(309) Relative Elevations of CRP and Procalcitonin and Association With Outcomes: A Multicentric Study

Introduction: C-Reactive Protein (CRP) and procalcitonin (Procal) are often measured in hospitalized patients to assess the severity of inflammation and guide therapy. While CRP and procalcitonin have been studied individually, there is limited information on their relative increases and association with outcomes. The objective of this study was to describe the CRP and procal phenotypes based on their elevation at the time of admission, and their association with mortality in heterogeneous cohort of patients of all ages.

Methods: Study included 15 hospitals of OSF HealthCare from 01/2019 to 12/2023. Patients admitted to the hospital from ED, who had both procal and CRP measured within 24 hours of admission, were included. CRP and procal levels were classified as normal or abnormal based on laboratory cutoffs (CRP > 0.5 mg/dl, and procal > 0.25 ng/ml). Patients were then classified into four phenotypes: group A, both normal; group B, both abnormal; group C, CRP abnormal/procal normal; and group D, procal abnormal/CRP normal. Outcomes, including hospital length of stay and mortality, were compared across the four groups.

Results: 10,403 patients met the study criteria (911 pediatric, 7735 non-Hispanic White). The median initial procalcitonin value was 0.17 ng/ml (IQR 0.06 – 0.69), with 4,192 (42%) being abnormal, and the median CRP value was 5.19 mg/dl (IQR 1.33, 12.56), with 9,044 (87%) being abnormal. The relative distribution in the four groups was: group A, 1,150 (11%); group B, 3,987 (38.3%); group C, 5,057 (48.6%); and group D, 205 (1.9%). Overall mortality was 11.2% (1,167/10,403), with 3.8%, 16.8%, 8.8%, and 1.4% in groups A, B, C, and D respectively. Compared to group A, the odds of mortality in group B were 5.07 (95% CI 3.71, 6.93, p< 0.001), in group C were 2.44 (95% CI 1.78, 3.36, p< 0.001), and in group D were 0.37 (95% CI 0.11, 1.21, p=0.10). The overall median hospital length of stay was 4 days (IQR 2, 7). There was a significant difference in hospital length of stay among the four groups (2 days [IQR 1, 4] for group A, 5 days [IQR 3, 9] for group B, 4 days [IQR 2, 6] for group C, and 2 days [IQR 1, 4.5] for group D, p< 0.001).

Conclusions: CRP and procal are often discrepantly elevated in hospitalized patients, and their relative elevations may provide additional prognostic information.