DWQA QuestionsCategory: QuestionsFast or Fed Adult Acylcarnitine profile
Lori asked 3 years ago
To rule out suspected MTP/LCHAD in an adult patient born after the initiation of newborn screening, should the acylcarnitine profile blood test be completed with the patient in a well-fed or fasted state? The patient presented to an outpatient lab following an 8-hour fast for the blood draw. But the lab turned the patient away and insisted the test be completed an hour after eating a full meal. If the patient in is a period of relative wellness the day prior to the test, and intends to endure only an 8-hour fast to avoid a further increase in symptoms, should he/she eat breakfast before the blood draw? Thank you in advance for your input.
INFORM Physician
replied 3 years ago

Lori, A fasting test will definitely be more sensitive. Without knowing clinical details, I wouldn’t advocate going beyond 8 hrs. Mild disease can still be missed and if the acylcarnitine profile is normal and suspicion is strong, then a free fatty acid profile is often positive. Finally, consider gene testing. In Vitae is offering a free panel that includes both TFP subunit genes. I’d recommend referral to a metabolic specialist to coordinate the testing as there are many nuances to consider. I hope this helps. Dr. Vockley

Lori Pool
replied 3 years ago

Thank you for your input! This is very helpful! Clinical suspicion does seem to be strong. Also, the patient had whole genome sequencing that revealed a homozygous HADHB frameshift defect of unknown significance. We’ll pursue independent validation with Vitae as you suggest to rule out sequencing error and hope that the bloodwork provides some additional answers. I believe the referral to the metabolic specialist is pending subject to the acylcarnitine profile and urine organic acid results. We’ll ask about the free fatty acid profile as well! You’re the best. Thanks for being here for us!