USA: A study of a large cohort of patients with common forms of CKD (chronic kidney disease) found an independent association of the urine-to-plasma ratio of urea ([U/P]urea) with disease progression and incident kidney failure. The findings appeared in the American Journal of Kidney Diseases on November 07, 2022.
An association of urinary concentrating capacity with CKD progression, independently of glomerular filtration rate (GFR), supports the notion that a more comprehensive assessment of kidney function than is typically performed in clinical practice today, might improve risk prediction. The GFR, despite being the primary indicator of kidney function, does not fully capture the kidneys' state of health, even with the addition of albuminuria. In a large cohort of patients with common forms of CKD, researchers found that a lower [U/P]urea was associated with more rapid eGFR decline and the development of kidney failure independently of other major risk factors for CKD progression.

The key findings of the study were as follows:
Median (interquartile range) [U/P]urea was 14.8. Compared to participants in the highest [U/P]urea quintile, those in the lowest quintile had a greater eGFR decline by 1.06 ml/min per 1.73m 2 per year over 7.0 years of follow-up.
Each 1 standard deviation decrease in natural log-transformed [U/P]urea was independently associated with CKD progression (HR 1.22) and incident ESKD (HR 1.22). Associations differed by baseline eGFR.
Among those with an eGFR ≥30 ml/min per 1.73m 2 , each 1 standard deviation decrease in log-[U/P]urea was independently associated with CKD progression (HR 1.30), but this was not significant among those with eGFR <30 ml/min per 1.73m 2 (HR 1.00).
Urea distinguishes itself from many other proposed biomarkers of tubular function by its central role in kidney physiology. Moreover, it is easily measured at a low cost in most clinical laboratories using standardized assays. Thus, [U/P]urea could represent an accessible marker of CKD progression, not only in ADPKD, but in forms of CKD with high prevalence.
Reference:
Jing Liu, Lise Bankir, Ashish Verma, Sushrut S. Waikar, Ragnar Palsson, Published:November 07, 2022DOI: https://doi.org/10.1053/j.ajkd.2022.09.010