Table 5. Prospective observational studies of chronic dyspnoea diagnostic algorithms.

Study	Study population	Sample size	Algorithm details	Diagnostic yield
Pratter 2011 (13)	Patients referred to a specialist respiratory practice	123	Tier 1: history, examination, blood tests (FBC, TFTs, BNP, biochemistry), RFTs, CXR. Tier 2: CPET. Tier 3: respiratory: CT chest, V/Q scan, bronchoscopy, thoracocentesis; cardiac: stress echocardiogram, MPS, cardiac catheterisation; other: upper gastrointestinal endoscopy, CT sinuses	Tier 1: 37%. Tier 2: 31%. Tier 1+2: 68%. Tier 3: 32%. Overall: 99%
Pedersen 2007 (15)	Elderly patients presenting to primary care between 60 and 79 years of age	129	Step 1: ECG, spirometry. Step 2: echocardiogram, DLCO, Hb, TFTs. Step 3: cardiac MRI, cardiac stress testing, CXR	Step 1: 39%. Step 2: 24%. Steps 1+2: 63%. Step 3: 11%. Overall: 74%
Nielson 2001 (10)	Patients referred to hospital from primary care	284	Physical examination, ECG, CXR, spirometry, echocardiogram, FBC, TFTs, biochemistry.	Overall: 85%
DePaso 1991 (12)	Patients referred to a specialist physician with no diagnosis after history and examination and normal chest X-ray and spirometry	72	Step 1: repeat history and physical examination. Step 2: diagnostic step 1: confirmatory investigations undertaken; non-diagnostic step 1: TFTs, ABG, RFTs, V/Q scan, 2D echocardiogram, CPET, Holter monitor, bronchoprovocation testing, CT chest and upper GI series, 24 hour oesophageal pH monitoring	Step 1: 7%. Overall: 81%

CPET, cardiopulmonary exercise testing; ECG, electrocardiogram; FBC, full blood count; BNP, B-type natriuretic peptide; RFTs, respiratory function tests; CXR, chest X-ray; CT, computed tomography; MRI, magnetic resonance imaging; V/Q, ventilation/perfusion scan; DLCO, diffusing capacity of the lung for carbon monoxide; Hb, haemoglobin, TFTs, thyroid function tests.