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PubMed This is a summary of 21 peer-reviewed journal articles Updated
Medical Genetics · Very Long-Chain Acyl-CoA Dehydrogenase Deficiency

Starting Your Journey: Understanding the Initial Screen

At a Glance

A positive VLCADD newborn screen is not a diagnosis; it may reflect a false alarm, carrier status, or VLCADD. Prompt follow-up testing is needed, and the metabolic team should give exact feeding instructions to prevent prolonged fasting while results are pending.

Receiving an abnormal result from your baby’s newborn screening can feel like the world has suddenly shifted. It is common for parents to experience a profound sense of shock, anxiety, and distress when they are told their newborn might have a serious metabolic condition [1][2]. You may feel overwhelmed by the sudden influx of medical information while you are still adjusting to life with a new baby. Please know that these feelings are a normal response to a very difficult situation [3].

This guide is designed to help you navigate this period of uncertainty. It will explain what this screening result means, how the diagnostic process works, and how your new care team will support you and your baby.

Understanding the Screening Result

The most important thing to know right now is that a positive newborn screen is not a final diagnosis [4][5]. Think of the newborn screen as a high-sensitivity smoke alarm: it is designed to go off even if there is just a hint of a problem so that doctors can investigate quickly [6].

Because the screen is so sensitive, many babies who “fail” the initial screen turn out to be perfectly healthy. In various studies of babies with an abnormal screen for VLCADD, the results showed a wide range of outcomes [7][8]:

  • False Positives: Sometimes, factors like the baby’s weight at the time of the test or how long it had been since their last feeding can cause a temporary “blip” in the results [9].
  • Carriers: Many babies are found to be carriers, meaning they carry one copy of the gene for VLCADD. Carriers are generally asymptomatic, though finding one variant alone does not completely rule out a second undetected variant or a biochemical disorder [4][10].
  • True Positives: Some babies are confirmed to have VLCADD. Even among these children, the severity can vary greatly—some may have a milder form that requires only simple precautions [11][12].

What is VLCADD?

VLCADD stands for Very Long-Chain Acyl-CoA Dehydrogenase Deficiency. In plain language, it means the body has trouble breaking down a specific type of fat to create energy [13].

Usually, our bodies burn sugar (glucose) for energy first. When that runs out—such as during long periods without food (fasting) or when we are sick—the body switches to burning fats [14][15]. A baby with VLCADD is missing or has a low level of an enzyme (a protein that helps with chemical reactions) needed to turn “very long-chain” fats into fuel [13]. Because they cannot use these fats properly, their body may run out of energy, and unused fat products can build up in the body [15].

VLCADD is rare. While estimates vary depending on the population and the specific screening methods used, a frequently cited incidence is approximately 1 per 50,000 to 100,000 newborns, though it can be more common in certain populations [16][17].

Your Metabolic Care Team

Because this condition involves how the body uses fuel (metabolism), you will work with a specialized metabolic care team. This team is there to provide expertise and support as you move from a “positive screen” to a clear answer. Key members include:

  • Metabolic Geneticist: This is a doctor who specializes in inherited metabolic disorders. They will oversee your baby’s diagnostic testing, interpret the results, and create a long-term care plan if one is needed [4].
  • Metabolic Dietitian: Since VLCADD is managed primarily through how and what a baby eats, the dietitian is a vital partner. They will help you manage feeding schedules and, if necessary, specific dietary changes to ensure your baby always has enough energy [18][12].

Immediate Next Steps

The diagnostic process involves repeat blood tests and sometimes genetic testing to look closely at the baby’s DNA [19][20]. While you wait for these results, your team will give you critical “interim” instructions.

Do not wait for a routine appointment. You must contact the metabolic or newborn screening team promptly. The most urgent instruction is to avoid prolonged fasting—this means ensuring the baby feeds at exact, frequent intervals dictated by your doctor, even through the night [18][20].

If your baby is difficult to feed, unusually sleepy, limp, or ill, do not wait for test results or a scheduled visit. Seek urgent medical care immediately and tell the providers your baby has an abnormal newborn screen for a metabolic disorder [21].

