Material in this section is reproduced from Gulliford et al.31 This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 3.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/licenses/by/3.0/.
Data were analysed for 610 CPRD general practices, with 45,465,200 registered person-years of observation over the period from 2005 to 2014. The RTI consultation rate continued a long-term decline7 during the period from 2005 to 2014, reducing it from 256 to 220 per 1000 patient-years in men and from 351 to 307 per 1000 patient-years in women. The antibiotic-prescribing rate for RTI declined from 128 to 106 per 1000 patient-years in men and from 184 to 155 per 1000 patient-years in women. The proportion of RTI consultations with antibiotics prescribed declined from 53.9% to 50.5% in men, and from 54.5% to 51.5% in women.
General practices were divided into quartiles on the basis of the proportion of RTI consultations with antibiotics prescribed (Table 18). General practices in the highest quartile prescribed antibiotics at a median of 65% (range 58–79%) of RTI consultations, whereas general practices in the lowest quartile prescribed antibiotics at a median of 38% (range 29–44%) of RTI consultations. Age-standardised incidence rates for each of the infective complications are shown in Table 18. The incidence of pneumonia was 157 (95% CI 154 to 159) per 100,000 patient-years at low-prescribing practices, but 119 (95% CI 117 to 121) per 100,000 patient-years at high prescribing practices. The incidence of peritonsillar abscess was 15.6 (95% CI 15.5 to 15.8) per 100,000 patient-years at low-prescribing practices, but 12.9 (95% CI 12.8 to 13.0) per 100,000 patient-years at high prescribing practices. Mastoiditis, empyema and bacterial meningitis and intracranial abscess showed lower rates of incidence rates, which did not appear to be associated with antibiotic-prescribing category. There were 14 cases of Lemierre syndrome, evenly distributed between prescribing categories, with an overall incidence rate of 0.31 per one million patient-years.
| Variables | Quartiles of proportion of RTI consultations with antibiotics prescribed | |||
|---|---|---|---|---|
| High ≥ 58% | 51–58% | 44–51% | Low < 44% | |
| Number of general practices | 152 | 153 | 152 | 153 |
| Number of person-years from registered patients | 10,573,885 | 12,135,183 | 12,109,005 | 10,647,128 |
| Proportion of RTI consultations with antibiotics prescribed (median, 95% range) | 65 (58–79) | 54 (51–57) | 48 (45–51) | 38 (29–44) |
| Age- and gender-standardised incidence rate per 100,000 (95% CI) | ||||
| Pneumonia | 119.2 (117.0 to 121.3) | 129.1 (126.9 to 131.2) | 156.4 (154.0 to 158.7) | 156.6 (154.0 to 159.1) |
| Peritonsillar abscess | 12.9 (12.8 to 13.0) | 13.2 (13.1 to 13.3) | 14.1 (13.9 to 14.2) | 15.6 (15.5 to 15.8) |
| Mastoiditis | 3.48 (3.37 to 3.60) | 3.31 (3.21 to 3.42) | 3.32 (3.19 to 3.46) | 3.38 (3.25 to 3.51) |
| Empyema | 3.64 (3.27 to 4.01) | 4.00 (3.63 to 4.37) | 3.66 (3.31 to 4.01) | 4.00 (3.61 to 4.40) |
| Bacterial meningitis | 2.19 (1.90 to 2.47) | 2.16 (1.90 to 2.42) | 2.24 (1.97 to 2.51) | 2.45 (2.15 to 2.75) |
| Intracranial abscess | 0.37 (0.25 to 0.48) | 0.35 (0.24 to 0.46) | 0.55 (0.42 to 0.69) | 0.42 (0.29 to 0.55) |
| Lemierre syndrome | 4 cases | 3 cases | 2 cases | 5 cases |
A general practice with the mean list size for England of 7000 registered patients is expected to have 20,300 (95% range 11,340–30,380) consultations for RTIs over a period of 10 years (Table 19). A general practice of this size, with an average RTI consultation rate, may issue 13,195 (95% range 11,744–16,037) antibiotic prescriptions during this period if it is in the highest prescribing quartile. If the practice reduces the proportion of RTI consultations with antibiotics prescribed by 10%, the general practice will issue 20,300 (95% range 11,340–30,380) fewer antibiotic prescriptions for RTIs. This reduction in antibiotic prescribing is expected to be associated with 11 (95% range 6–15) more cases of pneumonia per decade, and 0.9 (95% range 0.5–1.3) more cases of peritonsillar abscess per decade (Table 19). Mastoiditis, empyema, bacterial meningitis, intracranial abscess and Lemierre syndrome are not expected to increase.
