Objective—To investigate serum calcium-phosphorus concentration product (sCaPP) as a predictor of mortality rate in dogs with chronic kidney disease (CKD).
Design—Retrospective case-control study.
Animals—31 dogs with definitive CKD and 35 apparently healthy dogs.
Procedures—All dogs had been referred for nephrological consultation between December 2008 and December 2010. Dogs with CKD had stable disease for ≥ 3 months. On the basis of glomerular filtration rate < 60 mL/min/m2, 13 of the 35 apparently healthy dogs were subsequently classified as having early CKD. Disease stage among dogs was determined on the basis of plasma creatinine concentration as follows: stage 1, < 123.7 μmol/L (n = 13), stage 2, 123.7 to 176.8 μmol/L (7); stage 3, 185.6 to 442 μmol/L (13); or stage 4, > 442 μmol/L (11). For each dog, serum concentrations of ionized and total calcium and phosphorus were evaluated once; the latter 2 variables were used to determine sCaPP.
Results—The sCaPP differed significantly between the 22 healthy dogs and dogs with stage 3 or stage 4 CKD. The proportion of dogs with sCaPP > 70 mg2/dL2 increased with stage of disease. Mortality rate among the 24 dogs with sCaPP > 70 mg2/dL2 was higher than that among the 42 dogs with sCaPP ≤ 70 mg2/dL2. Dogs with sCaPP > 70 mg2/dL2 had a comparatively lower survival rate, and risk of death was 4.2 times as high as risk for dogs with sCaPP ≤ 70 mg2/dL2.
Conclusions and Clinical Relevance—For dogs with CKD, sCaPP > 70 mg2/dL2 appeared to be a negative prognostic indicator, which was not influenced by the concomitant serum concentrations of phosphorus and total or ionized calcium.
Each rabbit received IOX (64.7 mg/kg [0.1 mL/kg], IV), and blood samples were collected at predetermined times before and after administration. Plasma IOX concentration was determined by high-performance liquid chromatography. The pharmacokinetics of IOX was determined by a noncompartmental method. For each rabbit, plasma clearance of IOX was determined by dividing the total IOX dose administered by the area under the concentration-time curve indexed to the subject's body weight. The GFR estimated from the plasma IOX concentration at 6 sampling times (referent model) was compared with that estimated from the plasma IOX concentration at 5 (model A), 4 (model B), and 3 (models C, D, and E) sampling times (limited-sampling models).
Mean ± SD GFR was 4.41 ± 1.10 mL/min/kg for the referent model and did not differ significantly from the GFR estimated by any of the limited-sampling models. The GFR bias magnitude relative to the referent model was smallest for model D in which GFR was estimated from plasma IOX concentrations at 5, 15, and 90 minutes after IOX administration.
CONCLUSIONS AND CLINICAL RELEVANCE
Results suggested that plasma clearance of IOX was a safe, reliable, accurate, and clinically feasible method to estimate GFR in domestic rabbits. Further research is necessary to refine the method.