a Salivary Cell-free RNA Liquid Biopsy Model for Non-invasive Diagnosis in Sjögren's Disease

This observational study will evaluate SjoTrace, a salivary cell-free RNA (cfRNA)-based liquid biopsy approach for Sjögren's disease (SjD). SjD is an autoimmune disease that often affects the salivary glands and causes dryness symptoms, but diagnosis can be challenging because sicca symptoms may also occur in people without SjD.

In this study, saliva samples will be collected from participants with SjD and from non-SjD sicca control participants as part of an observational research protocol. Salivary cfRNA profiles will be analyzed to identify RNA features associated with SjD. Machine-learning methods will be used to develop and evaluate a cfRNA-based diagnostic score.

The study will also explore whether salivary cfRNA signals are related to clinical features of SjD, including immune-related laboratory findings and salivary gland pathology. In addition, transcriptomic datasets from salivary gland tissue, including bulk RNA sequencing, single-cell RNA sequencing, and spatial transcriptomic data, will be analyzed to investigate the possible tissue and cellular sources of disease-associated cfRNA signals.

This study does not assign participants to any treatment or intervention. All clinical care decisions will be made by the participants' regular health care providers. The research is intended to assess the diagnostic and biological value of salivary cfRNA as a non-invasive tool for SjD evaluation.

Inclusion criteria

SjD group:

• Aged 18-65 years
• Fulfilled the 2016 ACR/EULAR classification criteria for Sjögren's disease
• Newly diagnosed or previously diagnosed with complete diagnostic evidence available
• Willing to provide clinical data and saliva samples
• Provided written informed consent

Non-SjD sicca control group:

• Aged 18-65 years
• Frequency-matched with the case group by sex and age
• No personal or family history of autoimmune diseases
• No persistent symptoms suggestive of SjD (e.g., dry mouth or dry eyes), with physical examination and necessary laboratory test results within normal limits
• Willing to provide clinical data and saliva samples
• Provided written informed consent

Exclusion criteria

• Malignant tumors or severe active infections
• Pregnancy or lactation
• Use of biologics or potent immunosuppressive therapy within the past 3 months that could significantly alter study indicators (patients included due to strict clinical necessity will be recorded and utilized for sensitivity analysis)
• Severe hepatic or renal impairment, or other diseases that significantly interfere with cfRNA detection
• Failure to meet the standardized oral status, fasting, or sampling timing requirements prior to collection, with resampling being impossible
• Incomplete clinical data
• Substandard collection, preservation, or quality control of saliva or labial gland tissue samples
• Any other conditions deemed unsuitable for participation by the investigator