When it comes to diagnosing and monitoring the health of dogs, understanding the role of various metabolic markers is crucial. One such marker, cobalamin (Vitamin B12), plays a key role in various bodily functions, including nerve and red blood cell health. However, limited data on the reference intervals (RIs) for cobalamin and related metabolites, like homocysteine and methylmalonic acid (MMA), has left veterinarians with a challenge: how to properly interpret these markers in healthy dogs.

A new study led by Anna-Lena Proksch and colleagues set out to fill this gap by establishing RIs for these vital markers in healthy adult dogs and examining how age and sex may impact these values. The research is significant, as it helps fine-tune veterinary diagnostics and ensures more accurate interpretations of metabolic health in dogs.

Study Methodology

The study involved 120 healthy dogs aged 1-10 years. Researchers used advanced techniques like chemiluminescence immunoassay and liquid chromatography/tandem mass spectrometry to measure cobalamin, homocysteine, serum methylmalonic acid (sMMA), and urinary methylmalonic acid-to-creatinine (uMMA:crea) ratios. These markers were examined for any abnormal readings and analyzed for variations based on age and sex.

Key Findings

The research revealed some important findings:

1. Age-Related Decrease in Cobalamin Levels
   As dogs age, their cobalamin concentrations tend to decrease significantly. This was the only metabolic marker that showed a clear, age-related variation in the study. This highlights the importance of adjusting expectations and reference intervals for older dogs when assessing their metabolic health.

2. Sex-Specific Differences in uMMA:crea Ratios
   One of the most surprising findings was the significant difference in uMMA:crea ratios between intact male dogs and other groups. Intact males had much higher uMMA:crea ratios (median 13.5 mg/g) compared to females and neutered males (median 2.5 mg/g). This led to the recommendation of sex-specific reference intervals for uMMA:crea, where intact male dogs have an upper limit of 58.9 mg/g, while females and neutered males have a limit of 5.2 mg/g.

3. Outliers and Health Re-Evaluation
   The study also re-evaluated dogs with outlying data after 9-15 months. Of the 12 dogs with abnormal uMMA:crea ratios, 64% developed chronic gastrointestinal signs, while the remaining 36% remained healthy. This suggests that dogs with abnormal results may be at risk of developing gastrointestinal issues, underscoring the importance of continued monitoring.

Clinical Significance

The findings of this study are critical for veterinary practitioners. First and foremost, the research reinforces the need to interpret metabolic markers, like uMMA:crea, with caution, especially in intact male dogs. The significant variability in uMMA:crea ratios among sexes means that using a universal reference interval could lead to misinterpretation of results.

Moreover, the age-related decrease in cobalamin levels highlights the importance of considering a dog's age when assessing its metabolic health. For older dogs, veterinarians should be mindful of the potential for lower cobalamin levels, which could influence diagnostic decisions and treatment plans.

This study on the effects of age and sex on metabolic markers like cobalamin, homocysteine, and methylmalonic acid in dogs provides valuable insights for veterinarians. By establishing accurate reference intervals for these markers and understanding how factors like age and sex influence them, veterinary professionals can make more informed decisions when diagnosing and monitoring their canine patients. The research also paves the way for more personalized, precise healthcare for dogs, ensuring that all pets, regardless of age or sex, receive the best possible care.

Read full article here: https://onlinelibrary.wiley.com/doi/10.1111/jvim.17250