# Peripheral Blood Cells and Clinical Profiles as Biomarkers for Pain Detection in Palliative Care Patients

## TL;DR

This study explores blood cell markers and clinical factors to detect pain in palliative care patients, especially those who cannot self-report pain.

## Contribution

The study identifies novel peripheral blood biomarkers and clinical parameters for pain detection in palliative care patients.

## Key findings

- Chronic pain is linked to advanced age, reduced glomerular filtration rate, and malnutrition.
- Lymphocyte percentage and monocyte/platelet biomarkers like CD206, CD163, and CD59 show potential as pain predictors.
- A classification model suggests all patients over 65 in the sample reported pain.

## Abstract

Background/Objectives: Patients in need of specialized palliative care are clinically highly complex, with pain being the most prevalent problem. Furthermore, in these patients, a self-report for characterization of pain could be difficult to obtain. This cross-sectional, exploratory study investigates the use of clinical parameters and peripheral blood biomarkers for potentially identifying and characterizing pain (assessed using Pain Assessment in Advanced Dementia (PAINAD) and Numeric Scale (NS)) in patients under palliative care, including a population with dementia where pain is often underdiagnosed. Methods: Fifty-three patients with non-oncological diseases were analyzed in a cross-sectional study using medical and nursing records. Among previous biomarkers related to monocytes and platelets assessed by flow cytometry, we selected the most significative ones for pain characterization in a logistic regression analysis (multivariate analysis), alongside patient-specific characteristics such as renal function, nutritional status, and age. Results: Our exploratory findings suggest strong relationships between chronic pain and advanced age, reduced glomerular filtration rate (GFR), and malnutrition within this cohort. Furthermore, the percentage of lymphocytes, total and classical monocytes, the relative expression in monocytes of CD206, CD163, the CD163/CD206 ratio, and the relative expression in platelets of CD59 emerged as potential predictors of pain. Statistical analyses highlighted the challenges of multicollinearity among variables such as age, GFR, and nutritional status. A classification model further suggested that all patients over 65 years in our specific sample reported pain. Conclusions: This pilot study provides preliminary support for prior evidence linking chronic pain to aging, nutritional deficits, and renal impairment, and highlights potential novel peripheral blood biomarkers for pain assessment. This work emphasizes the promise of clinical and molecular biomarkers to improve pain detection and management, contributing to personalized and effective palliative care strategies.