Antibiotic Prescribing in Patients With COPD Exacerbations
The COPD cohort included 62,747 patients; half were aged ≥70 (52%) and half were male (Table 1). Half came from the two most deprived quintiles of the Index of Multiple Deprivation (51%), indicating relatively low socioeconomic status. The majority of patients were either current smokers (40%) or ex-smokers (49%) and half were overweight or obese (51%). High proportions of patients had been prescribed antibiotics (38%), anticholinergics (34%) or oral glucocorticoid therapies (17%) in the previous three months. Comorbidities were frequently recorded: 39% had a prior record of hypertension, 29% had a record of depression, 13% had a record of diabetes, and 8% had a record of heart failure. Just under half of patients were known to have severe (32%) or very severe COPD (13%).
Within the study population, 12,609 patients were identified as having had an exacerbation episode; these cases were matched by age and gender to up to three controls each, resulting in 35,299 controls. Exacerbations were inversely associated with affluence (most affluent quintile compared to median quintile, matched odds ratio (OR)=0.81 [95%CI 0.75–0.87]) and positively associated with being underweight (compared to healthy weight, OR=1.13 [95%CI 1.06–1.21]) and current or past smoking (compared to non-smoking, OR=1.42 [95%CI 1.30–1.55] and 1.38 [95%CI 1.27–1.50] respectively) (Table 2). Exacerbations were inversely associated with hypertension (OR 0.93 [95%CI 0.89–0.97]) and diabetes (OR 0.94 [95%CI 0.89–0.99]), and positively associated with depression (OR 1.17 [95%CI 12–1.22]). A higher proportion of cases had recently been prescribed oral glucocorticoid therapies (34%, OR 2.57 [95%CI 2.45–2.69]), anticholinergics (64%, OR 1.99 [1.91–2.08]) and antibiotics (51%, OR 1.95 [95%CI 1.87–2.03]) compared to the controls. In addition, 40% of cases were known to have severe or very severe COPD, compared to 27% of controls (very severe compared to mild COPD OR 2.12 [95%CI 1.95–2.32], severe compared to mild COPD OR 1.61 [95%CI 1.51–1.72]).
Table 3 shows the characteristics of exacerbation cases. A large number were prescribed an antibiotic (61%) or an oral corticosteroid (51%) on the date of the exacerbation record (70% of patients received either or both). The majority of exacerbations were managed in the primary care setting, as only 10% were referred to A&E, and only 7% were admitted to hospital for the COPD exacerbation, in the 7 days prior to and including the date of the exacerbation record.
The incidence rates of repeat exacerbation and all cause mortality were 13.0 and 6.1 per 10,000 person-years, respectively (Table 4). After adjustment for age and sex, the risk of outcomes was seen to be highest amongst patients with very severe COPD.
Whilst 61% of exacerbation cases were prescribed antibiotics, this proportion varied considerably between the 237 GP practices (interquartile range, 48–73%). In the 92 practices with at least 50 COPD patients, the proportion varied between 29% and 88% (interquartile range, 56–74%). Figure 1 shows a large proportion (25%) of GP practices with a prescribing rate outside that which might be expected, as indicated by their location outside of the confidence limits. GP practice explained 15% (95%CI, 12–19%) of the variability in antibiotic prescribing, after adjustment for patient characteristics (COPD hospitalisation, increased dyspnoea, age 80+, recent prescribing of oral glucocorticoid therapy or antibiotics, COPD severity, heart failure, underweight; all found to be inversely associated with antibiotic prescribing). The likelihood ratio test, comparing models with or without GP practice as a level, confirmed that clustering by GP practice was statistically significant (p<0.001).
(Enlarge Image)
Figure 1.
Variability of GP practice prescribing rates of antibiotics to COPD exacerbation cases with superimposed confidence limits (±3 standard errors) for all 237 practices with at least one case.
