Organic Acid Testing in Auto-Brewery Syndrome
An organic acid test will not show the classic abnormalities associated with inborn errors of metabolism in auto-brewery syndrome, as this condition involves exogenous ethanol production by gut microorganisms rather than a primary metabolic disorder.
Why Organic Acid Testing is Not Diagnostic for ABS
The American College of Medical Genetics and Genomics (ACMG) guidelines clearly define what organic acid testing detects: classic organic acidemias from inborn errors of amino acid metabolism, fatty acid oxidation disorders, energy metabolism defects, and other inherited metabolic conditions 1. Auto-brewery syndrome does not fit into any of these categories.
Key Distinctions
Auto-brewery syndrome is caused by microbial fermentation (typically Candida species or other fermenting yeasts/bacteria) that convert dietary carbohydrates into ethanol within the gastrointestinal tract 2, 3
Organic acid testing identifies genetic enzyme deficiencies that cause accumulation of specific metabolic intermediates like methylmalonic acid, glutaric acid, or branched-chain ketoacids 1
The ACMG's comprehensive table of recently described inborn errors with abnormal organic acid profiles does not include any fermentation-based syndromes 1, 4
What You Might See Instead
While organic acid testing won't diagnose ABS, you may observe:
Exogenous intoxication patterns if ethanol metabolites are present, though the ACMG notes that organic acid analysis can help distinguish exogenous intoxication from primary metabolic disorders 1
Secondary metabolic changes from chronic alcohol exposure (such as altered tricarboxylic acid cycle metabolites), but these are nonspecific 1
Normal organic acid profile is the most likely result, as the pathophysiology involves microbial ethanol production, not human metabolic enzyme defects 4
Correct Diagnostic Approach for ABS
The gold standard for diagnosing auto-brewery syndrome is a supervised carbohydrate challenge test with serial blood or breath ethanol measurements 3, 5:
- Admit the patient to a monitored setting with visitor restrictions to prevent alcohol intake 6
- Measure baseline blood ethanol level
- Administer oral glucose load
- Obtain serial ethanol measurements at 2,6,12, and 20 hours 6
- Elevated blood ethanol (often >100-300 mg/dL) without alcohol ingestion confirms the diagnosis 6, 7
Additional Confirmatory Testing
Stool or intestinal fluid analysis via endoscopy to identify fermenting organisms (commonly Candida glabrata, C. krusei, C. parapsilosis) with speciation and antifungal sensitivity 3, 7
Urinalysis may show positive glucose and ethanol with negative ethanol metabolites in bladder fermentation syndrome variant 2
Critical Clinical Pitfall
Do not order organic acid testing expecting to diagnose auto-brewery syndrome. The ACMG guidelines emphasize that interpretation must be based on overall metabolite patterns consistent with known inborn errors of metabolism 4. A normal organic acid test does not exclude ABS, and abnormal findings would more likely represent unrelated metabolic conditions or secondary effects rather than the syndrome itself 1.
The condition requires demonstration of endogenous ethanol production through challenge testing, not metabolic screening 3, 5.