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Company
Immunology & Autoimmune
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Currently under review
Pending specialist review and validation.
C4DC is a specific acylcarnitine measured in blood that represents two isomers, methylmalonylcarnitine and succinylcarnitine. It reflects how your body processes certain amino acids and odd chain fats through the propionate pathway inside mitochondria, a process that relies on vitamin B12 and several enzymes.
This test is typically performed by tandem mass spectrometry as part of an acylcarnitine profile on plasma or a dried blood spot. It helps evaluate inherited metabolic conditions and some acquired problems that affect energy production and organic acid handling.
Doctors use C4DC to help investigate conditions such as methylmalonic acidemia, propionic acidemia, and disorders of cobalamin metabolism, and to follow up abnormal newborn screening results. It can also be useful when symptoms suggest a metabolic problem or vitamin B12 deficiency, such as poor feeding, vomiting, lethargy, developmental concerns, or unexplained anemia and neurologic changes.
C4DC results can guide the urgency of care and the need for confirmatory testing, including urine organic acids, plasma methylmalonic acid, homocysteine, vitamin B12 level, and genetic studies. It can also assist with monitoring response to treatments such as vitamin B12, carnitine, diet changes, and infection control. While informative, this marker is interpreted together with your history, examination, and other laboratory findings.
A higher C4DC value can suggest a bottleneck in the propionate pathway, which may occur in inherited metabolic disorders or with low or functionally impaired vitamin B12. The degree of elevation, your age, current health, and other test results shape the interpretation. Your clinician may repeat the test and pair it with targeted studies to clarify the cause and determine next steps.
A value within the age appropriate range is reassuring but does not completely rule out disease if symptoms persist. A lower value is rarely worrisome on its own and can reflect low carnitine stores or preanalytic factors. If results are unexpected, your care team will discuss whether to adjust diet or supplements, check vitamin B12 status, review medications, and consider genetic or metabolic evaluations.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Newborns and young infants have changing metabolism as feeding begins, so C4DC levels can shift in the first days and weeks of life. Results are interpreted using age specific reference intervals and clinical context.
Fever, infection, poor intake, or prolonged fasting increase metabolic stress and can raise acylcarnitines, including C4DC. Drawing the sample when you are acutely ill can influence interpretation.
Low vitamin B12 intake or absorption, or recent exposure to nitrous oxide anesthesia, can impair B12 dependent enzymes and elevate C4DC. Maternal vitamin status also affects infant results.
Reduced kidney function can lead to accumulation of related metabolites and may contribute to higher C4DC readings. Your team may review kidney markers when interpreting results.
Low carnitine stores may blunt acylcarnitine formation, while carnitine supplementation can change the acylcarnitine pattern. Measuring free and total carnitine alongside C4DC can be helpful.
Dried blood spots and plasma are both used, but preanalytic issues like delayed drying, heat exposure, or hemolysis can alter acylcarnitine measurements. Proper collection and storage support reliable results.
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