C4 Acylcarnitine, Quantitative, Random, Urine
Use
Evaluation of patients with abnormal newborn screens showing elevations of iso-/butyrylcarnitine to aid in the differential diagnosis of short‑chain acyl‑CoA dehydrogenase and isobutyryl‑CoA dehydrogenase deficiencies. Elevated iso‑/butyrylcarnitine (C4) in plasma or newborn screening blood spots is due to either SCAD (short‑chain acyl‑CoA dehydrogenase) deficiency or IBD (isobutyryl‑CoA dehydrogenase) deficiency. Urine C4 results can distinguish between SCAD deficiency, which results in normal C4 in urine, and IBD deficiency, which results in elevated C4 in urine.
Special Instructions
This second‑tier test is used specifically to evaluate a newborn screening elevation of iso‑/butyrylcarnitine and must not be ordered with either C5‑OH Acylcarnitine, Quantitative, Random, Urine (C5OHU) or C5‑DC Acylcarnitine, Quantitative, Random, Urine (C5DCU). Patient's age, family history, clinical condition (asymptomatic or acute episode), diet, and drug therapy information is requested but not required. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.
Limitations
The results of urine acylcarnitines are typically not informative when the patient is receiving L‑carnitine supplements. Almost all patients with isobutyryl‑CoA dehydrogenase deficiency excrete an abnormal amount of iso‑/butyrylcarnitine (C4) in their urine. Some, but not all, affected individuals also excrete elevated levels of isobutyrylglycine. Conversely, patients with short‑chain acyl‑CoA dehydrogenase deficiency can have a normal excretion of C4.
New York Approved
Methodology
Mass Spectrometry (LC‑MS/MS)
Biomarkers
LOINC Codes
- 53111-1
- 53111-1
- 59462-2
- 18771-6
Result Turnaround Time
2-5 days
Related Documents
For more information, please review the documents below
Specimen
Urine
Volume
5 mL
Minimum Volume
1 mL
Container
Plastic, 10 mL urine tube
Collection Instructions
Collect a random urine specimen. Freeze specimen immediately.
Patient Preparation
Discontinue L‑carnitine supplementation at least 72 hours before collection, if clinically feasible.
Stability Requirements
| Temperature | Period |
|---|---|
| Refrigerated | 24 hours |
| Frozen | 7 days |