Induced sputum compared to bronchoalveolar lavage for evaluating patients with sarcoidosis and non-granulomatous interstitial lung disease

Abstract

Broncholveolar lavage (BAL), an important tool for evaluating interstitial lung diseases (ILDs), has limited utility due to its invasiveness and the difficulty of performing it in clinically contraindicated patients. We compared BAL with the induced sputum (IS) technique to analyse cells and T lymphocytes in patients with sarcoidosis (SA) and non-granulomatous ILD (NG-ILD). Pulmonary function tests and BAL were performed by conventional methods. IS induction was done 20 sec after inhalation of 3·5% saline with an ultrasonic nebulizer. Giemsa-stained cytopreps were differentially counted. T lymphocyte subsets were analysed by flow activated cell sorter (FACS). Patients with NG-ILD had impaired total lung capacity (TLC). Transbronchial biopsy demonstrated lung fibrosis in NG-ILD and non-caseating granuloma in SA. The differential cell count in both groups demonstrated a significantly lower percentage of neutrophils and a significantly higher percentage of macrophages in BAL than in IS. The IS samples of patients with SA were significantly richer in metachromatic cells and eosinophils, but had a lower percentage of lymphocytes, compared to the BAL samples. The profiles of T cell subsets showed the same pattern, in both samples, in both groups. A CD4 CD8 ratio of 2·5 or greater had a sensitivity of 100% and a specificity of 81·2%, with a positive predictive value of 81·2% to distinguish SA from NG-ILD. IS is an effective non-invasive technique to identify CD4+ inflammation which distinguishes sarcoidosis from other NG-ILDs.