Hemosiderin-laden Macrophages in the BAL Fluid of Patients with Diffuse Alveolar Damage

word count: 200) Quantification of hemosiderin-laden macrophages in the bronchoalveolar lavage fluid (BALF) has been used to diagnose diffuse alveolar hemorrhage (DAH) but has not been assessed in patients with diffuse alveolar damage (DAD). The current study analyzed BALF obtained in 21 patients with DAD diagnosed by surgical lung biopsy. The median age of 21 patients with DAD was 68 years (range, 18 to 79 years) and 14 (67%) were men; 12 patients (57%) were immunocompromised. The median percentage of hemosiderin-laden macrophages in the BALF was 5% (range, 0 to 90%), but was ≥20% in 7 patients (33%), fulfilling the commonly used BALF criterion for DAH. There was a trend toward a positive correlation between the percentage of hemosiderin-laden macrophages in the BALF and parenchymal hemorrhage assessed semiquantitatively on histopathologic analysis. Patients with ≥20% hemosiderin-laden macrophages in the BALF had a significantly increased mortality rate (p = 0.047) compared to those with <20%. In patients with an acute onset of diffuse lung infiltrates and respiratory distress, ≥20% hemosiderin-laden macrophages in the BALF can occur with DAD, and is not necessarily diagnostic of DAH. The finding of ≥20% hemosiderin-laden macrophages in the BALF is associated with a worse prognosis in patients with DAD.