# Urinary 4-pyridoxic acid as a non-invasive biomarker for evaluating osteoarthritis severity: findings from the ROAD study

## TL;DR

This study explores urinary 4-pyridoxic acid as a non-invasive biomarker for assessing the severity of knee osteoarthritis in Japanese adults.

## Contribution

The study identifies urinary 4PA as a potential severity biomarker for knee osteoarthritis, particularly in advanced stages.

## Key findings

- Urinary 4PA levels were significantly higher in participants with KL grade 4 knee osteoarthritis compared to lower grades.
- The association remained significant after adjusting for age, sex, BMI, and lifestyle factors.
- No significant differences in 4PA levels were observed across lumbar spondylosis KL grades.

## Abstract

The early detection of osteoarthritis (OA) requires reliable biomarkers; however, reports identifying such biomarkers remain limited.

This study aimed to evaluate the potential of urinary 4-pyridoxic acid (4PA) as a biomarker for the severity of knee osteoarthritis (KOA) and lumbar spondylosis (LS) in Japanese adults, using data from the population-based cohort study.

Data were analysed from 1566 participants (510 men and 1,056 women) aged ≥ 40 years, who were enrolled in the Research on Osteoarthritis/Osteoporosis against Disability (ROAD) cohort, a population-based study initiated in 2005. Participants underwent radiographic assessments of the knees and lumbar spine, and urinary 4PA levels were measured using high-performance liquid chromatography. Logistic regression analyses were performed to evaluate the association between urinary 4PA levels and the Kellgren–Lawrence (KL) grade of KOA and LS, adjusting for age, sex, body mass index (BMI), and lifestyle factors.

Urinary 4PA levels were significantly higher in participants with KL grade 4 KOA compared to those with lower KL grades (p < 0.001). This association remained significant after adjusting for confounding factors. In contrast, no significant differences in 4PA levels were observed across the KL grades for LS, although a slight increase in 4PA levels was noted in KL grade 4 cases.

These findings suggest that urinary 4PA could serve as a biomarker for assessing KOA severity, particularly in advanced stages. While the detection of early OA using 4PA remains challenging, the significant increase in KL grade 4 cases highlights its potential role in guiding treatment decisions, such as surgical intervention.