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PubMed This is a summary of 13 peer-reviewed journal articles Updated
Medical Genetics

Biology & Diagnosis: How IVA is Confirmed

At a Glance

A positive newborn screen for Isovaleric Acidemia (IVA) is not a final diagnosis. Maternal use of certain antibiotics or skin creams can cause false positives. Doctors use a urine organic acid test and genetic sequencing of the IVD gene to definitively confirm if your baby has the condition.

Understanding the biology behind Isovaleric Acidemia (IVA) can help transform a frightening newborn screening (NBS) report into a manageable medical plan. At its core, IVA is a condition where the body cannot properly “clean up” the waste products created when it breaks down a specific protein building block called leucine [1].

The Biology of the Breakdown

Every time your baby eats protein, their body breaks it down into amino acids, including one called leucine [1]. Under normal circumstances, an enzyme (a specialized protein) called isovaleryl-CoA dehydrogenase (IVD) acts as a gatekeeper, processing leucine into energy [1][2].

In a child with IVA, the IVD gene—the “instruction manual” for making this enzyme—contains a mutation [1]. This means the enzyme is either missing or doesn’t work well enough. As a result, the process gets “backed up,” and a toxic substance called isovaleric acid builds up in the blood and tissues [1].

Why the Screen Might Be a “False Positive”

It is vital to know that an initial “positive” result on a newborn screen is not the same as a final diagnosis. The screening test looks for a marker called C5-acylcarnitine [3]. However, several external factors can cause this marker to be high even if the baby does not have IVA:

  • Medication Exposure: Certain antibiotics (like pivmecillinam) or prodrugs contain a substance called pivalate [4]. If a mother takes these medications during late pregnancy or breastfeeding, the baby’s body converts the pivalate into pivaloylcarnitine [5].
  • Skin Products: Some skin creams, balms, or nipple creams contain neopentanoate (often listed as isostearyl neopentanoate) [4].
  • The “Mimic” Effect: Biologically, pivaloylcarnitine is an isobaric isomer of the IVA marker—meaning they have the exact same molecular weight [3]. Most standard screening machines cannot tell the difference between the “false” medication marker and the “true” IVA marker [5][6].

Confirming the Diagnosis

Because of the risk of false positives, doctors use a “gold standard” process to confirm if a baby truly has IVA:

  1. Urine Organic Acid Test: This is often the most important follow-up test. It looks for a substance called isovalerylglycine (IVG) [7]. Unlike the blood marker, IVG is highly specific to IVA. It will not be elevated if the result was caused by antibiotics or skin creams [7][8].
  2. Genetic Sequencing: Specialists will look at the IVD gene itself. This is the definitive way to confirm the diagnosis and determine the severity of the condition [9][10].
  3. Identifying the “Mild” Variant: Genetic testing frequently identifies a specific change called the p.Ala311Val (also known as c.932C>T) variant [1][2]. This is widely recognized as a “mild” or “attenuated” form of IVA. Babies with this variant often have an excellent prognosis and may never experience a metabolic crisis, sometimes requiring only minimal dietary changes [11][12].

By combining these tests, your metabolic team can distinguish between a temporary “mimic” and a lifelong condition, ensuring your baby receives exactly the level of care they need [10][13].

Common questions in this guide

What causes a false positive for Isovaleric Acidemia on a newborn screen?
A false positive can occur if the mother used certain antibiotics or skin creams containing pivalate or neopentanoate during late pregnancy or breastfeeding. These substances create a marker in the blood that looks identical to the IVA marker on standard screening machines.
How do doctors confirm if my baby actually has Isovaleric Acidemia?
Specialists use a urine organic acid test to look for isovalerylglycine, a substance unique to true IVA. They will also perform genetic sequencing on the IVD gene to definitively confirm the diagnosis and determine its severity.
What does the p.Ala311Val variant mean on an IVA genetic test?
This specific genetic change is recognized as a mild or attenuated form of Isovaleric Acidemia. Babies with this variant typically have an excellent prognosis, are less likely to experience a metabolic crisis, and may only require minimal dietary changes.
What is the IVD gene and how does it relate to IVA?
The IVD gene acts as an instruction manual for making an enzyme that helps process leucine, a protein building block. In children with Isovaleric Acidemia, a mutation in this gene causes the enzyme to be missing or less effective, causing toxic acids to build up.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Does my baby's laboratory report show high levels of isovalerylglycine (IVG) in the urine, or just C5-carnitine in the blood?
  2. 2.Could the use of specific antibiotics (like pivmecillinam) or skin creams (containing neopentanoate) have caused a false positive for my child?
  3. 3.Has genetic sequencing of the IVD gene been performed to confirm the diagnosis?
  4. 4.Does the genetic report show the p.Ala311Val (c.932C>T) variant, and what does that mean for my child's daily management?
  5. 5.If this is a 'false positive' from medication exposure, does my baby need temporary carnitine supplements to restore their levels?

