TABLE 1

Study characteristics

Studies by incidence of exacerbationCountryCare settingCohort studyPatients#Mean age yearsMean FEV1 % predMales %Definition of exacerbationFollow-up yearsEvents in the analysisPerson-years of follow-upIncidence exacerbations per year per person
Low
 Bertens [29]NetherlandsOutpatient primary careProspective243/240737168Event-basedup to 2>70 (70 patients with ≥1 event)480>0.15
 Bertens [29] (validation)NetherlandsOutpatient primary careProspective793/793677153Event-basedup to 2>222 (222 patients with ≥1 event)1586>0.14
 Parshall [47]UKOutpatient primary careProspective309/127705056Symptom-basedup to 1>98 (98 patients with ≥1 event)127>0.77
 Motegi [43]JapanOutpatient secondary careProspective232/183715693Symptom- and event-basedup to 21933660.53
 Almagro [23]SpainOutpatient secondary careProspective679/606734590Event-basedup to 0.25 and 1>98 (98 exacerbators to 3 months of follow-up period; data from [51])139.3>0.70
 Almagro [23] (validation)SpainOutpatient secondary careProspective395/377724194Event-based1
 Jones [38]EnglandOutpatient secondary careProspective297+/175§674271Symptom-basedup to 95015750.03
 Suetomo [48]JapanOutpatient secondary or tertiary careProspectiveNot reported/123676487Symptom-basedƒup to 1106##1230.87
 Müllerova [45]12 countriesSecondary and tertiary careProspective2164/2138634865Event-basedup to 314525725¶¶0.25
 Thomsen [50]DenmarkOutpatient tertiary careProspective++8020/6574678047Event-based4 (median)3083262960.12
 Moberg [42]DenmarkOutpatient tertiary careProspective695/674693736Unclear5.5 (mean)>421 (421 patients with ≥1 event)3822§§>0.11
 Ong [46]SingaporeOutpatient tertiary careRetrospective127/127714491Symptom-based1.35 (mean)318 (calculated using mean number of admissions (2.5))171ƒƒ0.08
 Takahashi [49]JapanOutpatient tertiary careProspective109/937355100Symptom-basedup to 192###930.88
 Faganello [33]BrazilOutpatient tertiary careProspective120/120656171Event-basedup to 1>95 (32 (27%) patients with 1 episode, 21 (18%) with 2 episodes, 7 (6%) with ≥3 episodes of exacerbation)120>0.79
 Garcia-Aymerich [34]SpainOut- and inpatient tertiary careProspective346/312693692Symptom-based1.1 (mean)>197 (63% of the patients (197) with ≥1 event)343>0.57
 Ko [39]ChinaInpatient tertiary careProspective327/243745286Event-basedup to 3>186 (186 patients with ≥1 readmission for AECOPD)7290.26
 Brusse-Keizer [30]NetherlandsInpatient tertiary careControl arm of RCT121/121655884Event-basedup to 1>62 (31 patients with ≥2 events)121>0.51
 Echave [32]SpainInpatient tertiary careProspective120/93714389Event-basedup to 1>61 (61 patients with ≥1 event)93>0.65
 Gudmundsson [35]Sweden, Norway, Finland, Iceland, DenmarkInpatient tertiary careProspective416/406693449Event-basedup to 1>246 (246 patients with ≥1 readmission;)406>0.61
 Amalakuhan [28]USARetrospectiveNot reported/106Unclear (presumably event-based)up to 1>100 (50 patients with ≥2 events)106>0.94
Moderate
 Lee [40]China, Taiwan, Korea, AustraliaOutpatient secondary or tertiary careProspective545/495694788Symptom-basedup to 0.5>338 (338 patients with ≥1 event; 226 had instead ≥1 moderate-to-severe exacerbation)247.5>1.37
 Moy [44]USAOutpatient secondary or tertiary careProspective173/167715499Event-based¶¶¶1.25 (mean)263¶¶¶2101.25
 Marin [41]SpainOutpatient tertiary careProspective275/2756549100Event-based5.1 (median)2735 (incidence multiplied by person-years)1402+++1.95
 Hurst [36]12 countriesInpatient tertiary careProspective2164/2138634865Event-basedup to 36927 (incidence multiplied by person-years)5725§§§1.21
High
 Chen [31]TaiwanOutpatient secondary careProspective150/143724973Event-based14 daysƒƒƒ315.55.65
 Jacob [37]CanadaOutpatient secondary or tertiary careProspective115/115674347Event-based1.5 (mean)683 (incidence multiplied by person-years)2073.30
 Almagro [27]SpainInpatient tertiary careProspective156/129723693Event-based1335 (incidence multiplied by person-years)1292.60

  • Where data are not displayed, they were not reported and/or not straightforward to evaluate. The incidence of exacerbations category is indicated as low, moderate or high when the exacerbation rate is <1 exacerbation per person-year, between 1 and 2 exacerbations per person-year or >2 exacerbations per person-year, respectively. Age and forced expiratory volume in 1 s (FEV1) % pred refer to the mean in the study population. RCT: randomised controlled trial; AECOPD: acute exacerbations of chronic obstructive pulmonary disease. #: number of patients in cohort/number of patients in analysis; : slightly different data are provided for the other outcome analysed in the paper (healthcare use); +: data from [52]; §: for which dyspnoea, obstruction, smoking and exacerbation index scores were available; ƒ: the outcome hospital readmission for exacerbation was also analysed in the paper; ##: obtained from the data event per patients in each of the two categories (high chronic obstructive pulmonary disease (COPD) assessment test group and low COPD assessment test group); ¶¶: proxy considering the patients included in the analysis (2138) and those completing the 3 years of follow-up (1679); ++: from a population-based cohort a subgroup of individuals with COPD was randomly selected; §§: obtained multiplying the number of patients in the study by the mean follow-up; ƒƒ: calculated using the mean follow-up value; ###: proxy obtained using the mean exacerbation frequency per year in the two categories (normal IgG-titer and high IgG-titer); ¶¶¶: two different outcomes analysed (number of acute exacerbations and COPD-related hospitalisation), only the data for the outcome acute exacerbations are presented; +++: proxy obtained from the median value for the follow-up; §§§: proxy considering the patients included in the analysis (2138) and the ones completing the 3 years of follow-up (1679); ƒƒƒ: a follow-up of 3 months was also analysed in the paper.