Plasma 5-HIAA Emerges as a High-Accuracy Biomarker for Major Depressive Disorder
核心洞察
A validated DLLME-LC-MS/MS method quantified plasma 5-hydroxyindoleacetic acid (5-HIAA) (搜索) with 95.1% extraction recovery and a 5 ng/mL lower limit of quantification.
Plasma 5-HIAA was significantly elevated in 17 patients with major depressive disorder (搜索) (25.73 ng/mL) versus 20 healthy controls (17.35 ng/mL), a roughly 48% increase.
ROC analysis yielded an area under the curve of 0.985, with 88.20% sensitivity and 100% specificity at a 21.93 ng/mL cutoff.
A newly validated bioanalytical method has identified plasma 5-hydroxyindoleacetic acid (5-HIAA) (搜索) as a promising quantitative biomarker for major depressive disorder (搜索) (MDD), achieving near-perfect diagnostic discrimination in a case-control study. Researchers developed a dispersive liquid-liquid microextraction (DLLME) method coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) and applied it to 37 participants, reporting an area under the curve (AUC) of 0.985 for distinguishing depressed patients from healthy controls.
The study, conducted in accordance with the Declaration of Helsinki and approved by the Institutional Review Board of the Faculty of Medicine, Al-Azhar University, Damietta branch (approval no. DFM-IRB 00012367-25-08-056), enrolled 17 patients diagnosed with MDD according to DSM-5 criteria and 20 age- and sex-matched healthy controls.
A Green, Derivatization-Free Analytical Method
The analytical approach centered on a DLLME procedure optimized using a Box-Behnken design with four independent variables: disperser solvent volume (acetonitrile, 500–1500 µL), extraction solvent volume (ethyl acetate, 50–300 µL), sample pH (2.0–7.0), and centrifugation time (3–9 min). Analysis of variance confirmed a highly significant second-order polynomial model (F = 38.23, p < 0.0001), with pH exerting the strongest influence on extraction recovery (F = 91.16, p < 0.0001), followed closely by extraction solvent volume (F = 86.51, p < 0.0001).
The pH dependence reflects the ionization state of 5-HIAA, which possesses a carboxylic acid functional group (pKa ~ 4.5). At acidic pH, protonation suppresses ionization and enhances partitioning into the nonpolar organic extraction phase. Numerical optimization identified optimal conditions of disperser volume 1100 µL, extraction volume 300 µL, pH 2.0, and centrifugation time 5.5 min, yielding a predicted recovery of 95.26%. Experimental verification produced a mean extraction recovery of 95.1 ± 2.3% (CV 2.4%).
The method employed a stable isotope-labeled internal standard (5-HIAA-d5) and was validated according to ICH M10 bioanalytical method validation guidelines using a surrogate matrix (charcoal-stripped plasma) approach. Calibration curves across 5–1000 ng/mL demonstrated excellent linearity (r² = 0.9997), with a lower limit of quantification (LLOQ) of 5 ng/mL at 7.5% CV.
Elevated 5-HIAA in Depression
Plasma 5-HIAA concentrations were significantly elevated in MDD patients compared to healthy controls. The MDD group exhibited mean levels of 25.73 ± 3.60 ng/mL (range 19.06–32.49 ng/mL), while controls demonstrated mean levels of 17.35 ± 1.70 ng/mL (range 13.99–20.79 ng/mL) — an approximately 48% elevation among depressed patients. An independent t-test revealed a highly significant difference (t = -8.79, p < 0.001) with a very large effect size (Cohen's d = 3.059).
This finding of elevated peripheral 5-HIAA contrasts with the well-established observation of reduced 5-HIAA concentrations in cerebrospinal fluid, which has been documented as a marker of diminished central serotonergic neurotransmission and associated with suicide risk in depression. The divergent central and peripheral patterns suggest distinct regulatory mechanisms governing serotonergic metabolism in different biological matrices.
Diagnostic Performance
Receiver operating characteristic (ROC) curve analysis evaluated the diagnostic utility of plasma 5-HIAA for discriminating between MDD patients and healthy controls. The analysis yielded an AUC of 0.985 (95% CI: 0.959–1.000, p < 0.001), indicating excellent diagnostic discrimination. The optimal cutoff value determined using Youden's index was 21.93 ng/mL.
At this threshold, the method demonstrated sensitivity of 88.20%, correctly identifying 15 of 17 MDD patients, and perfect specificity of 100%, with no false positives among the 20 control subjects. The positive predictive value was 100%, while the negative predictive value was 90.90%. Overall diagnostic accuracy was 94.60%, representing correct classification of 35 of 37 participants.
Correlation with Depression Severity
Beyond diagnostic classification, plasma 5-HIAA levels demonstrated significant correlation with depression severity as quantified by the Hamilton Depression Rating Scale (HAM-D). In the MDD group, Pearson correlation analysis revealed a strong positive association between 5-HIAA concentrations and HAM-D scores (r = 0.791, 95% CI: 0.500–0.921, p < 0.001), with the coefficient of determination (r² = 0.625) indicating that 62.5% of variance in depression severity scores was explained by plasma 5-HIAA levels.
In contrast, the control group exhibited no significant correlation (r = 0.089, p = 0.710), indicating that the association is disease-specific rather than a general relationship present across all individuals. The MDD group had a mean HAM-D score of 21.1 ± 3.9, confirming moderate to severe depression, compared to 4.3 ± 1.6 in controls (p < 0.001, Cohen's d = 5.751).
Study Limitations
Several limitations warrant consideration. The cross-sectional study design prevents establishment of causal relationships or temporal dynamics of 5-HIAA changes relative to disease course. Single time-point measurements cannot address whether elevated 5-HIAA represents a trait marker present before depression onset or a state marker that emerges with active disease.
The authors recommend future longitudinal studies examining 5-HIAA trajectories during antidepressant treatment, investigation in larger and more diverse cohorts, multi-center validation studies to establish reference ranges and standardized cutoff values, and mechanistic investigations to elucidate the biological pathways linking peripheral 5-HIAA elevation to central serotonergic dysfunction.