BACKGROUND AND HYPOTHESIS: The pathogenesis of tardive dyskinesia (TD) remains unclear, involving multiple biological pathways. This study aimed to explore biomarkers of TD through untargeted metabolomics for the early identification of TD. STUDY DESIGN: This study recruited 84 schizophrenia (SZ) patients with TD and 160 SZ patients without TD. TD diagnosis was based on the Schooler-Kane criteria, and the severity of TD and psychiatric symptoms were assessed using the Abnormal Involuntary Movement Scale and the Positive and Negative Syndrome Scale. Fasting blood samples were collected from all patients and subjected to untargeted metabolomics analysis using Ultra-high-performance liquid chromatography-high resolution mass spectrometry, allowing for the quantification and profiling of 699 metabolites. Data were analyzed with orthogonal partial least squares discriminant analysis, and receiver-operating characteristic curves. STUDY RESULTS: In TD, 57 metabolites exhibited significant changes (variable importance of projection >
1, false discovery rate-adjusted P <
.05), primarily involving amino acids and lipids. These changes predominantly affected the phenylalanine, tyrosine, and tryptophan pathway (impact = 0.5, P = .0252), as well as the phenylalanine metabolism pathway (impact = 0.36, P = .0498). N-Acetyl-l-phenylalanine (B = 2.249, t = 4.56, P <
.001, 95% CI, 1.302-3.286) and Succinylcarnitine (AcCa(4:0-DC)) (B = 1.009, t = 3.07, P = .002, 95% CI, 0.362-1.656) are negatively related to the total abnormal involuntary movement scale score. Additionally, 5 differential metabolites had area under the curve (AUC) values greater than 0.7 for diagnosing TD, with the combined diagnostic capability exceeding 0.8 (AUC = 0.817, 95% CI, 0.759-0.875). CONCLUSIONS: In TD, disruptions in amino acid and lipid metabolism were predominantly observed. Amino acids and lipid metabolites may be involved in the development of TD. Additionally, a biomarker panel composed of amino acids and lipids can be used for the differential diagnosis of TD.