# tRF‐30‐FP18LPMBQ4NK in Systemic Juvenile Idiopathic Arthritis: A Promising Diagnostic and Disease Activity Biomarker

## TL;DR

This study identifies a specific tRNA fragment that could help diagnose systemic juvenile idiopathic arthritis and assess disease activity.

## Contribution

The study introduces tRF-30-FP18LPMBQ4NK as a novel diagnostic and disease activity biomarker for sJIA.

## Key findings

- 245 tRFs were found to be differentially expressed in sJIA patients compared to healthy controls.
- tRF-30-FP18LPMBQ4NK levels were significantly higher in sJIA patients than in healthy controls.
- The biomarker showed 100% positive predictive value and 85% negative predictive value in validation.

## Abstract

Diagnosing systemic juvenile idiopathic arthritis (sJIA) poses significant challenges. Accumulating evidence has indicated that tRNA‐derived fragments (tRFs) play integral roles in the pathogenesis of numerous diseases. Plasma samples were collected from individuals diagnosed with sJIA and healthy controls (HCs) from two medical centers and divided into training and validation cohorts. Small‐RNA high‐throughput sequencing was employed to investigate the expression profiles of tRFs in the plasma of patients. Aberrantly expressed tRFs in sJIA were validated using quantitative reverse‐transcription PCR (qRT‐PCR). A total of 245 tRFs were differentially expressed in sJIA samples than in HC samples. Through qRT‐PCR validation, tRF‐30‐FP18LPMBQ4NK was identified as a potential biomarker. In the training cohort, plasma levels of tRF‐30‐FP18LPMBQ4NK were significantly higher in patients with sJIA than in HCs. Furthermore, the tRF‐30‐FP18LPMBQ4NK levels in patients in the active disease group were substantially higher than those in the inactive disease group. Additionally, the positive and negative predictive values of the selected tRF in the validation cohort reached 100% and 85%, respectively. Our results suggest that tRF‐30‐FP18LPMBQ4NK can be used as a promising biomarker candidate for sJIA and has the potential to aid in determining disease activity among patients with sJIA.