Evaluation of urinary biomarkers for azotaemic chronic kidney disease in cats

OBJECTIVESEvaluation of urine albumin:creatinine ratio, urine cystatin C:creatinine ratio, urine protein:creatinine ratio and urine specific gravity as screening tests for azotaemic chronic kidney disease in cats. METHODSA group of cats over eight years old were defined as either (i) healthy non-azotaemic (n=40) if they had serum creatinine concentration <153 mu mol/L and no history of apparent disease or (2) having azotaemic chronic kidney disease (n=12) if they had serum creatinine concentration >153 mu mol/L with urine specific gravity <1035. Urine albumin:creatinine ratio, urine cystatin C:creatinine ratio, urine protein:creatinine ratio and urine specific gravity were compared between the two groups. RESULTSUrine cystatin C:creatinine ratio was significantly lower in cats with azotaemic chronic kidney disease than that in healthy cats [37 (14, 43)x10(-6)versus 139 (63, 247)x10(-6); P=0011]. Urine specific gravity was also significantly lower in the azotaemic chronic kidney disease group than that in the healthy group [1022 (1017, 1028) versus 1043 (1034, >1050); P<0001]. Urine albumin:creatinine ratio and urine protein:creatinine ratio were not significantly different between the groups (P=0075 and P=0965, respectively). CLINICAL SIGNIFICANCEUrine cystatin C:creatinine ratio and urine specific gravity were significantly lower in cats with azotaemic chronic kidney disease than that in healthy cats; however, neither biomarker was an adequate sole screening test for azotaemic chronic kidney disease.