Prognostic Value of the CALLY Index in Patients With Sepsis

Sepsis is a life-threatening condition characterized by a dysregulated host response to infection and is frequently associated with multiorgan dysfunction and high mortality. Early identification of patients at increased risk of poor outcomes remains a major challenge in critical care. The C-reactive protein-albumin-lymphocyte (CALLY) Index is a composite biomarker that reflects inflammatory, nutritional, and immune status. Although recent studies have explored the prognostic value of CALLY in critically ill populations, the significance of serial measurements and temporal changes in patients with sepsis has not been fully established.

This retrospective observational study will include adult patients diagnosed with sepsis according to Sepsis-3 criteria who were admitted to the intensive care unit (ICU) between January 2023 and December 2024. The CALLY Index will be calculated using the following formula:

Albumin (g/L) × lymphocyte count (10⁹/L) × 100 ÷ CRP (mg/L).

CALLY values will be obtained at predefined time points: Day 0 (within 2 hours of ICU admission), Day 3, and Day 5, extracted from the hospital's electronic medical record system.

The primary aim of the study is to evaluate the association between CALLY Index values and 30-day all-cause mortality. Secondary aims include assessing the relationship between temporal changes in CALLY (ΔCALLY₃-₀, ΔCALLY₅-₀, and linear trend slope) and the development of acute kidney injury (AKI) within the first 7 days of ICU admission, as well as examining correlations between the Day-0 CALLY Index and commonly used clinical severity scores, including SOFA and APACHE II.

All study data will be obtained retrospectively from the hospital's electronic records. No additional tests, procedures, or interventions will be performed. As the study utilizes existing clinical data without influencing patient management, it poses no additional risks to participants. The findings may support improved early risk stratification, monitoring of disease progression, and refinement of prognostic assessment in patients with sepsis.

Inclusion criteria

• Age ≥ 18 years

• Sepsis diagnosis meeting Sepsis-3 criteria
• ICU stay ≥ 5 days
• Complete CRP, albumin, and lymphocyte laboratory results available for days 0, 3, and 5

Exclusion criteria

• • Chronic Kidney Disease stage ≥3

• Liver diseases including cirrhosis, chronic hepatitis, or hepatic failure
• Hematologic diseases such as leukemia, lymphoma, MDS, or multiple myeloma
• Rheumatologic diseases including SLE, rheumatoid arthritis, or systemic sclerosis
• Use of immunosuppressive therapy
• ICU stay shorter than 5 days
• COVID-19 positive status
• Missing laboratory data preventing calculation of CALLY index