Univariable association of diagnostic variables with bacterial lower respiratory tract infection (LRTI) and bacterial pneumonia in patients presenting with acute cough in primary care
| Diagnostic variable | No. (%) of all patients* n = 3104 | Patients with bacterial LRTI | Patients with bacterial pneumonia | No. (%) with missing data | ||
|---|---|---|---|---|---|---|
| No. (%) n = 539 | OR (95%CI)† | No. (%) n = 38 | OR (95%CI)‡ | |||
| History (day 1) | ||||||
| Age, mean ± SD | 50 ± 17 | 50 ± 16 | 1.00 (0.99–1.00) | 54 ± 17 | 1.01 (1.00–1.03) | 0 (0.0) |
| Age ≥ 75 yr | 230 (7) | 34 (6) | 0.81 (0.56–1.19) | 5 (13) | 1.91 (0.74–4.95) | 0 (0.0) |
| Sex, male | 1244 (40) | 221 (41) | 1.05 (0.87–1.27) | 16 (42) | 1.09 (0.57–2.08) | 0 (0.0) |
| Current smoker | 871 (28) | 162 (30) | 1.13 (0.92–1.38) | 11 (29) | 1.04 (0.52–2.11) | 3 (0.1) |
| Comorbidity§ | 856 (28) | 143 (27) | 0.94 (0.76–1.16) | 17 (45) | 2.14 (1.13–4.08) | 5 (0.2) |
| Illness duration before index consultation, d, mean ± SD | 10 ± 10 | 9.9 ± 8 | 1.00 (1.00–1.01) | 10.0 ± 7 | 1.00 (0.98–1.03) | 31 (1.0) |
| Discoloured sputum¶ | 1461 (50) | 307 (61) | 1.66 (1.36–2.02) | 24 (67) | 2.00 (0.99–4.01) | 197 (6.3) |
| Breathlessness | 1754 (57) | 326 (61) | 1.22 (1.01–1.48) | 23 (61) | 1.18 (0.61–2.27) | 4 (0.1) |
| Runny nose | 2212 (71) | 388 (72) | 1.05 (0.85–1.29) | 19 (50) | 0.40 (0.21–0.75) | 4 (0.1) |
| Fever | 1085 (35) | 216 (40) | 1.31 (1.08–1.58) | 29 (76) | 6.12 (2.89–12.97) | 5 (0.2) |
| Chest pain | 1433 (46) | 260 (48) | 1.11 (0.92–1.34) | 21 (55) | 1.44 (0.76–2.74) | 6 (0.2) |
| Myalgia | 1573 (51) | 283 (53) | 1.09 (0.91–1.32) | 23 (61) | 1.50 (0.78–2.88) | 4 (0.1) |
| Headache | 1742 (56) | 313 (58) | 1.10 (0.91–1.33) | 25 (66) | 1.51 (0.77–2.96) | 3 (0.1) |
| Diarrhea | 222 (7) | 39 (7) | 1.01 (0.71–1.45) | 3 (8) | 1.11 (0.34–3.65) | 4 (0.1) |
| Interference with daily activities | 1955 (63) | 355 (66) | 1.16 (0.95–1.41) | 26 (68) | 1.27 (0.64–2.53) | 3 (0.1) |
| Physical examination (day 1) | ||||||
| Crackles on lung auscultation | 289 (9) | 54 (10) | 1.11 (0.81–1.51) | 12 (33) | 5.01 (2.48–10.12) | 18 (0.6) |
| Heart rate ≥ 100/min | 117 (4) | 15 (3) | 0.69 (0.40–1.20) | 3 (8) | 2.19 (0.66–7.22) | 44 (1.4) |
| Respiratory rate ≥ 20/min | 659 (22) | 115 (22) | 1.01 (0.80–1.26) | 10 (27) | 1.34 (0.64–2.77) | 78 (2.5) |
| Blood pressure < 90/60 mm Hg | 79 (3) | 14 (3) | 1.03 (0.58–1.86) | 3 (8) | 3.40 (1.02–11.30) | 67 (2.2) |
| Temperature ≥ 38°C | 121 (4) | 25 (5) | 1.27 (0.81–1.99) | 4 (11) | 2.93 (1.02–8.41) | 31 (1.0) |
| Blood tests | ||||||
| CRP, mg/mL, mean ± SD | 19 ± 35 | 34 ± 53 | 1.01 (1.01–1.01) | 97 ± 98 | 1.02 (1.01–1.02) | 264 (8.5) |
| CRP > 20 mg/L | 648 (23) | 197 (39) | 2.67 (2.17–3.28) | 26 (68) | 7.59 (3.81–15.14) | 264 (8.5) |
| CRP > 30 mg/L | 456 (16) | 154 (31) | 2.95 (2.36–3.70) | 23 (61) | 8.39 (4.34–16.21) | 264 (8.5) |
| CRP > 100 mg/L | 100 (4) | 48 (10) | 4.61 (3.08–6.91) | 14 (37) | 18.42 (9.21–36.85) | 264 (8.5) |
Note: CI = confidence interval, CRP = C-reactive protein, OR = odds ratio, SD = standard deviation.
↵* Except where indicated otherwise.
↵† The OR compares patients with and without bacterial LRTI.
↵‡ The OR compares patients with and without bacterial pneumonia.
↵§ The following comorbidities were considered: pulmonary comorbidities (history of chronic obstructive pulmonary disease, asthma or other lung disease), cardiac comorbidities (history of heart failure, ischemic heart disease or other heart disease) and diabetes mellitus.
↵¶ Green, yellow or blood-stained.