Pretransplant Hypoalbuminemia As A Predictor of Medical Arterial Calcification During Waiting List Pre‐Kidney Transplant Period: A Propensity Score Weighting Analysis

Abstract

IntroductionMedial arterial calcification (MAC) is common in advanced chronic kidney disease and end‐stage renal disease. Whether serum albumin as a surrogate marker of inadequate dialysis is associated with MAC is unknown.MethodsSince breast arterial calcification is exclusively medial, mammogram was used to identify MAC. Renal transplant recipients (RTR) with MG during pretransplant period was divided into 2 groups: pretransplant normoalbuminemia and hypoalbuminemia (serum albumin <4 g/dL). Baseline characteristics including potential confounders were balanced by propensity score weighting(PSW). Association between serum albumin status and MAC during pretransplant period is examined by multiple logistic regression.ResultsOf 51 RTR, mean age±SD was 57±10.5 years old and the majority were white 28 (54%) followed by African American 18 (35%) and others 5 (9%) patients. Five patients never been on dialysis and 34 patients had dialysis (29 with hemodialysis and 5 with peritoneal dialysis) with a median time of dialysis prior to kidney transplantation was 3.79 years (0.72 to 20.38 years). Among 34 patients with hypoalbuminemia, 16 patients had MAC; whereas only 4 out of 17 patients in normoalbuminemia had MAC (47.06% vs. 23.53%, p 0.135). Mean serum albumin were 3.3±0.6 and 4.2±0.2 g/dL in hypoalbuminemic and normoalbuminemic groups, respectively (p <0.001). Baseline characteristics and potential confounders including age, race, cause of kidney diseases, dialysis modalities, pretransplant obesity status, diabetes, corrected calcium, and phosphorus were balanced by using PSW with generalized boosted modeling (Figure 1 and 2). Hypoalbuminemic group had 3.09 times higher the odds of having MAC compared to normoalbuminemic group, but the association was not significant (OR 3.09; 95%CI 0.62 to 15.41). By using multiple logistic regression with adjustment for co‐variated used in the PSW, the magnitude of the association became significant with a 75.55 times greater the odds of MAC in hypoalbuminemic group compared to normoalbuminemic group (OR 75.55; 95%CI 1.42 to 4013.69).ConclusionsNot only being one of the surrogate markers of malnutrition and inadequate dialysis, hypoalbuminemia is also associated with MAC in well‐matched study population using PSW. Since MAC is associated with higher mortality in RTR, hypoalbuminemia during pretransplantation should be corrected to improve posttransplant outcomes.Love plot estimating propensity score weights using generalized boosted modeling with balancing covariatesFigure 1Histogram estimating propensity score weights using generalized boosted modeling with balancing covariatesFigure 2