Results
Cohort 1: COPD Population
The COPD cohort included 62,747 patients; half were aged ≥70 (52%) and half were male (Table 1). Half came from the two most deprived quintiles of the Index of Multiple Deprivation (51%), indicating relatively low socioeconomic status. The majority of patients were either current smokers (40%) or ex-smokers (49%) and half were overweight or obese (51%). High proportions of patients had been prescribed antibiotics (38%), anticholinergics (34%) or oral glucocorticoid therapies (17%) in the previous three months. Comorbidities were frequently recorded: 39% had a prior record of hypertension, 29% had a record of depression, 13% had a record of diabetes, and 8% had a record of heart failure. Just under half of patients were known to have severe (32%) or very severe COPD (13%).
Cohort 2: Exacerbation Cases and Controls
Within the study population, 12,609 patients were identified as having had an exacerbation episode; these cases were matched by age and gender to up to three controls each, resulting in 35,299 controls. Exacerbations were inversely associated with affluence (most affluent quintile compared to median quintile, matched odds ratio (OR)=0.81 [95%CI 0.75–0.87]) and positively associated with being underweight (compared to healthy weight, OR=1.13 [95%CI 1.06–1.21]) and current or past smoking (compared to non-smoking, OR=1.42 [95%CI 1.30–1.55] and 1.38 [95%CI 1.27–1.50] respectively) (Table 2). Exacerbations were inversely associated with hypertension (OR 0.93 [95%CI 0.89–0.97]) and diabetes (OR 0.94 [95%CI 0.89–0.99]), and positively associated with depression (OR 1.17 [95%CI 12–1.22]). A higher proportion of cases had recently been prescribed oral glucocorticoid therapies (34%, OR 2.57 [95%CI 2.45–2.69]), anticholinergics (64%, OR 1.99 [1.91–2.08]) and antibiotics (51%, OR 1.95 [95%CI 1.87–2.03]) compared to the controls. In addition, 40% of cases were known to have severe or very severe COPD, compared to 27% of controls (very severe compared to mild COPD OR 2.12 [95%CI 1.95–2.32], severe compared to mild COPD OR 1.61 [95%CI 1.51–1.72]).
Cohort 2: Exacerbation Cases
Table 3 shows the characteristics of exacerbation cases. A large number were prescribed an antibiotic (61%) or an oral corticosteroid (51%) on the date of the exacerbation record (70% of patients received either or both). The majority of exacerbations were managed in the primary care setting, as only 10% were referred to A&E, and only 7% were admitted to hospital for the COPD exacerbation, in the 7 days prior to and including the date of the exacerbation record.
The incidence rates of repeat exacerbation and all cause mortality were 13.0 and 6.1 per 10,000 person-years, respectively (Table 4). After adjustment for age and sex, the risk of outcomes was seen to be highest amongst patients with very severe COPD.
Whilst 61% of exacerbation cases were prescribed antibiotics, this proportion varied considerably between the 237 GP practices (interquartile range, 48–73%). In the 92 practices with at least 50 COPD patients, the proportion varied between 29% and 88% (interquartile range, 56–74%). Figure 1 shows a large proportion (25%) of GP practices with a prescribing rate outside that which might be expected, as indicated by their location outside of the confidence limits. GP practice explained 15% (95%CI, 12–19%) of the variability in antibiotic prescribing, after adjustment for patient characteristics (COPD hospitalisation, increased dyspnoea, age 80+, recent prescribing of oral glucocorticoid therapy or antibiotics, COPD severity, heart failure, underweight; all found to be inversely associated with antibiotic prescribing). The likelihood ratio test, comparing models with or without GP practice as a level, confirmed that clustering by GP practice was statistically significant (p<0.001).
(Enlarge Image)
Figure 1.
Variability of GP practice prescribing rates of antibiotics to COPD exacerbation cases with superimposed confidence limits (±3 standard errors) for all 237 practices with at least one case.
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