Repeated albuminuria measurements offer a far more accurate picture of the progression of diabetic chronic kidney disease than current practice which does not account for within-individual variability, Australian researchers say.
The Baker Heart and Diabetes Institute-led team compared four urine tests repeated within 28 days from 826 participants with type 2 diabetes (mean age 67, 65% male) in the PREDICT study cohort, finding that albuminuria levels in a repeated test could be as high or as low as four times the original result.
Results published in the American Journal of Kidney Diseases [link here] showed that based on a single collection increase from 2 to 5 mg/mmol, there was a 50% probability that urinary albumin-creatinine ratio had increased by at least 30%.
The probability rose to 97% when two collections were used at each time point.
The ranges of diagnostic uncertainty were 2.0-4.0 mg/mmol after an initial urinary albumin-creatinine ratio test, narrowing to 2.4-3.2 and 2.7-2.9 mg/mmol for the mean of two and three collections, respectively, the researchers noted.
“We know that for someone living with type 2 diabetes, that their urine albumin-creatinine ratio can vary on a day-to-day basis, reflecting fluctuations in blood pressure and behavioural factors including exercise and posture. However, many healthcare professionals may be surprised to see that it can vary by such a large extent,” said Dr Julian Sacre (PhD), a Clinical Diabetes and Epidemiology researcher.
“Although the method and timing of urine collections can be standardised, it is very difficult to control for all of the factors that underlie within-individual variability. Therefore, we would advocate for multiple urine collections on different days to get a complete picture of albuminuria.”