Microalbuminuria After Kidney Transplantation Predicts Cardiovascular Morbidity

Abstract

Background: Microalbuminuria is a well-characterized marker of kidney malfunction, both in diabetic and non-diabetic populations, and is used as a prognostic marker for cardiovascular morbidity and mortality. A few studies implied that it has the same value in kidney transplanted patients, but the information relies on spot or dipstick urine protein evaluations, rather than the gold standard of timed urine collection. Methods: We revisited a cohort of 286 kidney transplanted patients, several years after completing a meticulously timed urine collection and assessed the prevalence of major cardiovascular adverse events (MACE) in relation to albuminuria. Results: During a median follow up of 8.3 years (IQR 6.4-9.1) 144 outcome events occurred in 101 patients. By Kaplan-Meier analysis microalbuminuria was associated with increased rate of CV outcome or death (p = 0.03), and this was still significant after stratification according to propensity score quartiles (p = 0.048). Time dependent Cox proportional hazard analysis showed independent association between microalbuminuria and CV outcomes 2 years following microalbuminuria detection (HR 1.83, 95% CI 1.07-2.96). Conclusions: Two years after documenting microalbuminuria in kidney transplanted patients, their CVD risk was increased. There is need for primary prevention strategies in this population and future studies should address the topic.

Keywords: albuminuria; cardiovascular morbidity; kidney transplantation; proteinuria; urine collection.

Figure 1

Consort diagram describing addition and reduction of patient to create the analyzed cohort.

Figure 2

Kaplan-Meier analysis showing rates of CV outcome or death in relation to microalbuminuria. X axis shows days since urine collection, Y axis shows cumulative survival. Blue curve—patients without microalbuminuria, red curve—patients with microalbuminuria.

Figure 3

Subgroup analysis of CVD risk according to presence of microalbuminuria. Each couple presents a certain subpopulation according to a certain risk factor. Each column illustrates the relation between Hazard Ratio (HR) (Y axis) and presence of a risk factor (X axis). Black line across each column represents Confidence Interval for HR. None of the interactions were significant with p = 0.078, p = 0.295, p = 0.376, p = 0.803, p = 0.451, p = 0.366, and 0.245 for interaction with gender, Diabetes Mellitus (DM), history of heart disease, hypertension, time from transplantation, living donor, respectively, and median age (56 years). DM, Diabetes Mellitus; TFT, time from transplantation, >/< 1 y, more or less than a year; H IHD, history of ischemic heart disease. Older/younger—above and below median age (56.6 years).