Normoalbuminuria-is it normal? The association of urinary albumin within the 'normoalbuminuric' range with adverse cardiovascular and mortality outcomes: A systematic review and meta-analysis

AIM

To assess the association between urinary albumin-to-creatinine ratio (UACR) categories within the normal range with mortality and adverse cardiovascular outcomes.

MATERIALS AND METHODS

PubMed and Embase were systematically searched for real-world evidence studies. Studies were manually evaluated according to predefined eligibility criteria. We included prospective and retrospective cohort studies of the association between UACR categories <30 mg/g and cardiovascular outcomes or mortality. Published information regarding study design, participants, UACR categorization, statistical methods, and results was manually collected. Two UACR categorization approaches were defined: a two-category (UACR <10 mg/g vs. 10-30 mg/g) and a three-category division (UACR <5 mg/g vs. 5-10 and 10-30 mg/g). A random effects meta-analysis was performed on studies eligible for the meta-analysis.

RESULTS

In total, 22 manuscripts were identified for the systematic review, 15 of which were eligible for the meta-analysis. The results suggest an association between elevated UACR within the normal to mildly increased range and higher risks of all-cause mortality, cardiovascular death, and coronary heart disease, particularly in the range of 10-30 mg/g. Compared with UACR <10 mg/g, the hazard ratio [HR (95% confidence interval, CI)] for UACR between 10 and 30 mg/g was 1.41 (1.15, 1.74) for all-cause mortality and 1.56 (1.23, 1.98) for coronary heart disease. Compared with UACR <5 mg/g, the risk of cardiovascular mortality for UACR between 10 and 30 mg/g was more than twofold [HR (95% CI): 2.12 (1.61, 2.80)]. Intermediate UACR (5-10 mg/g) was also associated with a higher risk of all-cause mortality [HR (95% CI): 1.14 (1.05, 1.24)] and cardiovascular mortality [HR (95% CI): 1.50 (1.14, 1.99)].

CONCLUSIONS

We propose considering higher UACR within the normoalbuminuric range as a prognostic factor for cardiovascular morbidity and mortality. Our findings underscore the clinical significance of even mild increases in albuminuria.

Low grade albuminuria as a risk factor for subtypes of stroke - the HUNT Study in Norway

BACKGROUND AND PURPOSE

Albuminuria is a marker for endothelial dysfunction and knowledge on its association with stroke and stroke subtypes are limited.

METHODS

Corresponding data from 7261 participants of the population-based HUNT2 study (1995-1997) was linked with hospital records, identified all patients registered and diagnosed with a first-time stroke. Each diagnosis was validated by reviewal of the medical record appertaining to the individual. We then applied Cox proportional hazard models to estimate the hazard ratios (HRs) for the association between albuminuria (measured as albumin-to-creatinine-ratio, ACR) and diagnosis of stroke and stroke subtypes.

RESULTS

703 (9.7%) participants developed a first ischemic stroke during a median follow-up of 15 years. Higher albuminuria was associated with a higher rate for ischemic stroke and the risk rose steadily with increasing ACR (15% increment per unit increase in ACR concentration in mg/mmol). In the fully adjusted model, the HR for all ischemic strokes was 1.56 (95% CI 1.24-1.95) for those with an ACR ≥3 mg/mmol compared to participants with an ACR < 1 mg/mmol. Overall, increasing ACR was associated with a higher risk of all ischemic stroke subtypes. This was seen to be strongest for lacunar stroke (HR 1.75, CI 1.12-2.72, p = 0.019), and also for stroke of undetermined etiology (HR 1.53, CI 1.11-2.11, p = 0.009) and those caused by atherosclerosis in the large arteries (HR 1.51, CI 0.78-2.94, p = 0.186) than for cardio-embolic stroke (HR 1.22, CI 0.64-2.3, p = 0.518).

CONCLUSIONS

Albuminuria is an important risk factor, potentially already at low grade, for ischemic stroke especially for lacunar subtype. Measuring albuminuria is both cheap and readily available. This offers the opportunity to evaluate the risk for endothelial dysfunction and thus the subsequent risk for stroke and cerebral small vessel disease.