Bronchoalveolar lavage (BAL) has been crucial in elucidating the immune effector cells involved in the inflammatory processes in idiopathic interstitial pneumonias 1. Despite its value as a research tool, the diagnostic usefulness of BAL in idiopathic interstitial pneumonias is limited. An increase in neutrophils and/or eosinophils and/or lymphocytes may be seen. The idiopathic interstitial pneumonia with the worst prognosis is idiopathic pulmonary fibrosis (IPF) showing a histological pattern of usual interstitial pneumonia (UIP) 2. In IPF, historical data suggests that certain changes in BAL cell differentials may have prognostic importance; in some studies, patients with increased percentages of neutrophils or eosinophils (or both) had a worse prognosis, whereas BAL lymphocytosis has been associated with a greater responsiveness to corticosteroid therapy 3–6.
The most detailed data in that context have been published by Watters et al. 4. In their cohort, pretreatment BAL lymphocytosis was associated with significant subsequent clinical improvement. They also reported on the histology of their patients, evaluating 11 separate histological features. They found that BAL lymphcytosis was associated with moderate-to-severe alveolar septal inflammation and with a relative lack of histological honeycombing. These data suggested that BAL fluid lymphocytosis identifies a subset of patients with IPF who are more “cellular” in biopsy and likely to improve in response to corticosteroid therapy.
Katzenstein and Myers 7 already emphasised the limitations of this study. Only 19 patients were available for follow-up at 1 yr. Of these, five of …