Plasma formiminoglutamic acid shows potential as a functional marker of folate deficiency in cats and dogs: development and validation of a liquid chromatography-tandem mass spectrometry method.

OBJECTIVE

To evaluate formiminoglutamic acid (FIGLU) as a potential marker of folate deficiency in cats and dogs by (1) establishing a liquid chromatography-tandem mass spectrometry (LC-MS-MS) method for the quantification of FIGLU in feline and canine plasma, and (2) reporting plasma FIGLU concentrations in clinically normal cats and dogs.

METHODS

An LC-MS-MS method for FIGLU quantitation was developed and analytically validated. Clinically normal cats and dogs were prospectively included for plasma FIGLU and serum folate measurement (via LC-MS-MS and chemiluminescence immunoassay, respectively). Statistical analysis was performed to assess for correlations between plasma FIGLU and serum folate concentrations.

RESULTS

Accuracy, precision, linearity, and recovery experiments met validation requirements. Dilution integrity experiments did not meet the acceptance criteria, potentially due to ion suppression effects. Plasma FIGLU ranged from 4.5 to 21.0 ng/mL in 11 clinically normal dogs and 9.1 to 57.0 ng/mL in 10 clinically normal cats. There was no evidence of a correlation between serum folate and plasma FIGLU concentrations in clinically normal cats and dogs.

CONCLUSIONS

The amount of FIGLU present in the plasma of clinically normal cats and dogs is quantifiable via LC-MS-MS, and reference interval determination of plasma FIGLU is therefore feasible. Future studies should include both normofolatemic and hypofolatemic animals to assess the correlation between serum folate and plasma FIGLU and to determine the optimal serum folate cutoff limit.

CLINICAL RELEVANCE: Plasma FIGLU shows promise as a practical research tool and a potential functional marker of folate availability in cats and dogs.