Platform
Company
Immunology & Autoimmune
Review status
Currently under review
Pending specialist review and validation.
This test measures the ratio of two acylcarnitines in the blood, C14:1 and C16. Acylcarnitines are small molecules that help move fatty acids into mitochondria, where they are broken down for energy. By comparing these two related molecules, the test provides a snapshot of how well certain fat metabolism pathways are working.
It is commonly used as part of newborn screening or follow-up testing when there is concern for very long-chain acyl-CoA dehydrogenase deficiency, often called VLCAD deficiency. The ratio is unitless and is typically measured by tandem mass spectrometry on a small blood sample.
Energy from fat becomes especially important during illness or fasting. If VLCAD, a key enzyme for breaking down long-chain fats, is not working properly, the body may struggle to maintain normal energy levels. An abnormal C14:1/C16 ratio can point toward reduced activity in this pathway and prompt timely evaluation.
Clinicians use this test to help identify or rule out VLCAD deficiency in newborns flagged by screening, and in children or adults with symptoms such as low blood sugar without ketones, muscle pain, exercise intolerance, or episodes of muscle breakdown. Recognizing a fatty acid oxidation disorder early can guide diet, activity, and emergency care plans that reduce risks during stress or illness.
Your result is interpreted alongside other acylcarnitines, your symptoms, and any recent illnesses or supplements. A result that suggests a fatty acid oxidation issue does not by itself confirm a diagnosis. Doctors often repeat testing, check a full plasma acylcarnitine profile, and may order genetic testing of the ACADVL gene to clarify the picture.
If results point toward VLCAD deficiency, your care team will discuss nutrition strategies, sick-day plans, and when to seek urgent care. If results are normal but symptoms continue, your clinician may look for other causes of muscle or energy problems. Always review your medications, supplements, and recent health events with your provider, since these can influence the ratio.
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.
In newborns and infants, timing of collection relative to birth and feeding can affect acylcarnitine patterns. Samples taken very soon after delivery or during prolonged fasting may look different from those collected after regular feeding.
Fever, infection, dehydration, or strenuous exercise can shift fatty acid metabolism and transiently alter acylcarnitine ratios. Results during or shortly after illness should be interpreted with caution and may require repeat testing when well.
Carnitine supplements, medium-chain triglyceride formulas, and total parenteral nutrition can change acylcarnitine profiles. Tell your clinician about all nutrition products and supplements before testing.
Dried blood spot versus plasma testing and delays in processing can influence measured acylcarnitines. Proper collection, storage, and timely analysis help ensure a reliable ratio.
Some medicines and special diets that modify fat metabolism may impact the ratio. Provide a complete list of medications, including over-the-counter products and herbal remedies, to your healthcare team.
For newborn results, maternal conditions, diet, and supplements around delivery can influence the baby’s acylcarnitine pattern. Confirmatory testing is often done after the immediate newborn period.
References