Diagnostic uncertainties in patients with bacteraemia: impact on antibiotic prescriptions and outcome.

Objectives: To establish a formal diagnosis in infectious disease is not an easy task. Our aim was to characterize diagnostic uncertainty (DU) in patients for whom blood cultures were positive (PBC) and to determine its impact on both the antibiotic therapy and the outcome.

Methods: This was a prospective multicentre study including PBC for 6 months. The laboratory gave the PBC result to the infectious disease (ID) specialists in real time (24/7). The latter analysed all data from electronic patient charts and gave therapeutic advice to the physicians in charge of the patient to either initiate an antibiotic therapy, or to modify or to pursue continuing antimicrobial treatment. A DU was defined as no diagnosis of ID after thorough reading of the patient's chart, or more than two diagnoses despite two medical opinions obtained before PBC. An unfavourable outcome was defined by the occurrence of death during hospitalization.

Results: One hundred and nighty-nine PBCs were communicated to ID specialists, including 93 DUs (47%). In multivariate analysis, DU was associated with hospitalization in medical wards: [adjusted odds ratio (AOR) (95% CI): 6.94 (3.41-14.28)], the advice to initiate an antibiotic treatment: [3.89 (1.56-9.70)] and piperacillin-tazobactam use [3.75 (1.56-9.00)]; ICU requirement at initiation of care was a protective factor [0.38 (0.17-0.84)]. An unfavourable outcome was observed in 22 cases, and in a second logistic regression showed that DU was associated with the latter [AOR (95% CI): 5.07 (1.60-16.12)].

Conclusion: DUs were frequent during infections proved by PBC, and were associated with admission in medical wards, broad-spectrum antibiotic use and a high rate of unfavourable outcomes.