Differential diagnosis | Investigation | Result |
Bacterial LRTI | BAL microscopy and culture | Negative |
Viral LRTI | BAL viral PCR and culture | Negative |
Fungal LRTI | BAL cytology and culture | Negative |
PCP | BAL cytology and PCR | Negative |
Pulmonary TB | BAL acid-fast bacilli stain and culture; Mantoux test | Negative |
Hypersensitivity pneumonitis | IgG and IgE precipitating antibodies to inhaled organic dusts | Negative |
Connective tissue disorder | Autoimmune screen | Negative |
Sarcoidosis | Serum ACE | Normal |
Alveolar haemorrhage syndrome# | ANCA, Anti-GBM and BAL-haemosiderin laden macrophages | Negative |
Histiocytosis | Bone marrow aspirate | Normal |
Immunodeficiency | Igs and HIV tests | Normal |
Congenital or acquired cardiac abnormality | Echocardiogram | Normal |
LRTI: lower respiratory tract infection; PCP: Pneuomocystis carinii pneumonia; TB: tuberculosis; BAL: bronchoalveolar lavage; Ig: immunoglobulin; ACE: angiotensin-converting enzyme; ANCA: anti-neutrophil cytoplasmic antigen; anti-GBM: anti-glomerular basement membrane antigen. #: Goodpasture’s disease or granulomatosis with polyangiitis (Wegener's).