BACKGROUND: Proadrenomedullin (ProADM) confers additional prognostic information 
to established clinical risk scores in lower respiratory tract infections 
(LRTI). We aimed to derive a practical algorithm combining the CURB65 score with 
ProADM-levels in patients with community-acquired pneumonia (CAP) and 
non-CAP-LRTI.
METHODS: We used data of 1359 patients with LRTI enrolled in a multicenter 
study. We chose two ProADM cut-off values by assessing the association between 
ProADM levels and the risk of adverse events and mortality. A composite score 
(CURB65-A) was created combining CURB65 classes with ProADM cut-offs to further 
risk-stratify patients.
RESULTS: CURB65 and ProADM predicted both adverse events and mortality similarly 
well in CAP and non-CAP-LRTI. The combined CURB65-A risk score provided better 
prediction of death and adverse events than the CURB65 score in the entire 
cohort and in CAP and non-CAP-LRTI patients. Within each CURB65 class, higher 
ProADM-levels were associated with an increased risk of adverse events and 
mortality. Overall, risk of adverse events (3.9%) and mortality (0.65%) was low 
for patients with CURB65 score 0-1 and ProADM ≤0.75 nmol/l (CURB65-A risk class 
I); intermediate (8.6% and 2.6%, respectively) for patients with CURB65 score of 
2 and ProADM ≤1.5 nmol/l or CURB classes 0-1 and ProADM levels between 0.75-1.5 
nmol/L (CURB65-A risk class II), and high (21.6% and 9.8%, respectively) for all 
other patients (CURB65-A risk class III). If outpatient treatment was 
recommended for CURB65-A risk class I and short hospitalization for CURB65-A 
risk class II, 17.9% and 40.8% of 1217 hospitalized patients could have received 
ambulatory treatment or a short hospitalization, respectively.
CONCLUSIONS: The new CURB65-A risk score combining CURB65 risk classes with 
ProADM cut-off values accurately predicts adverse events and mortality in 
patients with CAP and non-CAP-LRTI. Additional prospective cohort or 
intervention studies need to validate this score and demonstrate its safety and 
efficacy for the management of patients with LRTI.
TRIAL REGISTRATION: Procalcitonin-guided antibiotic therapy and hospitalisation 
in patients with lower respiratory tract infections: the prohosp study; 
isrctn.org Identifier: ISRCTN: ISRCTN95122877.