Table 3.

Hypothetical examples of causes of increased mortality when the cause of acute respiratory failure is not identified

	Unidentified, unsuspected, and untreated condition	Unidentified, suspected, but suboptimally treated condition	Undocumented coinfection in which one pathogen remains untreated	Infectious and non-infectious condition, of which one is unidentified or untreated	Identified aetiology mistakenly considered as irrelevant finding
Actual underlying cause	Pneumonitis while taking checkpoint inhibitors	Lung infiltration by lymphoma	Tuberculosis in a kidney transplant recipient	Pneumocystis pneumonia in a patient with lung cancer	Invasive aspergillosis
Incorrectly presumed cause	Positive nasal swab (rhinovirus) in a patient treated for melanoma; no clinical sign of viral infection	Patient treated for bacterial infection based on high plasma C-reactive protein and procalcitonin	The only positive result is a positive PCR for cytomegalovirus (2 logs)	Patient receiving steroids for radiation pneumonitis without prophylaxis	Patient believed to have an undetermined acute respiratory failure cause
Procedure that should have been performed	CT scan suggested hypersensitivity pneumonia; bronchoalveolar lavage cell analysis was not performed	CT-guided lung biopsy (the diagnosis of lymphoma was made based on node and bone marrow biopsies)	CT findings suggested tuberculosis with 3 apical cavitated nodules in the right upper lobe	As hypoxaemia worsened and ground-glass opacities extended, bronchoalveolar lavage should have been considered	Galactomannan at 0·50 and sputum positive for Aspergillus fumigatus, both considered irrelevant
Missed treatment	Steroids; drug withdrawal	Chemotherapy	Antituberculosis drugs	Trimethoprim and sulfamethoxazole	Antifungal agents