Fig. 1

Receiver operating characteristic curves for predicting 30-day mortality of non-elderly patients with community-acquired pneumonia. The risk score for non-elderly (range, 0–5) is calculated by summing the existence of the following characteristics: patient requires help with feeding; the existence of a malignancy (any malignancy including metastatic solid tumour); confusion; low blood pressure (systolic blood pressure ≤90 mmHg), and age 40–64 years. The A-DROP score (range, 0–5) is obtained by summing the existence of the following characteristics: confusion, dehydration (existence of a clinical sign of dehydration or blood urea nitrogen level ≥210 mg/L), respiratory failure (SpO₂ ≤ 90 % or PaO₂ ≤ 60 mmHg), a low blood pressure (systolic blood pressure ≤90 mmHg), and age. For A-DROP, scores for age are 0 points in all patients because all are <65 years. The area under the curve of the risk score for non-elderly (0.86, 95 % confidence interval [CI]: 0.84–0.87) is higher than that of the A-DROP score (0.72, 95 % CI: 0.70–0.74) (P < 0.0001)