Thank you for your question. For diabetes, albuminuria as the urinary albumin-creatinine ratio (uACR) test has long been the recommended screening test based on clinical practice guidelines from the American Diabetes Association, National Kidney Foundation and Kidney Disease Improving Global Outcomes (references for the clinical practice guidelines can be found at
https://ecqi.healthit.gov/sites/default/files/ecqm/measures/CMS951v2.html). According to the measure steward, the National Kidney Foundation (NKF), urinary protein-creatinine ratio (uPCR) is often used interchangeably with uACR. Both predict outcomes similarly. Both tests may be performed at least initially to help distinguish non-albumin proteinuria (tubular or overflow/paraproteinuria). In addition, the guidelines for diabetes have also recently recommended a 30% reduction in albuminuria as a clinical target when the uACR is 300 mg/g or more for monitoring. Conversely, increases in albuminuria are important to detect of course.
Further, the albuminuria therapeutic target recommendation is based on multiple recent high-quality randomized controlled trials in CKD and type-2 diabetes. These trials include Angiotensin Receptor Blockers (IDNT and RENAAL), SGLT2 inhibitors (CREDENCE, DAPA-CKD and EMPA-KIDNEY), Non-steroidal MRA (FIDELIO, FIGARO, FIDELITY), and GLP-1 RA (FLOW). There are also many active clinical trials, currently enrolling participants, that include albuminuria as an outcome in the analysis for both type-1 and type-2 diabetes. Prediction models, such as the CKD heat map and other validated prediction models (kidney failure risk equation and PREVENT cardiovascular risk calculator) also use albuminuria rather than proteinuria.
The uACR is currently in the process of being standardized, whereas uPCR is not feasible to be standardized. In the future, there should be less bias for uACR across laboratory methods than uPCR.
NKF is currently convening a Measurement of urinary proteins conference to assess the use of uACR versus uPCR for clinical trials and clinical practice, particularly for diseases other than diabetes in which there are less data for albuminuria (e.g glomerular diseases and pediatric kidney diseases).