C5-OH Acylcarnitine, Quantitative, Urine
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The differential diagnosis of an isolated elevation of 3-hydroxyisovaleryl-/2-methyl-3-hydroxy acylcarnitine (C5-OH) in plasma or (newborn screening) blood spots includes the following disorders:
-3-Methylcrotonyl-CoA carboxylase deficiency (common name: 3-methylcrotonylglycinuria), either infantile or maternal
-3-Hydroxy 3-methylglutaryl-(HMG)-CoA lyase deficiency
-2-Methyl 3-hydroxybutyryl-CoA dehydrogenase deficiency, 3-methylglutaconic aciduria type I, and biotinidase deficiency or holocarboxylase deficiency
Confirmatory and diagnostic testing are necessary to differentiate these clinical entities. This test can be useful in differentiating patients with 3-methylcrotonylglycinuria and with 3-methylglutaconic aciduria as they typically excrete larger amounts of C5-OH in urine compared to patients with the other diagnoses.
The American College of Medical Genetics (ACMG) newborn screening work group published diagnostic algorithms for the follow-up of infants who had positive newborn screening results. For more information, see URL: http://www.acmg.net.
Evaluation of patients with an abnormal newborn screen showing elevations of C5-OH
Preliminary data showed that an elevated excretion in urine and concentration in plasma of C5-OH can be the only biochemical abnormalities in patients with 3-methylcrotonylglycinuria.
Contact Mayo Medical Laboratories for assistance in test interpretation and additional testing options.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
The results of urine acylcarnitines are not informative when the patient is receiving L-carnitine supplements.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
<2.93 millimoles/mole creatinine
Clinical References Provides recommendations for further in-depth reading of a clinical nature
Wolfe LA, Finegold DN, Vockley J, et al: Potential misdiagnosis of 3-methylcrotonyl-coenzyme A carboxylase deficiency associated with absent or trace urinary 3-methylcrotonylglycine. Pediatrics 2007 Nov;120(5):e1335-1340