Impact of weight and creatinine adjustments on the accuracy of Cockcroft-gault equation in hematopoietic cell transplant patients.

BACKGROUND: Hematopoietic cell transplant (HCT) patients undergo pre- transplant renal function evaluation to confirm transplant eligibility and tailor pharmacotherapy. There is limited evidence regarding the most accurate method of estimating creatinine clearance (CrCl) within this patient population and no studies exist that evaluate the weight utilized within the Cockcroft-Gault (CG) equation in HCT patients. This study evaluates different weight and serum creatinine (SCr) adjustments utilized within the CG equation estimating for renal clearance in patients undergoing HCT. OBJECTIVE: This is a retrospective, single center analysis of adult HCT patients who underwent pre-transplant evaluation with a measured CrCl using a 24-h urine creatinine collection. The primary outcome was to evaluate the correlation of various weights used in estimation of CrCl compared to measured CrCl. Key secondary outcomes include evaluation of the impact of various weights on estimated CrCl in subpopulations, evaluation of adjusting SCr to pre-determined limits, and determination of an appropriate obesity threshold to utilize body weight adjustments. RESULTS: Seven-hundred and forty-two patients were included in the study. In the primary analysis, CG utilizing adjusted body weight (ADjBW0.4 ) had a greater correlation (r = .812) to measured CrCl when compared to total or ideal body weight (r = .801 and r = .790 respectively). The threshold of 120% of ideal body weight (IBW) produced less bias and greater accuracy in comparison to the threshold of 140% IBW. In patients 60 years or older, rounding low SCr values up .8 or 1 mg/dL resulted in decreased correlation and a greater mean difference in comparison to not rounding SCr. CONCLUSION: In HCT patients who are overweight or obese, ADjBW .4 is the most accurate weight for the CG equation. In HCT patients who have a total body weight < 120% IBW, total body weight is the most accurate weight to utilize. Rounding up low SCr to .8 or 1 mg/dL does not improve the accuracy or led to less bias of the CG equation.