Table 1– Characteristics of studies included in the meta-analysis that aimed to calculate the case fatality of a chronic obstructive pulmonary disease (COPD) exacerbation

First author [ref.]	Patients n	Males %	Mean age yrs	Mean FEV₁% pred	Patient selection	Definition exacerbation	Mean hospital length of stay days	Country
Connors 15	1016	51	70	0.80 L, ∼30% pred	Patients (aged >18 yr) with clinical diagnosis of COPD recorded by a physician	Hospitalisation in combination with breathlessness, respiratory failure or change in mental status due to COPD as main reason for admission and P_a,CO₂ ≥50 mmHg	9	USA
Vestbo 16	487	55	67	60	Patients (aged >20 yr) admitted for COPD (Copenhagen City Heart Study)	Hospitalisation (>24 h) with primary diagnosis ICD-8: 491–492	Not reported	Denmark
Groenewegen 17	171	61	70	35	Patients with COPD (ATS criteria), with a FEV₁<70% and reversibility <11% who were admitted	Increase of two out of three symptoms: dyspnoea, cough, sputum severe enough to warrant hospitalisation	11.7	Netherlands
Gunen 18	205	88	65	38	Patients with COPD (ATS criteria) who were admitted	Hospitalisation for severe increase of symptoms (cough, purulent sputum and dyspnoea), cyanosis and oedema, confusion, lethargy, coma, use of accessory muscles for ventilation, treatment failure, acidosis, hypoxaemia and/or hypercapnia or new arrhythmias	11.6	Turkey
McGhan 19	54269	97	69	Not reported	Patients admitted for COPD	Hospitalisation with primary diagnosis ICD-9: 490–492 or 496 or diagnosis related group code of COPD with a primary or secondary discharge diagnosis of COPD	6.5	USA
Brekke 20	996	49	71	47	Patients (aged >40 yr) admitted for COPD	Hospitalisation with primary discharge diagnosis ICD-10: J44.0, J44.1, J44.x with J13-J18.9	Not reported	Norway

FEV₁: forced expiratory volume in 1 s; % pred: % predicted; ATS: American Thoracic Society; P_a,CO₂: arterial carbon dioxide tension; ICD: International Classification of Diseases.