Day-to-Day Variability in Spot Urine Albumin-Creatinine Ratio

作者：Naresh Chetana N; Hayen Andrew; Weening Alexander; Craig Jonathan C; Chadban Steven J^*

来源：American Journal of Kidney Diseases, 2013, 62(6): 1095-1101.

DOI：10.1053/j.ajkd.2013.06.016

• Albuminuria
• albumin-creatinine ratio
• proteinuria
• chronic kidney disease.

Background: Accurate quantification of albuminuria is important in the diagnosis and management of chronic kidney disease. The reference test, a timed urinary albumin excretion, is cumbersome and prone to collection errors. Spot urine albumin-creatinine ratio (ACR) is convenient and commonly used, but random day-to-day variability in ACR measurements has not been assessed. %26lt;br%26gt;Study Design: Prospective cohort study of day-to-day variability in spot urine ACR measurements. %26lt;br%26gt;Setting %26 Participants: Clinically stable outpatients (N = 157) attending a university hospital clinic in Australia between July 2007 and April 2010. %26lt;br%26gt;Outcomes: Spot urine ACR variability was assessed and repeatability limits were determined using fractional polynomials. %26lt;br%26gt;Measurements: ACRs were measured from spot urine samples collected at 9:00 AM on consecutive days and 24-hour urine albuminuria was measured concurrently. %26lt;br%26gt;Results: Paired ACRs were obtained from 157 patients (median age, 56 years; 60% men; median daily albumin excretion, 226 [range, 2.5-14,000] mg/d). Day-to-day variability was substantial and increased in absolute terms, but decreased in relative terms, with increasing baseline ACR. For patients with normoalbuminuria (ACR %26lt; 3 mg/mmol [%26lt;27 mg/g]), a change greater than +/-467% (0-17 mg/mmol [0-150 mg/g]) is required to indicate a significant change in albuminuria status with 95% certainty; for those with microalbuminuria (ACR of 3-30 mg/mmol [27-265 mg/g]), a change of +/-170% (0-27 mg/mmol [0-239 mg/g]) is required; for those with macroalbuminuria (ACR %26gt; 30 mg/mmol [%26gt;265 mg/g]), a change of +/-83% (5-55 mg/mmol [44-486 mg/g]) is required; and for those with nephrotic-range proteinuria (ACR %26gt; 300 mg/mmol [%26gt;2,652 mg/g]), a change of +/-48% (158-443 mg/mmol [1,397-3,916 mg/g]) is needed to represent a significant change. %26lt;br%26gt;Limitations: These study results need to be replicated in other ethnic groups. %26lt;br%26gt;Conclusions: Changes in chronic kidney disease status attributed to therapy or disease progression, when based solely on a change in ACR, may be incorrect unless the potential for day-to-day biological variation has been considered. Only relatively large changes are likely to indicate a change in disease status.

• 出版日期2013-12