The single most useful clinical sign of severity of in a person without underlying lung disease Is

CURB65 Each risk factor scores one point, for a maximum score of 5: Confusion of new onset (defined as an AMTS of 8 or less) Blood Urea nitrogen greater than 7 mmol/l (19 mg/dL) Respiratory rate of 30 breaths per minute or greater Blood pressure less than 90 mmHg systolic or diastolic blood pressure 60 mmHg or less Age 65 or older Ref Davidson edition23rd pg 583