Hemosiderin-laden macrophages in bronchoalveolar lavage fluid

Diffuse pulmonary hemorrhage syndromes occasionally present diagnostic problems if the clinical picture is not very typical. The presence of hemosiderin-laden alveolar macrophages in bronchoalveolar lavage (BAL) fluid is a useful diagnostic criterion for this entity. However, in many diffuse interstitial pulmonary diseases (DIPD) there is a lesion at the alveolocapillary barrier, and an exit of red blood cells could occur from the blood vessels, leading to the appearance of siderophages. The aim of this work was dual: to evaluate the presence and number of siderophages in different types of interstitial pulmonary disease and to compare the diagnostic yield of two ways of quantifying hemosiderin-laden macrophages. Three groups of patients--controls (n = 5), DIPD (n = 32) and diffuse pulmonary hemorrhage (n = 3)--were subjected to BAL, and a differential count was made on cytocentrifuged Diff-Quik- and Perl-stained preparations. On the latter, two different measurements were made: the number of macrophages laden with hemosiderin and a quantitative "score." The results of a conventional count (percent of Perl-positive macrophages) showed significant differences between the three groups considered overall. Applying a cutoff value of 20%, the sensitivity of this method was 100% and the specificity, 91.6%. The results of the hemosiderin score showed significant differences between the three groups. Applying a value of 50 as a cutoff, the sensitivity and specificity of the method were 100%. In control patients and carriers of DIPD, the percentage of alveolar macrophages was higher than in healthy subjects. Quantification of the hemosiderin content of alveolar macrophages improved the specificity of the diagnosis of diffuse pulmonary hemorrhage by BAL.