Analytical Method Validation for Estimation of Neurotransmitters (Biogenic Monoamines) from Cerebrospinal Fluid Using High Performance Liquid Chromatography.

Biogenic amine neurotransmitters such as serotonin and dopamine are essential for signaling in both central and peripheral nervous system. Their metabolism is a multistep pathway and any defect in this results in alteration in metabolites of serotonin 5-Hydroxyindole acetic acid (5HIAA) and dopamine homovanillic acid (HVA) and 3-O-Methyl Dopa (3-OMD). Estimation of these metabolites in cerebrospinal fluid (CSF) assists in diagnosis of neurotransmitter defects. Their estimation is technically demanding and is currently available only in referral centers. We aimed to optimize a method for analysis of 5HIAA, HVA and 3-OMD. A high performance liquid chromatography (HPLC) method with electro chemical detector (ECD) was standardized for estimation. Analysis for method validation, reference range verification and clinical correlation was performed. Linearity obtained for 5-HIAA, HVA and 3-OMD was 65.35-2615.0 nmoles/l, 68.62-2745.0 nmoles/l and 236.5-4730.0 nmoles/l respectively. The coefficient of variation for internal quality controls ranged from 5 to 14% and the external proficiency testing samples (n = 16) were within peer group range. CSF metabolite levels of samples for reference range analysis overlapped with age matched ranges reported in literature. Among the 40 suspected patients analyzed for clinical testing four were found to have a neurotransmitter defect. These patients were then confirmed with molecular testing and clinical correlation. The method is validated and can be adapted in a clinical laboratory with analytical competence in HPLC.