Table 2.
Crude counts and rates of outcome variables (testing for the presence of a Hawthorne effect)
| Variable | Category | CPRD-GM | CPRD-xGM | SLS COPD |
| n | 2049 | 16 758 | 1403 | |
| Count of AECOPD episodes* | Number of events | 2693 | 20 184 | 2288 |
| Rate per person-year (95% CI) | 1.63 (1.57 to 1.69) | 1.53 (1.51 to 1.56) | 1.91 (1.83 to 1.99) | |
| Count of strict definition of AECOPD†episodes | Number of events | 583 | 3497 | 766 |
| Rate per person-year (95% CI) | 0.32 (0.30 to 0.35) | 0.24 (0.24 to 0.25) | 0.58 (0.54 to 0.62) | |
| Mortality | Number of cases | 144 | 1145 | 24 |
| Rate per 1 000 person-years (95% CI) | 78.19 (65.94 to 92.06) | 78.49 (74.01 to 83.17) | 17.51 (11.22 to 26.05) | |
| Number of days contact with primary care | Count | 48 167 | 399 291 | 66 308 |
| Rate per person-year (95% CI) | 26.19 (25.96 to 26.43) | 27.37 (27.29 to 27.46) | 49.11 (48.74 to 49.49) | |
| Countof COPD-related prescription items‡ | Count | 25 433 | 187 396 | 32 133 |
| Rate per person-year (95% CI) | 13.81 (13.64 to 13.98) | 12.85 (12.79 to 12.90) | 23.44 (23.18 to 23.70) | |
| Treatment switching§ | % switch at some point in follow-up | 36.16 | 40.77 | 34.67 |
For full definitions of above outcomes, see online supplementary appendix 1.
*AECOPD events were those that met any criteria from the validated algorithm.16
†The strict definition of AECOPD events was strictly medical codes for acute exacerbation of COPD.
‡Prescription of any treatment counted as usual care in SLS COPD.
§Switching from one treatment class to another during follow-up.
AECOPD, acute exacerbations of COPD; COPD, chronic obstructive pulmonary disease; CPRD-GM, Clinical Practice Research Datalink in Greater Manchester; CPRD-xGM, Clinical Practice Research Datalink outside of Greater Manchester; SLS COPD, Salford Lung Study in chronic obstructive pulmonary disease.