Salivary IL-8 and Serum IL-6 as Biomarkers for Oral Potentially Malignant Disorders in Smokers and Never-Smokers

The goal of this observational study is to learn whether two inflammatory proteins, interleukin-8 (IL-8) measured in saliva and interleukin-6 (IL-6) measured in blood serum, can help distinguish adults with oral potentially malignant disorders (OPMDs), such as oral lichen planus and leukoplakia, from adults with healthy oral mucosa, and whether smoking changes these protein levels. The main questions it aims to answer are: * Do salivary IL-8 and serum IL-6 levels differ between people with OPMDs and healthy controls, and does this difference depend on smoking status? * How well do IL-8 and IL-6, alone or combined, discriminate people with OPMDs from healthy controls? Researchers compared healthy never-smokers, healthy current smokers, never-smokers with OPMDs, and current smokers with OPMDs. An additional exploratory group of current smokers with oral squamous cell carcinoma (OSCC) was compared with current smokers with OPMDs. Participants provided an unstimulated whole saliva sample and a blood sample at a single visit, and completed a clinical, periodontal, and tobacco-use assessment. No treatment was assigned as part of the study.

Inclusion Criteria: All participants: * Age 18 years or older * Written informed consent provided before enrollment * Smoking status classifiable as never-smoker or current smoker Healthy controls: * Clinically healthy oral mucosa * No clinical evidence or previous history of oral potentially malignant disorders (OPMDs) or oral cancer OPMD group: * Clinically identified oral lichen planus or oral leukoplakia, confirmed histopathologically * No definitive treatment of the lesion before biological-sample collection OSCC group (exploratory): * Histopathologically confirmed oral squamous cell carcinoma * Current smoker Exclusion Criteria: * Active oral infection unrelated to the study lesion * Recent major dental surgery or invasive dental procedure * Active or recent systemic infection * Uncontrolled diabetes mellitus * Major systemic inflammatory or autoimmune disease * Clinically significant salivary gland dysfunction * Current systemic treatment likely to substantially affect inflammatory cytokine concentrations (e.g., systemic corticosteroids or immunomodulatory agents) * Essential clinical data or smoking-status classification unavailable * Biological samples insufficient, unsuitable for analysis, or failing predefined laboratory quality-control criteria