Diagnosis & Understanding Your Lab Reports

Reading your child’s lab reports can feel like trying to translate a foreign language. However, for Dicarboxylic Aminoaciduria, the diagnosis relies on a few specific “clues” in the chemistry of the urine and the DNA ^[1]. By knowing exactly which tests were run and what the numbers mean, you can ensure your child has received a complete and accurate evaluation.

The Two Most Important Tests

Doctors usually order two types of urine tests when they suspect a metabolic difference. While they sound similar, they look for very different things:

1. Quantitative Urine Amino Acids (The “Must-Have” Test): This test measures the exact amount of different amino acids in the urine ^[1]. In Dicarboxylic Aminoaciduria, you will see a significant “spike” in two specific ones: glutamate and aspartate ^[1][2]. These elevations are typically “isolated,” meaning the rest of the amino acids should look normal.
2. Urine Organic Acids (The “Rule-Out” Test): This test is often done to make sure the child does not have Dicarboxylic Aciduria (a different, more serious condition related to fat burning) ^[3][4]. If this test comes back normal, it confirms that the “spill” is limited to amino acids and is not a metabolic emergency ^[5].

Deciphering the Numbers

When you look at the results for a Quantitative Urine Amino Acid test, look for these two markers:

• Glutamate (Glutamic Acid): Will be significantly higher than the reference range ^[1].
• Aspartate (Aspartic Acid): Will also be significantly elevated ^[1].

In many cases of Dicarboxylic Aminoaciduria, these levels are 10 times higher (or more) than the normal limit because the kidneys are not “recycling” them at all ^[1].

Genetic Confirmation: The SLC1A1 Gene and Inheritance

While urine tests show what is happening, genetic testing explains why. The definitive way to confirm this diagnosis is through a genetic test for the SLC1A1 gene ^[6].

• Autosomal Recessive Inheritance: True Dicarboxylic Aminoaciduria requires biallelic mutations, meaning a child inherits two mutated copies of the gene (one from each parent) ^[1]. This means there is a 25% chance for each current or future sibling to also have the condition. You should strongly discuss sibling testing with your geneticist to ensure any neurodevelopmental traits in other children are monitored early.
• Carrier Status: If a child has only one mutation (heterozygous), they are a carrier. They may spill small amounts of amino acids, but they do not have the full disorder ^[7].

Completeness Checklist for Parents

To ensure your child’s diagnostic workup is thorough, check your lab folder for the following:

• [ ] Quantitative Urine Amino Acids: Does it specifically list “Glutamate” and “Aspartate” as elevated? ^[1]
• [ ] Urine Organic Acids: Was this run to rule out fatty acid oxidation disorders? ^[3]
• [ ] Kidney Health Baseline: Did the doctor check for sugar (glucose) or protein in the urine? (This helps prove the “spill” is just SLC1A1 and not a broader kidney issue like Fanconi Syndrome) ^[8].
• [ ] SLC1A1 Genetic Test: Has DNA been collected to confirm the specific transporter defect? ^[6]

If all these boxes are checked and the only findings are elevated glutamate and aspartate, you are likely looking at a classic case of Dicarboxylic Aminoaciduria ^[1][9].