Example Registered Report Abstract - Clinical Application
Title
Magnetic Resonance Spectroscopy for Detecting Metabolic Alterations in Major Depressive Disorder: A Registered Report
Introduction
Major Depressive Disorder (MDD) affects approximately 7% of the adult population and remains difficult to diagnose objectively. Previous studies suggest neurochemical abnormalities in MDD patients that could be detected through Magnetic Resonance Spectroscopy (MRS). However, findings have been inconsistent due to methodological variations and small sample sizes. This registered report outlines a confirmatory study designed to identify reliable metabolic biomarkers in the anterior cingulate cortex (ACC) that distinguish MDD patients from healthy controls.
Hypothesis
We hypothesize that MDD patients will show significantly reduced GABA/Cr ratios and elevated Glu/Cr ratios in the ACC compared to matched healthy controls, with effect sizes of d≥0.75 for GABA/Cr and d≥0.65 for Glu/Cr.
Preliminary Data
We present two complementary approaches to justify our effect size estimates:
Option 1: Exploratory Study Results In our pilot study (n=12 MDD patients, n=12 controls), we measured six metabolites (NAA, Cho, Cr, mI, GABA, Glu) in the ACC using MEGA-PRESS at 3T. GABA/Cr ratios showed the largest difference (21.7% reduction in MDD vs. controls, p=0.022, d=0.82), followed by Glu/Cr ratios (16.3% increase in MDD, p=0.048, d=0.67). Other metabolites showed smaller, non-significant differences (p>0.05).
Option 2: Literature-Based Effect Size Our systematic review of 15 MRS studies in MDD (cumulative n=423 MDD patients, n=379 controls) revealed consistent GABA deficits in the ACC with pooled effect sizes ranging from d=0.65-0.89. Meta-regression showed larger effects in medication-naïve patients (d=0.78, 95% CI [0.63-0.93]). Glutamate findings were more heterogeneous but suggested moderate elevations (d=0.62, 95% CI [0.46-0.78]) in ACC.
Study Protocol
Study Design and Population
This confirmatory cross-sectional study will include 42 medication-naïve MDD patients (diagnosed using DSM-5 criteria, HAMD-17 score ≥18) and 42 age- and sex-matched healthy controls. Exclusion criteria include other psychiatric disorders, neurological disease, substance use disorder, and MRI contraindications.
MR Acquisition Protocol
All participants will undergo 3T MRS (Siemens MAGNETOM Prisma) with:
- MEGA-PRESS sequence for GABA (TE=68ms, TR=2000ms, 256 averages)
- PRESS sequence for other metabolites (TE=30ms, TR=2000ms, 128 averages)
- Voxel placement: 2×2×2cm³ in the dorsal ACC
- Additional T1-weighted imaging for tissue composition correction
Clinical Assessments
All participants will complete:
- HAMD-17 and BDI-II for depression severity
- STAI for anxiety symptoms
- Structured clinical interview (SCID-5)
- Demographic and medical history questionnaires
Statistical Analysis Plan
Primary Outcomes
- GABA/Cr ratio differences between MDD and control groups
- Glu/Cr ratio differences between MDD and control groups
Secondary Outcomes
- Correlation between GABA/Cr and depression severity
- Correlation between Glu/Cr and depression severity
- Exploratory analysis of other metabolites (NAA, Cho, mI)
Sample Size Justification
Based on our pilot data and literature review, we estimate effect sizes of d=0.75 for GABA/Cr and d=0.65 for Glu/Cr. Power analysis indicates that 42 subjects per group will provide 90% power to detect both effects at α=0.025 (Bonferroni-corrected for two primary outcomes).
Statistical Methods
- Independent samples t-tests for between-group comparisons (with Bonferroni correction)
- ANCOVA with age, sex, and gray matter fraction as covariates
- Pearson correlations for metabolite-symptom associations
- ROC analysis to determine diagnostic utility