Peer-reviewed veterinary case report
Algal supplement caused false positive urine test for storage disease
By Sewell, Adrian C & Pankraz, Alexander·Published in Veterinary clinical pathology·2013·Department of Pediatrics, Germany·View original on PubMed →
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Original publication title: Interference of an algal nutritional supplement with a urinary metabolic screening test for glycosaminoglycans in a dog suspected to have a storage disease.
- Species:
- dog
Plain-English summary
A 3-year-old English Cocker Spaniel tested positive for a urinary screening test for glycosaminoglycans (GAG), which is often a sign of a storage disease called mucopolysaccharidosis (MPS). However, the dog showed no other symptoms of MPS. Further testing revealed that the positive result was likely due to an algal nutritional supplement in its dog food, which caused a false-positive reading. When a healthy dog was fed the same food, it also showed similar abnormal results. The Cocker Spaniel's owner was advised to stop the supplement, but no follow-up testing was done.
People also search for: dog urinary test positive for GAG · Cocker Spaniel storage disease symptoms · false positive MPS test in dogs
Abstract
The finding of excess urinary glycosaminoglycans (GAG) is the first step in the laboratory diagnosis of mucopolysaccharidosis (MPS). Urinary screening tests are based upon the binding of GAG to dimethylmethylene blue. Alternatively, paper spot tests using toluidine blue are used in human and veterinary laboratory medicine. Positive samples undergo GAG isolation for subsequent characterization. Here, we describe a 3-year-old English Cocker Spaniel with a positive urinary GAG test, but without other clinical signs of MPS. Urine samples were strongly positive with the dimethylmethylene blue test, and isolated GAG subjected to electrophoresis on cellulose acetate revealed a band co-migrating with dermatan sulfate. However, the isolated GAG were resistant to digestion with chondroitinase ABC, suggesting that the band did not represent dermatan sulfate. This was confirmed by mobility of the isolated GAG different from dermatan sulfate on agarose gel electrophoresis. MPS types VI and VII were excluded by enzyme assay. To test the hypothesis of a nutritional source, a healthy control dog was fed the same dog food as the index case. His urine showed a comparable abnormal GAG screening test and electrophoretic pattern. In addition, the analysis of an algal supplement present in the administered dog food showed a similar electrophoretic GAG pattern. The Cocker Spaniel was not available for further testing after withdrawal of the supplement. Algae contain highly sulfated fucans and galactans, and it appears that commercial dog food containing such algal, and possibly other, supplements can give rise to false-positive urinary MPS screening tests.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/24320782/