Reference interval and critical difference for canine serum fructosamine concentration

The purposes of the study were to obtain a reference interval and to calculate the critical difference between two analytical results for canine serum fructosamine concentration. To obtain a reference interval, the serum fructosamine concentration was measured in blood samples from 29 adult dogs after a 15-h fasting period. To calculate the critical difference, blood samples from 20 apparently clinically healthy dogs were collected once weekly for five consecutive weeks, and the total variance of the analytical results was divided into the component of variance between dogs (S2inter), the component of variance for weeks within dogs (S2intra) and the component of variance for measurements (S2anal), using nested analysis of variance. The critical difference was then calculated from S2intra and S2anal. The main conclusions are in summary: The reference interval for canine serum fructosamine concentration is 258.6-343.8 mumol/L, and the critical difference between two consecutive measurements on a week-to-week basis is 32.4 mumol/L. The critical difference may be used as a guideline to indicate potentially important changes in the serum fructosamine concentration, though the analytical results should not be assessed by the critical differences alone, but should also be compared to the corresponding reference intervals.