Table 1.

Criteria for Diagnosis of Autoimmune Pulmonary Alveolar Proteinosis^*

Essential criterion

Abnormal serum GM-CSF autoantibody test result†

Supporting criteria

Chest HRCT scan showing diffuse ground-glass opacification and superimposed septal thickening (“crazy-paving sign”)‡

BAL cytopathology showing extensive, mostly extracellular, amorphous PAS-positive cell fragments/debris, ghost cells, and/or large foamy (PAS-positive, oil red O–positive) macrophages§

Lung biopsy histopathology showing alveoli filled with eosinophilic (PAS-positive) granular sediment, enlarged foamy-appearing alveolar macrophages, and/or cholesterol crystals (clefts)ǁ

Definition of abbreviations: GM-CSF = granulocyte/macrophage colony–stimulating factor; HRCT = high-resolution computed tomography; PAS = periodic acid–Schiff.

^*Diagnosis requires the presence of the essential criterion and any one of the supporting criteria.

^† Usually determined quantitatively by ELISA. The (laboratory-specific) cutoff value for an abnormal test result depends on the nature of the GM-CSF autoantibody reference standard and the assay protocol (see text for details).

^‡ Ground-glass opacification may occur without superimposed septal thickening in mild disease and usually but not always involves multiple lobes, with or without subpleural sparing.

^§ BAL fluid usually appears opalescent and milky white (or brown in smokers) and contains a waxy sediment, which appears quickly on standing at room temperature or in the cold.

^ǁ A lung biopsy is often unnecessary and should be performed only if clinically indicated (see text for details).