Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

9945
VLCMS
60036
Venlafaxine is significantly affected by reduced hepatic function, but only slightly by reduced renal
function. Average elimination half-lives are 5 hours for venlafaxine and 10 hours for
O-desmethylvenlafaxine, which are much shorter than many other antidepressants. For this reason,
extended release formulations are available. Time to peak serum concentration is 2 hours for the regular
product and 8 hours for the extended release product. Common toxicities are mild, including
drowsiness, dizziness, nausea, and headache.
Useful For: Monitoring serum concentration during therapy Evaluating potential toxicity The test may
also be used to evaluate patient compliance.
Interpretation: Most individuals display optimal response to venlafaxine when combined serum levels
of venlafaxine and O-desmethylvenlafaxine are between 195 and 400 ng/mL. Some individuals may
respond well outside of this range, or may display toxicity within the therapeutic range, thus interpretation
should include clinical evaluation. Risk of toxicity is increased with combined levels >1,000 ng/mL.
Therapeutic ranges are based on specimens drawn at trough (ie, immediately before the next dose).
Reference Values:
Venlafaxine + O-desmethylvenlafaxine: 195-400 ng/mL
Clinical References: 1. Wille SM, Cooreman SG, Neels HM, Lambert WE: Relevant issues in the
monitoring and toxicology of antidepressants. Crit Rev Clin Lab Sci 2008;45(1):25-89 2. Baumann P,
Hiemke G, Ulricj S, et al: The AGNP-TDM expert group consensus guidelines: therapeutic drug
monitoring in psychiatry. Pharmacopsychiatry 2004;37:243-265
Verhoeff's Elastic Tissue-Van Gieson's (V-ELVG) Stain for
Collagen and Elastic Fibers
Useful For: A stain for collagen, elastic fibers, and cardiac or skeletal muscle fibers.
Reference Values:
The laboratory will provide a pathology consultation and stained slide.
Very Long Chain Acyl-CoA Dehydrogenase Deficiency, Full
Gene Analysis
Clinical Information: Very long chain acyl-CoA dehydrogenase (VLCAD) deficiency is an
autosomal recessive disorder of mitochondrial fatty acid beta-oxidation. Mitochondrial beta-oxidation
plays a major role in energy production and VLCAD catalyzes the first step in the breakdown of fatty
acids that are 14 to 20 carbons long. VLCAD deficiency has a reported incidence of approximately 1 in
30,000 births and has a variable age of onset that is generally classified into 3 categories. Individuals with
the early-onset type present with cardiomyopathy, hypotonia, and hepatomegaly in the first months of life;
sudden death is also frequent. Individuals with the early-childhood onset type typically present with
hypoketotic hypoglycemia and hepatomegaly without cardiomyopathy. Individuals with the late-onset
type of VLCAD deficiency generally present after childhood with intermittent rhabdomyolysis and
muscle dysfunction that often manifests as muscle cramps and exercise intolerance. Review of clinical
features and biochemical analysis via plasma acylcarnitines, plasma fatty acid profile, urine organic acids,
and fibroblast fatty acid oxidation probe studies are recommended as laboratory evaluations for VLCAD
deficiency. Plasma and urine biochemical testing are not reliable for identifying all individuals with
VLCAD deficiency or confirming carrier status, as biochemical findings may normalize during periods of
good metabolic control. It is uncertain whether skin fibroblast analysis can identify carriers of VLCAD
deficiency. The diagnosis is confirmed by molecular testing. Mutations in the ACADVL gene are
responsible for VLCAD deficiency. Most mutations are family specific with the exception of the V283A
mutation (also reported in the literature as V243A). This mutation is estimated to account for 20% of
pathogenic alleles in patients identified by newborn screening. When this test is ordered, results of
biochemical assays should be included with the specimen as they are necessary for accurate interpretation
of the VLCAD sequence analysis.
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