Table 1.
Association between diagnostic variables and pneumonia in 2820 patients presenting with acute cough in primary care. Figures are numbers (percentages) unless mentioned otherwise
| Diagnostic variable | Missing | Total (n=2820) | Pneumonia present (n=140, 5%) | OR (95% CI) | P value | |
|---|---|---|---|---|---|---|
| Univariable | Multivariable* | |||||
| History (day 1) | ||||||
| Mean (SD) age (years) | 0 (0.0) | 50 (17) | 54 (15) | 1.1 (1.0 to 1.2)† | 1.1 (0.9 to 1.2)† | 0.118 |
| Men | 0 (0.0) | 1128 (40) | 62 (44) | 1.2 (0.9 to 1.7) | NA | — |
| Current smoker | 2 (0.1) | 779 (28) | 64 (30) | 1.1 (0.8 to 1.5) | NA | — |
| Mean (SD) No of days’ illness before consultation | 30 (1.1) | 10 (10) | 9 (6) | 1.0 (0.9 to 1.0) | NA | — |
| Cough | 2 (0.1) | 2818 (100) | 140 (100) | 0.1 (0.0 to 0.8) | NA | — |
| Severe cough | 0 | 931 (33) | 56 (40) | 1.4 (1.0 to 2.0) | 1.1 (0.7 to 1.6) | 0.724 |
| Phlegm | 2 (0.1) | 2239 (79) | 120 (86) | 1.6 (1.0 to 2.6) | NA | — |
| Breathlessness | 1 (0.0) | 1594 (57) | 96 (69) | 1.7 (1.2 to 2.5) | 1.4 (1.0 to 2.1) | 0.025 |
| Severe breathlessness | 0 | 197 (7) | 17 (12) | 1.9 (1.1 to 3.4) | 1.3 (0.7 to 2.4) | 0.419 |
| Runny nose absent | 1 (0.0) | 808 (29) | 61 (44) | 2.0 (1.4 to 2.8) | 1.9 (1.3 to 2.7) | <0.001 |
| Fever | 3 (0.1) | 989 (35) | 82 (59) | 2.8 (2.0 to 3.9) | NA | — |
| Chest pain | 3 (0.1) | 1304 (46) | 80 (57) | 1.6 (1.1 to 2.2) | 1.2 (0.8 to 1.7) | 0.402 |
| Severe chest pain | 0 | 141 (5) | 13 (9) | 2.1 (1.2 to 4.0) | 1.5 (0.8 to 3.1) | 0.224 |
| Diarrhoea | 2 (0.1) | 199 (7) | 15 (11) | 1.6 (0.9 to 1.8) | 1.5 (0.8 to 1.8) | 0.165 |
| Interference with daily activities | 1 (0.0) | 1759 (62) | 96 (69) | 1.3 (0.9 to 1.9) | NA | — |
| Any comorbidity (pulmonary, cardiac, diabetes mellitus)‡ | 4 (0.1) | 768 (27) | 50 (36) | 1.5 (1.1 to 2.2) | 1.0 (0.7 to 1.5) | 0.960 |
| Physical examination (day 1) | ||||||
| General toxicity | 5 (0.2) | 739 (26) | 43 (31) | 1.3 (0.9 to 1.8) | 1.1 (0.7 to 1.6) | 0.728 |
| Diminished vesicular breathing | 15 (0.5) | 362 (13) | 31 (22) | 2.0 (1.3 to 3.1) | 1.7 (1.1 to 2.6) | 0.013 |
| Crackles | 13 (0.5) | 265 (9) | 45 (32) | 5.3 (3.6 to 7.7) | 3.5 (2.3 to 5.2) | <0.001 |
| Tachycardia (pulse >100 beats/min) | 36 (1.3) | 111 (4) | 17 (12) | 3.8 (2.2 to 6.6) | 2.3 (1.3 to 4.3) | 0.003 |
| Tachypnoea (>24 breaths/min) | 67 (2.4) | 55 (2) | 6 (4) | 2.4 (1.0 to 5.7) | 1.4 (0.9 to 2.0) | 0.421 |
| Blood pressure <90/60 mm Hg | 58 (2.1) | 71 (3) | 9 (6) | 2.9 (1.4 to 5.9) | NA | — |
| Temperature >37.8°C | 27 (1.0) | 158 (6) | 22 (16) | 3.5 (2.1 to 5.7) | 2.5 (1.4 to 4.4) | <0.001 |
| Blood test results (day 1) | ||||||
| CRP (mg/L): | ||||||
| Mean (SD) | 142 (5.0) | 19 (35) | 69 (83) | 1.2 (1.1 to 1.2)§ | 1.1 (1.1 to 1.2)§ | <0.001 |
| >20 | 142 (5.0) | 726 (26) | 85 (61) | 4.9 (3.5 to 7.0) | 3.5 (2.4 to 5.0) | <0.001 |
| >30 | 142 (5.0) | 501 (18) | 74 (53) | 5.9 (4.2 to 8.4) | 3.8 (2.7 to 5.5) | <0.001 |
| >50 | 142 (5.0) | 255 (9) | 58 (41) | 8.9 (6.2 to 12.9) | 4.8 (3.2 to 7.1) | <0.001 |
| >100 | 142 (5.0) | 96 (3) | 34 (24) | 13.5 (8.5 to 21.5) | 6.0 (3.6 to 10.0) | <0.001 |
| Procalcitonin (µg/L): | ||||||
| Mean (SD) | 156 (5.5) | 0.09 (0.6) | 0.37 (2.6) | 1.2 (1.1 to 1.3)¶ | 1.2 (1.1 to 1.3)¶ | <0.001 |
| >0.25 | 156 (5.5) | 107 (6) | 20 (14) | 2.8 (1.7 to 4.6) | 2.2 (1.3 to 3.8) | <0.001 |
| >0.50 | 156 (5.5) | 78 (3) | 14 (10) | 4.5 (2.5 to 8.3) | 3.2 (1.7 to 6.3) | <0.001 |
NA=not analysed.
*Variables entered in model, based on literature: age, breathlessness, runny nose, chest pain, diarrhoea, comorbidity (pulmonary, cardiac, or diabetes), general toxicity, diminished vesicular breathing, crackles, tachycardia, tachypnoea, temperature >37.8°C. Both backward and forward selection showed same results. ORs after internal validation are shown.
†Per 10 years.
‡Pulmonary comorbidity=history of asthma or COPD (chronic obstructive pulmonary disease). Cardiac comorbidity=history of heart failure or ischaemic heart disease.
§Per 10 mg/L increase.
¶Per 0.10 µg/L increase.