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Unit Code 88830:
C5-OH Acylcarnitine, Quantitative, Urine

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Useful For

Evaluation of patients with an abnormal newborn screen showing

elevations of C5-OH

Clinical Information

The differential diagnosis of an isolated elevation of 3-hydroxy

isovalerylcarnitine (C5-OH) in newborn screening blood spots

includes 3-methylcrotonyl-CoA carboxylase deficiency (common

name: 3-methylcrotonylglycinuria), either infantile or maternal; 

3-hydroxy 3-methylglutaryl-(HMG)-CoA lyase deficiency;

beta-ketothiolase deficiency; 2-methyl 3-hydroxy butyryl-CoA

dehydrogenase deficiency; 3-methylglutaconic aciduria type I;

and, in some cases, biotinidase deficiency and holocarboxylase

deficiency. Follow-up confirmatory and diagnostic testing is

necessary to differentiate the different clinical entities. Preliminary

data show that this test can be of some utility in the differential

diagnosis of infants who have a positive newborn screening

result for C5-OH.

Reference Values

<2.93 millimoles/mole creatinine

Interpretation

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.

Cautions

The results of urine acylcarnitines are not informative when

the patient is receiving L-carnitine supplements.

Clinical Reference

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; in press

Key