostic certainty and care pathways between groups [1].

Time-zero alignment is a second issue. In this analysis, treated patients are indexed at treprostinil initiation, whereas untreated patients are indexed at the first observed PH diagnosis. Events that occur between diagnosis and treatment start are not counted in the treated group by design. In a condition with high short-term morbidity and competing risks, this can amplify apparent benefit through immortal time bias [2]. Sensitivity analyses that treat therapy as a time-varying exposure or apply a landmark design would help bound the magnitude of this effect [2].

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