Triglyceride Reference Values for a Meal Challenge Test to Assist Diagnosis and Management of Canine Hyperlipidemia
Centre for Companion Animal Health, Uni. of Queensland
Hyperlipidemia in dogs is associated with clinical disorders, including recurrent seizures and acute pancreatitis. Dietary therapy is typically recommended for management of hyperlipidemia and a standardized method for evaluating efficacy of dietary management in controlling postprandial triglyceride concentrations is needed. This study aimed to determine reference values using 95% tolerance intervals for 24 hour fasting and postprandial peak triglyceride concentrations for healthy dogs after a standard meal, to assist in diagnosis and management of hyperlipidemia.
Twelve (6 male, 6 female) lean, healthy, neutered, mixed-breed dogs were studied. Dogs were fed a dry commercial maintenance diet (fat 31%ME, CHO 45%ME, protein 24%ME, fiber 2g/100kcal) for 3 weeks. After a 24 hour fast, plasma triglyceride concentrations were measured at -1, -0.08, 1, 2, 3, 4, 5, 6, 9, and 12 hours after a meal (median amount eaten: 127 kcal/kg0.75). Raw and log transformed data were tested for normal distribution using Kolmogorov-Smirnov test and for outliers using Grubb's test. To determine the most appropriate time for blood sampling (the time most closely associated with highest postprandial triglyceride concentration), Spearman's correlation coefficients, associated 95% confidence intervals (CI) and p values were calculated to assess correlations in raw data between postprandial peak triglyceride and triglyceride concentrations at each time point. Tolerance intervals were calculated with log-transformed data using a parametric method.
One dog had a postprandial peak triglyceride concentration 44% higher than the next highest dog; however its fasting value was toward the low end of the tolerance interval. It was found to be an outlier using Grubb's test and was not included in calculation of tolerance intervals. Triglyceride concentration at 6 hours after ingestion of the standard meal had the closest association with postprandial peak triglyceride concentration with and without this dog (r=0.93 and 0.91, respectively; p<0.01; 95% CI: 0.77 to 0.98 and 0.68 to 0.98, respectively). The tolerance interval for postprandial peak triglyceride concentration was 49 to 191 mg/dL (0.54 to 2.11 mmol/L). The tolerance interval for triglyceride concentration 6 hours after eating was 35 to 176 mg/dL (0.38 to 1.94 mmol/L). The tolerance interval for 24 hour fasted triglyceride concentrations sampled 5 minutes prior to a meal was 14 to 91 mg/dL (0.15 to 1.00 mmol/L). In 50% of the dogs, triglyceride concentrations did not return to baseline by 12 hours after eating.
In conclusion, measurement of both fasting and postprandial peak triglyceride concentrations after a standard meal are important for detecting hyperlipidemia and for evaluating responses to therapeutic diets, because fasting concentrations alone are not likely to be predictive of postprandial peak concentrations. The reference values determined in this study can be applied in a meal challenge test to dogs which have been fasted 24 hours, fed the same standard meal, and sampled 5 minutes prior to the meal and 6 hours after eating.