Table 1. Characteristics of included studies.
| Study | Study Center | Sample Size | Age | Diagnosis Method | Diagnosis Method | Result | Result | NOS |
|---|---|---|---|---|---|---|---|---|
| Asthma | COPD | COPD only | ACOS | |||||
| Shirtcliffe et all (2010) [10] | New Zealand | 749 | 25–75 | 1. Reversibility test (+ve if ≥ 12%/200ml change in FEV1), Or 2. Peak Expiratory Flow (PEF) variability (+ve if ≥ 20% change in FEV1), Or 3. Physician Diagnosed Asthma +Current symptoms, Or 4. Physician Diagnosed Asthma + inhaler use in the preceding 12 months | Post bronchodilator spirometry (FEV1/FVC <0·70) | 51 | 65 | 7 |
| Menezes et al (2013) [11] | Brazil, Chile, Mexico, Uruguay, Venezuela (PLATINO) | 5,044 | ≥40 | 1. Wheezing in the last 12 months + post-BD increase in FEV1 or FVC of 200 ml and 12%, Or 2. Self-reported prior diagnosis of asthma. | 1. Post bronchodilator spirometry (FEV1/FVC <0·70), OR 2. Lower limit of normality (defined as the lower 5th percentile for predicted post-BD FEV1/FEV and FEV1/FVC). | 594 | 89 | 6 |
| Marsh et al (2008)[12] | New Zealand | 469 | 65.4 (6.3) | 1. FEV1 bronchodilator reversibility ≥15%, Or 2. Had peak flow variability ≥20%, Or 3. Had a physician’s diagnosis of asthma and (current symptoms and/or inhaler use). | Post bronchodilator spirometry (FEV1/FVC <0·70) | 43 | 53 | 5 |
| Kauppi et al (2011) [13] | Finland | 1,546 | 56(12) | Based on the British Guidelines on Asthma Management with one or more of the following findings: a post bronchodilator increase in FEV1 of ≥12%, a bronchodilator response of ≥15% or diurnal variation of ≥20% in PEF recording, moderate to severe bronchial hyper-reactivity, or a decrease in FEV1 of ≥15% in the exercise test. | Post bronchodilator spirometry (FEV1/FVC < 0.70 OR FEV1/FVC < 88% of predicted reference value) | 237 | 225 | 7 |
| Hardin et al (2011)[14] | USA | 915 | 45–80 | Self Reported Physician Diagnosis of Asthma prior to the age of 40 | Post bronchodilator spirometry (FEV1/FVC < 0.7 and FEV1 < 80% predicted) | 796 | 119 | 5 |
| Alonso et al (2013) [15] | Spain | 331 | > = 40 | Physician Diagnosed Asthma before age 40 | Post bronchodilator spirometry (FEV1/FVC <0·70) | 291 | 40 | 5 |
| Johannessen et al (2005) [16] | Norway | 908 | 41 (15) | Self Reported Physician Diagnosis of Asthma | Post bronchodilator spirometry (FEV1/FVC <0·70) | 30 | 10 | 6 |
| Danielsson et al (2010) [17] | Sweden | 548 | ≥40 | Physician Diagnosed Asthma | Post bronchodilator spirometry (FEV1/FVC <0·70) | 70 | 16 | 7 |
| Methvin et al (2008) [18] | USA | 508 | ≥40 | Self Reported Physician Diagnosis of Asthma | Post bronchodilator spirometry (FEV1/FVC <0·70) | 72 | 28 | 5 |
| Miravitlles et al (2013) [19] | Spain | 3,885 | 40–80 | Self Reported Physician Diagnosis of Asthma | Post bronchodilator spirometry (FEV1/FVC <0·70) | 318 | 67 | 5 |
| Zhou et al (2009)[20] | China (CESCOPD) | 20,245 | ≥40 | Physician Diagnosed Asthma | Post bronchodilator spirometry (FEV1/FVC <0·70) | 1477 | 191 | 5 |
| Kotaniem et al (2005) [21] | Finland | 683 | 21–70 | Based on the following criteria: (self-reported asthma or had a positive skin-prick test) and (had reported attacks of respiratory obstruction or wheezing). | Post bronchodilator spirometry (FEV1/FVC <0·70) | 52 | 12 | 6 |
| Fabrri et al (2002) [22] | Italy | 46 | ≥ 30 | Physician Diagnosed Asthma | Post bronchodilator spirometry (FEV1/FVC <0·70) | 27 | 19 | 6 |
| Rhee et al (2013)[23] | Korea | 185,147 | > 40 | 1. ICD-10 codes for asthma (J45.x- J46), 2. Use of more than one drug for asthma at least twice per year (LAMA, LABA, ICS, ICS+LABA, SAMA, SABA, theophylline, LTRA, systemic corticosteroids, or systemic beta agonist). | 1. Age greater than 40 years, 2) ICD-10 codes for COPD or emphysema (J42.x–J44.x, except J430), 3. Use of more than one drug for COPD at least twice per year (LAMA, LABA, ICS, LABA+ICS, SAMA, SABA, or Theophylline). | 84143 | 101004 | 6 |
| Blanchette et al (2008)[24] | USA | 8,086 | ≥ 40 | 1. Age greater than 40 years, and 2. Have at least 1 medical claim with an ICD-9-CM code for COPD and at least 1 medical claim for asthma (493.0x, 493.1x, 493.8x, 493.9x) during the identification period and 3. Either (at least 1 additional claim with an ICD-9-CM code for COPD and asthma (493.2x) OR at least 1 additional medical claim for COPD and at least 1 additional claim for asthma within the observation period). | 1.age greater than 40 years, AND 2. ICD-9 codes for COPD (491.xx for chronic bronchitis, 492.xx for emphysema, or 496.xx for chronic airway obstruction not classified elsewhere), AND 3. Have at least 1 additional medical claim with an ICD-9-CM code for COPD during the 24-month observation period. | 6243 | 1843 | 6 |
| De marco et al (2010) [25] | Italy | 8360 | 20–84 | The GEIRD Screening Questionnaire(Physician Diagnosed) | The GEIRD Screening Questionnaire (Physician Diagnosed) | 431 | 175 | 5 |
| Shaya et al (2008)[26] | USA | 9131 | ≥ 40 | 1. Age 40 to 64 years, AND 2. At least 1 claim with ICD-9 code for Asthma (493.xx) in the primary, secondary, or tertiary diagnosis field. | 1. Age 40 to 64 years, AND 2. At least 1 claim with ICD-9 codes for COPD (491.xx, 492.xx, 496.xx). | 3455 | 2604 | 6 |
Abbreviations and definitions: COPD = chronic obstructive pulmonary disease; FEV1 = forced expiratory volume in 1 second; FVC = forced vital capacity, ICD: International Classification of Diseases.