Salivary RNA biomarkers for autism assessment in children: clinical promise, validation gaps and practical relevance for developmental disability pathways

Objectives To evaluate whether salivary RNA biomarker studies in children offer meaningful value for autism-related developmental assessment rather than merely detecting case-control molecular differences.Methods A focused critical narrative review, with reporting informed by the Scale for the Assessment of Narrative Review Articles (SANRA), used targeted PubMed and Europe PMC searches supplemented by Google Scholar and citation tracking. Studies were prioritised through title, abstract, and full-text reading without duplicate screening. Eligible studies were peer-reviewed human studies in children examining salivary RNA markers relevant to autism assessment, developmental comparison, or practical interpretation. Mixed salivary RNA-microbial panels were included only when directly relevant. The literature was synthesised qualitatively with emphasis on comparator structure, validation, developmental relevance, and interpretability.Results Exploratory studies repeatedly detected salivary RNA differences, whereas assessment-oriented multifeature panels tested against developmentally relevant comparators showed the strongest but still limited findings beyond initial discovery samples. Narrower miRNA-only models were less robust. Studies of longitudinal change, subgroup heterogeneity, and broader transcriptomic context added biological insight but did not establish dependable usefulness for real-world assessment.Conclusions Salivary RNA biomarkers should be regarded as research-stage adjuncts, not established tools for developmental assessment. Progress will depend on validation beyond initial discovery samples, including genuinely independent replication in clinically relevant cohorts, clearer workflow standardisation, and evidence of added value within assessment pathways.