Spot urine protein to creatinine ratio

In a recent article in Pediatric Nephrology, EM Yang and colleagues (Pediatr Nephrol 2017: doi: 10.1007/s00467-016-3587-6 ) published a retrospective cross-sectional study involving a cohort of 442 children with an mean estimated glomerular filtration rate of >60 mL/min/1.73 m². The authors measured 24-h urine protein excretion (24-h UProt) alongside the morning spot urine protein to creatinine ratio (Prot/Cr) in this group of patients. While the Prot/Cr may be the only feasible way to routinely estimate the daily protein excretion of a young child, inter-individual variability in childrens' urinary creatinine excretion (UCr) may heavily influence the result. The authors sought to determine which equation was the most accurate in predicting UCr. Not only did they discover that the adult Cockcroft-Gault equation worked best, they also found that multiplying the Prot/Cr by the estimated UCr significantly improved the accuracy of the 24-h UProt estimate. In this editorial we discuss both the strengths and limitations of the study by EM Yang and colleagues. We also highlight the importance of adhering to internationally agreed upon reporting guidelines such as the STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) statement.