Abnormal urine protein dipstick results rarely followed up, study finds
An analysis of more than one million people tested across 33 U.S. health systems found that 13% had abnormal protein levels, but only 6.7% of those with abnormal results had further testing for albuminuria within a year.
Very few patients with abnormal urine protein dipstick results had follow-up albuminuria testing as recommended by clinical guidelines, a study of more than one million health records found.
Researchers used anonymous electronic health record data from a large database to identify adults who had a doctor's visit in 2021 that included a blood test to check kidney function and a urine dipstick to test for proteinuria. Patients were excluded if they had conditions that may cause proteinuria or known albuminuria determined by albumin-creatinine ratio (ACR) or equivalent protein-creatinine ratio (PCR) or had prior ACR or PCR testing within six months before the index date.
The primary outcome was subsequent quantitative albuminuria testing with ACR or PCR, estimated over one year. The researchers also estimated the proportion of individuals with an abnormal result on a protein dipstick test who were subsequently confirmed to have albuminuria, defined as an ACR or equivalent PCR value of 30 mg/g or higher. Additional analyses were stratified by dipstick proteinuria severity and presence of diabetes, hypertension, and chronic kidney disease (CKD). The brief research report was published Oct. 1 by Annals of Internal Medicine.
Of more than one million people tested across 33 U.S. health systems, 138,306 (13%) had abnormal protein levels. Within one year, only 6.7% of those with abnormal results had further testing for albuminuria, compared to 4.0% of those with normal results. Follow-up testing rates were slightly higher when the initial abnormal test results were higher: 6.3%, 7.3%, and 8.0% for 1+, 2+, and 3+ or greater protein, respectively (P<0.001 for trend).
Of those who had follow-up tests, 43.3% had confirmed albuminuria. Most of the follow-up albuminuria testing was done with ACR (86%). Among the 7,967 participants with initial abnormal results on a dipstick protein test who had follow-up albuminuria quantification testing, the proportion who had a positive result confirming albuminuria increased with higher baseline protein levels, from 36.3% (95% CI, 35.0% to 37.6%) for 1+ protein to 53.0% (95% CI, 50.9% to 55.1%) for 2+ protein and 64.9% (95% CI, 61.4% to 68.5%) for 3+ or greater protein. The percentages with confirmatory albuminuria were similar for participants with and without diabetes, and results were consistent when two results were used to confirm albuminuria.
According to the study authors, these findings show a crucial opportunity to better identify patients with kidney disease through follow-up ACR testing after abnormal protein dipstick results, allowing patients to reduce their heart and kidney risk with appropriate therapies.
“There is a crucial need for follow-up with ACR testing, which offers greater accuracy and is essential for determining whether to initiate cardiorenal protective therapies,” the authors wrote. “Improved education on the necessity of follow-up albuminuria quantification and the implementation of guideline-recommended ACR testing would benefit many patients through earlier detection and treatment of albuminuric CKD.”
A Pearls from I.M Peers in the January I.M. Matters from ACP discussed “Urinalysis as a ‘Liquid Biopsy of the Kidney.’”