R & D Assignment – Kinjal Ghia – DT204/ VANILLYLMANDELIC ACID [VMA]

 Vanillylmandelic acid (VMA) is one of the metabolites of the catecholamines adrenaline (epinephrine) and noradrenaline (norepinephrine). This test measures the amount of VMA that is excreted into the urine, typically over a 24-hour period, to detect excess catecholamine production.metabolitescatecholamines Definition

Disease  VMA is usually present in the urine in small fluctuating amounts that only increase appreciably during and shortly after the body is exposed to stress. Neuroblastomas, phaeochromocytomas, and other neuroendocrine tumours, however, can produce large amounts of catecholamines, resulting in greatly increased concentrations of the hormones and their metabolites.phaeochromocytomasneuroendocrine  To help diagnose or rule out a neuroblastoma, phaeochromocytoma, or other neuroendocrine tumour; to monitor the effectiveness of treatment.phaeochromocytomaneuroendocrine

 It is present in high amount in urine which makes its analysis simple. Spectrophotometric methods for determination of VMA is superseded by gas or liquid chromatography based methods, using mainly mass spectrometric detection, which is highly specific.  Liquid Chromatography:  It is separation method in which stationary phase is packed into a tube and is based on differential distribution of solutes between a liquid mobile phase and a stationary phase.  HPLC- High Performance liquid chromatography. Small diameter particle are used in stationary phase. Method & Principle

 Liquid chromatography-Mass spectrometry  It is more difficult to interface LC with MS as analytes are dissolved in liquid rather than gas, which causes difficulties in the vacuum pumping system of MS. Once the compound can be dissolved in liquid it can be applied to HPLC- MS system.  The reason that you need to collect urine over a 24-hour period is because the amount of VMA excreted in the urine changes during the course of a day. By collecting all urine for 24 hours, the amount of VMA measured can be averaged over the entire day and will give a better indication of whether levels are increased or not.  In 24 hour urine collection 25ml of 50% acetic acid is added as a preservative to adjust urine pH and patient age and total volume is recorded Method & Principle

Commercial Test  ELISA kit is designed for in vitro quantitative measurement of VMA in urine.  ELISA- Enzyme Linked Immunosorbent Assay based on VMA coated on a microtitre well and that present in urine for the monoclonal antibody.  There are no home or self test kit available for this particular test.

Reference Range The following normal values are the amount of the substance found in the urine over a 24-hour period:

Controls  No standard cut off levels between positive and negative VMA.  Recommended cut off level of 25 µg/mg creatinine  Individual laboratories use a level of 2 standard deviations and above that age specific mean to identify reanalysis  On reanalysis 3 standard deviations above the mean confirms the need for diagnostic evaluation

References 1. ple ple 2. Burtis C A, Bruns D E, Catecholamines and Serotonin ch-26, Tietz Fundamentals of Clinical chemistry and Molecular Diagnostics. 7 th Edition Elsevier Saunders, USA, pp catalog/clinical+and+interpretive/ Stjameshospital.adam.com/content.aspx?productid=117&pid=1&gid= ofessional/page2 ofessional/page2 6. emedicine.medscape.com/article/ overview#aw2aab6b2 7. Google Images