| Measure | Number expected in a general practice with 7000 patients over 10 years | Change over 10 years after a 10% absolute decrease in the proportion of RTI consultations with antibiotics prescribed |
|---|---|---|
| RTI consultations | 20,300 (11,340 to 30,380) | 0 |
| Antibiotic prescriptions for RTI | 13,195 (11,744 to 16,037)a | –2030 (–3038 to –1134)b |
| Number of first episodes | ||
| Pneumonia | 83 (82 to 85) | 11 (6 to 15) |
| Peritonsillar abscess | 9 (9 to 9) | 0.9 (0.5 to 1.3) |
| Mastoiditis | 2 (2 to 3) | 0 |
| Empyema | 3 (2 to 3) | 0 |
| Bacterial meningitis | 2 (1 to 2) | 0 |
| Intracranial abscess | < 1 | 0 |
Figure 14 shows the association between the antibiotic-prescribing rate and infective complications. Pneumonia showed an association with the antibiotic-prescribing rate [incidence rate ratio (IRR) 0.74, 95% range 0.58–0.95; p = 0.02], peritonsillar abscess showed a weak association (IRR 0.84, 95% range 0.68–1.03; p = 0.09), but the other bacterial infections did not.
FIGURE 14 Association of incidence of infective complications with quartile of antibiotic-prescribing rate. IRRs were adjusted for RTI consultation rate, gender, age group, region, deprivation quintile and clustering by general practice. AB rate, rate of antibiotic prescriptions for RTIs per 1000 registered patients; Ref., reference category. (Figure not reproduced here; see the original article.)
Table 20 shows IRRs estimated after fitting the predictors as continuous variables. These estimates are consistent with linear associations; adding quadratic terms did not improve the goodness of fit. Increasing the RTI consultation rate was associated with increasing incidence of pneumonia and mastoiditis. Increasing antibiotic-prescribing proportion was associated with a declining incidence of pneumonia and peritonsillar abscess. Each 10% increase in antibiotic-prescribing proportion was associated with a 12.8% (95% range 7.8–17.5%) relative decrease in pneumonia, and a 9.9% (95% range 5.6–14.0%) decrease in peritonsillar abscess. Associations with the antibiotic-prescribing rate fitted as a linear predictor were consistent with those for the antibiotic-prescribing proportion.
| Bacterial infection | RTI consultation rate (10 consultations per 1000 patient-years) | Antibiotic-prescribing rate for RTIs (10 antibiotic prescriptions for RTIs per 1000 patient-years) | Proportion of RTI consultations with antibiotics prescribed (for 10% increase) | |||
|---|---|---|---|---|---|---|
| RRa (95% CI) | p-value | RRb (95% CI) | p-value | RRb (95% CI) | p-value | |
| Pneumonia | 1.015 (1.008 to 1.023) | < 0.001 | 0.959 (0.941 to 0.976) | < 0.001 | 0.87 (0.83 to 0.92) | < 0.001 |
| Peritonsillar abscess | 1.004 (0.998 to 1.010) | 0.18 | 0.968 (0.953 to 0.982) | < 0.001 | 0.90 (0.86 to 0.94) | < 0.001 |
| Mastoiditis | 1.020 (1.005 to 1.034) | 0.007 | 1.008 (0.973 to 1.044) | 0.67 | 1.00 (0.90 to 1.12) | 0.95 |
| Empyema | 1.005 (0.995 to 1.016) | 0.35 | 0.979 (0.953 to 1.005) | 0.11 | 0.93 (0.86 to 1.01) | 0.10 |
| Bacterial meningitis | 1.001 (0.987 to 1.016) | 0.86 | 0.986 (0.949 to 1.023) | 0.45 | 0.94 (0.84 to 1.06) | 0.30 |
| Intracranial abscessc | 1.003 (0.984 to 1.022) | 0.75 | 0.986 (0.938 to 1.035) | 0.57 | 0.94 (0.81 to 1.09) | 0.40 |
A general practice with the mean list size for England of 7000 registered patients is expected to have 20,300 (95% range 11,340–30,380) consultations for RTIs over a period of 10 years (Table 20). A general practice of this size, with an average RTI consultation rate, may issue 13,195 (95% range 11,744–16,037) antibiotic prescriptions during this period if it is in the highest prescribing quartile. If the practice reduces the proportion of RTI consultations with antibiotics prescribed by 10% it will issue 2030 (95% range 11,340–30,380) fewer antibiotic prescriptions for RTIs. This reduction in antibiotic prescribing is expected to be associated with 11 (95% range 6–15) more cases of pneumonia per decade, and 0.9 (95% range 0.5–1.3) more cases of peritonsillar abscess per decade (Table 20). The number of cases of mastoiditis, empyema, bacterial meningitis, intracranial abscess and Lemierre syndrome is not expected to increase.