Pneumonia severity at admission according to the CRB-65 score
| CRB-65 risk class | 2005, n (%) | 2006, n (%) | Total, n (%) |
| 1 (CRB-65 = 0) | 30 285 (16.22) | 33 982 (16.85) | 64 267 (16.55) |
| 2 (CRB-65 = 1, 2) | 127 652 (68.38) | 150 238 (74.48) | 277 890 (71.55) |
| 3 (CRB-65 = 3, 4) | 28 754 (15.40) | 17 495 (8.67) | 46 249 (11.91) |
| Total patients with valid data (n) | 186 691 | 201 715 | 388 406 |
The CRB-65 risk score is based on four parameters: C, mental confusion; R, respiratory rate ⩾30/min; B, systolic blood pressure <90 mm Hg or diastolic blood pressure ⩽60 mmHg; 65, age ⩾65 years.
One point is assigned in the case of the presence of each parameter, adding up to a minimum of zero and a maximum of four points. The CRB-65 risk score classification is then calculated as follows: CRB-65, 0 points equivalent to risk class 1; CRB-65, 1 or 2 points equivalent to risk class 2; CRB-65, 3 or 4 points or mechanical ventilation at admission equivalent to risk class 3.