Common questions in this guide

Does a positive VLCADD newborn screen mean my baby has the disorder?
No. A newborn screen is designed to be highly sensitive and is not a final diagnosis; an abnormal result can be a false positive, indicate carrier status, or lead to a confirmed diagnosis. Follow-up testing with the metabolic team is needed to know what the result means.
What is VLCADD in plain language?
VLCADD is a rare inherited condition in which the body has trouble breaking down very long-chain fats for energy. The problem can become more important during fasting or illness, when the body needs to use fat as fuel.
What tests are usually done after an abnormal VLCADD screen?
Doctors may repeat blood tests and may order genetic testing to examine the baby’s DNA. A metabolic geneticist will interpret the results with the rest of the clinical information and explain whether more evaluation is needed.
How often should my baby feed while VLCADD is being checked?
Ask the metabolic or newborn-screening team for the exact maximum time between feeds and follow that plan, including overnight. Do not create a fasting plan on your own; contact the team promptly if you have not received feeding instructions.
What symptoms mean my baby needs urgent medical care?
Seek urgent medical care if your baby is difficult to feed, unusually sleepy, limp, or ill. Tell the clinicians that the baby had an abnormal newborn screen for a metabolic disorder.
Could my baby simply be a VLCADD carrier?
Yes, some babies with an abnormal screen are found to carry one VLCADD gene variant and are generally healthy without symptoms. However, finding one variant does not always rule out a second undetected variant or a biochemical disorder, so confirmatory testing is important.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What were the specific levels on my baby's newborn screen, and how do they compare to the typical cutoff for VLCADD?
  2. 2.Given these initial results, what is the likelihood that this is a false positive or that my baby is just a carrier?
  3. 3.What specific confirmatory tests are being ordered now, and how long will the results take?
  4. 4.Until we have a final diagnosis, what is the exact maximum number of hours my baby can safely go between feedings?
  5. 5.Who is our main point of contact on the metabolic team if my baby feeds poorly or seems unwell today?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (21)
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    Prevalence and predictors of parental distress at the communication of positivity at newborn screening for metabolic diseases: an Italian longitudinal study.

    Bani M, Russo S, Gasperini S, et al.

    BMJ paediatrics open 2024; (8(1)) doi:10.1136/bmjpo-2024-003103.

    PMID: 39667953
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    Absorbing it all: A meta-ethnography of parents' unfolding experiences of newborn screening.

    White AL, Boardman F, McNiven A, et al.

    Social science & medicine (1982) 2021; (287()):114367 doi:10.1016/j.socscimed.2021.114367.

    PMID: 34534781
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    Psychological Impact on Parents of an Inconclusive Diagnosis Following Newborn Bloodspot Screening for Cystic Fibrosis: A Qualitative Study.

    Johnson F, Southern KW, Ulph F

    International journal of neonatal screening 2019; (5(2)):23 doi:10.3390/ijns5020023.

    PMID: 33072982
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    Four Years' Experience in the Diagnosis of Very Long-Chain Acyl-CoA Dehydrogenase Deficiency in Infants Detected in Three Spanish Newborn Screening Centers.

    Merinero B, Alcaide P, Martín-Hernández E, et al.

    JIMD reports 2018; (39()):63-74 doi:10.1007/8904_2017_40.

    PMID: 28755359
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    Parental psychosocial outcomes after a positive newborn screen for a lysosomal storage disorder.

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    Molecular genetics and metabolism 2025; (146(3)):109235 doi:10.1016/j.ymgme.2025.109235.

    PMID: 41005062
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    Rhabdomyolysis in a neonate due to very long chain acyl CoA dehydrogenase deficiency.

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    Molecular genetics and metabolism reports 2015; (3()):39-41 doi:10.1016/j.ymgmr.2015.03.003.

    PMID: 26937394
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    Newborn screening follow-up for very long-chain acyl-CoA dehydrogenase deficiency in Colorado: Working towards a standardized protocol.

    Crenshaw MM, D'Annibale OM, Schechter A, et al.

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    PMID: 40215729
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    A Review of Newborn Screening for VLCADD: The Wisconsin Experience.

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    Characteristic Findings of Infants with Transient Elevation of Acylcarnitines in Neonatal Screening and Neonatal Weight Loss.

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    Recurrent ACADVL molecular findings in individuals with a positive newborn screen for very long chain acyl-coA dehydrogenase (VLCAD) deficiency in the United States.

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    The Newborn Screening Paradox: Sensitivity vs. Overdiagnosis in VLCAD Deficiency.

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    PMID: 26453363
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    Proposal for an individualized dietary strategy in patients with very long-chain acyl-CoA dehydrogenase deficiency.

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    Journal of inherited metabolic disease 2019; (42(1)):159-168 doi:10.1002/jimd.12037.

    PMID: 30740737
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    Very-Long-Chain Acyl-CoA Dehydrogenase Deficiency: Family Impact and Perspectives.

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    International journal of neonatal screening 2023; (9(4)) doi:10.3390/ijns9040053.

    PMID: 37873844
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    ACADVL Deep Sequencing in a Case Study: Beyond the Common c.848T>C Pathogenic Variant.

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    Recent Advances in the Pathophysiology of Fatty Acid Oxidation Defects: Secondary Alterations of Bioenergetics and Mitochondrial Calcium Homeostasis Caused by the Accumulating Fatty Acids.

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    Insights from the Newborn Screening Program for Very Long-Chain Acyl-CoA Dehydrogenase (VLCAD) Deficiency in Kuwait.

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This page is for informational purposes only and is not medical advice. It cannot replace your baby’s metabolic team; follow their feeding instructions and seek urgent care if your baby feeds poorly or seems unwell.

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