Fine crackles on chest auscultation in the early diagnosis of idiopathic pulmonary fibrosis: a prospective cohort study

INTRODUCTION: Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease (ILD) with a poor prognosis. Early diagnosis and treatment of IPF may increase lifespan and preserve quality of life. Chest CT is the best test to diagnose IPF, but it is expensive and impractical as a screening test. Fine crackles on chest auscultation may be the only best to screen for IPF. METHODS: We prospectively assessed the presence and type of crackles on chest auscultation in all patients referred to the ILD Clinic at the Kingston Health Sciences Center in Ontario, Canada. Clinicians with varying levels of experience recorded the presence of fine crackles, coarse crackles or both independently and unaware of the final diagnosis. We applied multinomial logistic regression to adjust for ILD severity and factors that could affect the identification of crackles. RESULTS: We evaluated 290 patients referred to the ILD Clinic. On initial presentation, 93% of patients with IPF and 73% of patients with non-IPF ILD had fine crackles on auscultation. In patients with IPF, fine crackles were more common than cough (86%), dyspnoea (80%), low diffusing capacity (87%), total lung capacity (57%) and forced vital capacity (50%). There was 90% observer agreement in identifying fine crackles at a subsequent visit. In multiple regression analysis, the identification of fine crackles was unaffected by lung function, symptoms, emphysema, chronic obstructive pulmonary disease, obesity or clinician experience (p>0.05). CONCLUSIONS: Fine crackles on chest auscultation are a sensitive and robust screening tool that can lead to early diagnosis and treatment of patients with IPF.