Relationship between FGF 23, SDMA, Urea, Creatinine and Phosphate in Relation to Feline Chronic Kidney Disease

SIMPLE SUMMARY: Chronic kidney disease (CKD) is the most frequent metabolic disorder affecting geriatric cats, and is a major cause of mortality among this species. Due to its progressive nature and non-specific clinical signs, an effort is being made to discover new, more efficient biomarkers of glomerular filtration for the timely diagnosis of renal insufficiency. Symmetric dimethylarginine (SDMA) and fibroblast growth factor 23 (FGF 23) are promising new markers currently of interest in veterinary medicine. This study discusses the relationship between SDMA, FGF 23 and previously used indicators of kidney function, mainly creatinine, urea and phosphate, to establish their efficacy in a clinical setting. An increase in FGF 23 in CKD patients compared to healthy cats has been recognized, despite the lack of an evident correlation of FGF 23 with other analyzed markers. ABSTRACT: Chronic kidney disease (CKD) is a common diagnosis in older cats, and its prevalence increases with age. Conventional indirect biomarkers of glomerular filtration rate (GFR) have their limitations, and are not efficient in detecting early decreases in glomerular filtration rate. Recently, symmetric dimethylarginine (SDMA) concentrations have been proposed as a novel biomarker of GFR for the early detection of CKD. This study discusses the relationship between SDMA, FGF 23 and previously used indicators of kidney function, mainly creatinine, urea and phosphate. Ninety-nine cats were included in this study. Based on their SDMA values, 48 cats had CKD and the remaining 51 cats were used as a healthy control group. Serum of these cats was assayed for creatinine, urea and phosphate concentrations as well as FGF 23 values, and correlations between them were evaluated. Cats with CKD had higher FGF 23 concentrations than healthy cats, and no correlation was found between FGF 23 and SDMA, nor between FGF 23 and phosphate. On the other hand, phosphate strongly correlated with SDMA, urea and creatinine, making it a possible independent factor of CKD progression.