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Abstract: SA-PO0067

Urine Protein-to-Creatinine Ratio in the Nephrotic Range During AKI Enables Identification of Previously Unknown Glomerular Pathology

Session Information

Category: Acute Kidney Injury

  • 102 AKI: Clinical, Outcomes, and Trials

Authors

  • Punukollu, Pooja A., UQ-Ochsner Clinical School, New Orleans, Louisiana, United States
  • Chachad, Ravi, UQ-Ochsner Clinical School, New Orleans, Louisiana, United States
  • Tupil, Ajay, UQ-Ochsner Clinical School, New Orleans, Louisiana, United States
  • Velez, Juan Carlos Q., Ochsner Health, New Orleans, Louisiana, United States
Background

Assessment of urine protein-to-creatinine ratio (UPCR) is deemed flawed in the context of acute kidney injury (AKI); therefore, it is often discouraged to order it. A nonsteady state of urine creatinine excretion and concentration artifact from oliguria are some of the concerns in the interpretation of UPCR during AKI. Our aim was to examine the frequency in which an inpatient high UPCR resulted in new diagnosis of a glomerular disease.

Methods

We utilized a prospective observational cohort of patients with AKI seen for inpatient nephrology consultation and who completed urinary sediment microscopy. We identified those with a UPCR indicative of nephrotic range proteinuria (UPCR > 3.0 g/g). To assess the validity of the inpatient nephrotic UPCR value, we assessed its correlation with pre-hospitalization (known nephrotic) and post-AKI (1-6 months before/after, validating) UPCR values, and examined the rate of new diagnosis of glomerular disease.

Results

Among 930 patients with AKI, 112 (12%) had a UPCR > 3.0 g/g [mean age 53, 42% women, median UPCR 5.9 g/g (3.1-41.5)]. Both pre-hospitalization and follow-up UPCR were missing in 18 (16%). Among those with de novo nephrotic UPCR and available follow-up UPCR (n=68), inpatient nephrotic UPCR significantly correlated with follow-up UPCR (r=0.329, p=0.006). In 32 of them (47%), a new biopsy-proven diagnosis of a glomerular disease was made. Concomitant hematuria was detected in 27 of those 32 cases (84%). Treatment-induced resolution of proteinuria could have led to underestimation of the validity of inpatient nephrotic UPCR detection. Five (7%) cases were characterized by absence of nephrotic UPCR upon immediate repeat, i.e., deemed false positives. Among those with available pre-hospitalization UPCR value (n=26), inpatient nephrotic UPCR strongly correlated with pre-hospitalization UPCR (r=0.684, p<0.001).

Conclusion

Identification of nephrotic UPCR during the evaluation of an AKI frequently led to the diagnosis of a previously unknown glomerular disease or aligned with a known baseline value. False positive rate is low. Therefore, UPCR should be ordered as part of diagnostic work-up for AKI and nephrotic UPCR values should not be disregarded, especially when accompanied by hematuria.

Digital Object Identifier (DOI)