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The effect of feeding, storage and anticoagulant on feline serum cystatin C
L F E Ghys1, D Paepe1, H P Lefebvre2
1Department of Medicine and Clinical Biology of Small Animals, Faculty of Veterinary Medicine, Ghent University, 133 Salisburylaan, B-9820 Merelbeke, Belgium.
Insights
Serum cystatin C (sCysC) is a promising marker for feline chronic kidney disease (CKD). While not affected by age, breed, or sex, daily variations and storage impact its accuracy. Fasting is not required, but prolonged freezing is not recommended.
Area of Science:
- Veterinary Medicine
- Biochemistry
- Nephrology
Background:
- Serum cystatin C (sCysC) shows potential for early chronic kidney disease (CKD) detection in cats.
- Unlike serum creatinine (sCr), sCysC is unaffected by feline age, breed, or sex, necessitating further validation.
- Understanding biological and storage factors is crucial for reliable sCysC use in feline diagnostics.
Purpose of the Study:
- To assess the influence of food intake and circadian rhythm on feline sCysC levels.
- To determine the stability of sCysC under various storage conditions.
- To compare plasma cystatin C (pCysC) concentrations with serum cystatin C (sCysC) in cats.
Main Methods:
- A crossover study in 10 healthy cats investigated feeding and diurnal variations.
- Storage stability was tested at room temperature and different freezing points (-20°C, -72°C).
- Comparisons of pCysC and sCysC were made in healthy cats and cats with CKD.
Main Results:
- A significant diurnal variation in sCysC was observed.
- Pre- and postprandial sCysC and sCr levels did not change significantly.
- sCysC increased with room temperature storage and decreased after prolonged freezing (≥5 months).
- Plasma CysC was significantly lower than sCysC, indicating they are not directly comparable.
Conclusions:
- Fasting is not mandatory before evaluating sCysC and sCr in cats.
- Serum samples are stable under routine storage conditions.
- Prolonged freezing (over 5 months) is not recommended for sCysC samples due to decreased concentrations.
- Plasma and serum CysC values cannot be used interchangeably in feline diagnostics.
Abstract:
Serum cystatin C (sCysC) is a possible marker for early detection of chronic kidney disease (CKD) in cats. In contrast with serum creatinine (sCr), feline sCysC is not affected by age, breed or sex. However, further biological and clinical validation is required. The objectives of this study were: (1) to investigate if food intake and circadian rhythm affect feline sCysC; (2) to determine the stability of sCysC under different storage conditions, and (3) to investigate if plasma concentrations of CysC (pCysC) differed from sCysC. A crossover study with 10 healthy laboratory cats fed the same commercial dry food was performed to study the influence of feeding and diurnal variation. Storage effects and comparison of pCysC with sCysC were determined using healthy cats (n = 3 and n = 10, respectively) and cats with CKD (n= 4 and n = 17, respectively). A significant daily sCysC variation was seen. Pre- and postprandial sCysC and sCr concentrations did not change significantly. Serum CysC significantly increased during storage at room temperature. After freezing, sCysC significantly decreased after 5 and 12 months at both -20 °C and -72 °C. Plasma CysC was significantly lower than sCysC. These findings suggest that it is not mandatory to fast cats before evaluation of sCysC and sCr. Samples were stable during routinely used storage conditions. Based on these findings, freezing for more than 5 months is not recommended, although additional studies are required to evaluate the clinical relevance of decreased sCysC after prolonged storage. Plasma and serum CysC cannot be compared directly.
