[Diagnoses and diagnostic procedures in 500 consecutive patients with clinical suspicion of interstitial lung disease].

OBJECTIVE To determine the diagnostic yield achieved with the application of current recommendations for evaluating patients with suspected interstitial lung disease (ILD) and the procedures that must be applied to reach a definitive diagnosis. PATIENTS AND METHODS Over a 10-year period, 500 consecutive patients attending an ILD outpatient clinic who showed features of diffuse lung involvement were assessed with a single diagnostic protocol. Results were introduced in a dedicated database and diagnoses for idiopathic interstitial pneumonia were established according to a recent consensus classification. RESULTS A definitive diagnosis was reached in 427 (85%) patients: in 125 without invasive procedures and in 302 with invasive procedures. In 73 (14.6%) cases a definitive diagnosis was not reached, and patients were placed in the group of unclassifiable interstitial pneumonia. Idiopathic interstitial pneumonia was the predominant group with 193 (39%) patients. The main specific entities included sarcoidosis with 93 (19%) patients, usual interstitial pneumonia with 84 (17%) patients, and hypersensitivity pneumonitis with 75 (15%) patients. Thirty (6%) patients were diagnosed with an illness other than ILD (false ILD). In 332 patients, we performed a total of 433 invasive procedures: transbronchial biopsy in 252 (direct diagnostic yield, 38%, or if used also to exclude other specific diagnosis, 50%), bronchoalveolar lavage in 260 (yield, 5%), and open lung biopsy in 141 (yield, 93%). Hence, following the current diagnostic approach, a definitive diagnosis was established for 85% of patients, for 25% solely on clinical grounds and imaging criteria and for 60% on the basis of invasive procedures. Diagnosis by open lung biopsy was still required for 141 (28%) patients. CONCLUSIONS The diagnostic yield was high when the recommended study protocol was followed. A quarter of the diagnoses were reached with clinical criteria alone, but another quarter could only be made after open lung biopsy.