Clubbing in patients with fibrotic interstitial lung diseases

Abstract

Background: Clubbing is considered typical in idiopathic pulmonary fibrosis (IPF), but is also seen in other fibrotic interstitial lung diseases (FILDs). Little is known about the exact prevalence and the best method to assess clubbing in FILDs. We aimed to study the prevalence of clubbing in patients with FILDs, to relate clubbing to disease severity, and to evaluate agreement between different assessment methods. Methods: Consecutive outpatients with FILD of two tertiary referral centers were included. Clubbing was assessed with the phalangeal depth ratio, the digital index, the Schamroth sign test, and by the treating physicians. Results: We included 153 patients (100 men), mean age 65 (range 33-88), mean FVC 79% (25-145%), mean DLCOc 50% (16-104%). Prevalence of clubbing ranged from 7-41% in the total group and 5-52% in IPF, depending on assessment method (table 1). Clubbing did not correlate with FVC or DLCOc (p>0.2). Kappa values between clubbing assessment methods ranged from -0.3–0.2. Conclusion: Clubbing was present in 7-41% of our FILD cohort, and showed no correlation with disease severity. Although considered an important clinical feature, assessment methods for clubbing showed no to poor agreement.