Questions For You

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References

References (13)
  1. 1

    Clinical and neurocognitive outcome in symptomatic isovaleric acidemia.

    Grünert SC, Wendel U, Lindner M, et al.

    Orphanet journal of rare diseases 2012; (7()):9 doi:10.1186/1750-1172-7-9.

    PMID: 22277694
  2. 2

    Practical Considerations for the Diagnosis and Management of Isovaleryl-CoA-Dehydrogenase Deficiency (Isovaleric Acidemia): Systematic Search and Review and Expert Opinions.

    Thimm E, Riederer A, Vockley J, et al.

    International journal of neonatal screening 2025; (11(4)) doi:10.3390/ijns11040092.

    PMID: 41133704
  3. 3

    A Simple Flow Injection Analysis-Tandem Mass Spectrometry Method to Reduce False Positives of C5-Acylcarnitines Due to Pivaloylcarnitine Using Reference Ions.

    Hattori T, Notsu Y, Tanaka M, et al.

    Children (Basel, Switzerland) 2022; (9(5)) doi:10.3390/children9050694.

    PMID: 35626871
  4. 4

    Hypocarnitinemia Observed in an Infant Treated with Short-Term Administration of Antibiotic Containing Pivalic Acid.

    Nakazaki K, Ogawa E, Ishige M, et al.

    The Tohoku journal of experimental medicine 2018; (244(4)):279-282 doi:10.1620/tjem.244.279.

    PMID: 29628457
  5. 5

    Neonatal screening for isovaleric aciduria: Reducing the increasingly high false-positive rate in Germany.

    Murko S, Aseman AD, Reinhardt F, et al.

    JIMD reports 2023; (64(1)):114-120 doi:10.1002/jmd2.12345.

    PMID: 36636590
  6. 6

    Introduction of a Simple Second Tier Screening Test for C5 Isobars in Dried Blood Spots: Reducing the False Positive Rate for Isovaleric Acidaemia in Expanded Newborn Screening.

    Carling RS, Burden D, Hutton I, et al.

    JIMD reports 2018; (38()):75-80 doi:10.1007/8904_2017_33.

    PMID: 28631226
  7. 7

    Genotype and phenotype characterization in a Spanish cohort with isovaleric acidemia.

    Couce ML, Aldamiz-Echevarría L, Bueno MA, et al.

    Journal of human genetics 2017; (62(3)):355-360 doi:10.1038/jhg.2016.144.

    PMID: 27904153
  8. 8

    Isovaleric aciduria identified by newborn screening: Strategies to predict disease severity and stratify treatment.

    Mütze U, Henze L, Schröter J, et al.

    Journal of inherited metabolic disease 2023; (46(6)):1063-1077 doi:10.1002/jimd.12653.

    PMID: 37429829
  9. 9

    Characterization of variants of uncertain significance in isovaleryl-CoA dehydrogenase identified through newborn screening: An approach for faster analysis.

    D'Annibale OM, Koppes EA, Alodaib AN, et al.

    Molecular genetics and metabolism 2021; (134(1-2)):29-36 doi:10.1016/j.ymgme.2021.08.012.

    PMID: 34535384
  10. 10

    Prenatal Diagnosis of Isovaleric Acidemia From Amniotic Fluid Using Genetic and Biochemical Approaches.

    Ding S, Liang L, Qiu W, et al.

    Frontiers in genetics 2022; (13()):898860 doi:10.3389/fgene.2022.898860.

    PMID: 35846131
  11. 11

    Newborn screening and disease variants predict neurological outcome in isovaleric aciduria.

    Mütze U, Henze L, Gleich F, et al.

    Journal of inherited metabolic disease 2021; (44(4)):857-870 doi:10.1002/jimd.12364.

    PMID: 33496032
  12. 12

    Newborn screening algorithm distinguishing potential symptomatic isovaleric acidemia from asymptomatic newborns.

    Rock R, Rock O, Daas S, et al.

    Journal of inherited metabolic disease 2025; (48(1)):e12800 doi:10.1002/jimd.12800.

    PMID: 39318119
  13. 13

    Molecular analysis using targeted next generation DNA sequencing and clinical spectrum of Mexican patients with isovaleric acidemia.

    Ibarra-González I, Fernández-Lainez C, Guillén-López S, et al.

    Clinica chimica acta; international journal of clinical chemistry 2020; (501()):216-221 doi:10.1016/j.cca.2019.10.041.

    PMID: 31707166

This page explains newborn screening and diagnostic testing for Isovaleric Acidemia for educational purposes only. Always consult your child's metabolic specialist for accurate interpretation of screening and diagnostic test results.

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