Diagnostic value of reticulocyte indices for the assessment of the iron status of cats with chronic kidney disease

BACKGROUND: Reticulocyte indices have been suggested as alternatives to transferrin saturation (TSAT) for iron status assessment in humans and dogs but they have not been evaluated thoroughly in cats. OBJECTIVES: To assess the value of the reticulocyte indices for the diagnosis of iron deficiency in cats with chronic kidney disease (CKD) and chronic hematuria associated with subcutaneous ureteral bypasses (SUBs). ANIMALS: Sixty-four cats: 16 healthy, 14 CKD without SUB, and 34 CKD with SUB. METHODS: Prospective observational cross-sectional study of cats presented for routine nephrology visits. Primary outcomes included assessment of the diagnostic values of erythrocyte indices (mean corpuscular volume, hemoglobin, and hemoglobin concentration: MCV, MCH, and MCHC) and reticulocyte indices (mean corpuscular volume, MCVr; corpuscular hemoglobin, CHr), using TSAT as reference. RESULTS: Iron deficiency was diagnosed in 9/64 cats (14%). A receiver-operating characteristic curve analysis yielded a moderate discriminatory value for CHr in this diagnosis: area under the curve [AUC] = .75 (95% confidence interval, 0.48-0.89); P = .006; sensitivity 67%, specificity 82% for a cutoff of 15.9 pg. This compared favorably to MCVr (AUC = .63; P = .29), MCV (AUC = .58; P = .45), MCH (AUC = .64; P = .19), and MCHC (AUC = .7; P = .03). CONCLUSION AND CLINICAL IMPORTANCE: CHr added moderate value to the diagnosis of iron deficiency in cats with CKD.