Association between admission biomarkers and clinical outcome in older adults diagnosed with an infection in the emergency department.

Introduction: In older adults, prognostic performances of admission biomarkers have been poorly investigated. This study aims to compare the prognostic abilities of usual admission biomarkers, especially PCT and CRP, for major clinical outcomes, comparing older to younger adults diagnosed with an infection in the ED, and to investigate the prognostic abilities of PCT and CRP depending on the glomerular filtration rate (GFR).

Methods: It was an observational, single-center, retrospective study, conducted in the Reims University Hospital, France. Endpoints were bacteremia, septic shock, and in-hospital mortality, related to the same ED visit.

Results: Over 1 year, 852 patients were included with 291 (34.2%) ≥75 years, and 127 (15.3%) patients had a GFR <30 mL.min^-1.1.73 m². Overall, 74 bacteremia, 56 septic shock and 82 in-hospital deaths have been observed. Prognostic abilities of admission biomarkers tended to be systematically lower in older compared to younger adults (PCT and CRP AUROC for bacteremia were, respectively, 0.71 and 0.62 in older adults vs 0.75 and 0.70 in younger adults; PCT and CRP AUROC for septic shock were, respectively, 0.71 and 0.66 in older adults vs 0.82 and 0.68 in younger adults). PCT showed a significant discriminating power for septic shock and in-hospital mortality only for GFR ≥ 30, and CRP showed a significant discriminating power for bacteremia and septic shock only for GFR ≥60.

Conclusion: Caution must be taken when interpreting admission biomarkers, as their prognostic abilities are lower in older adults or in patients with renal insufficiency diagnosed with an infection.