Abstract: SA-PO109

The Ability of Serial Spot Urine Protein/Creatinine Ratios to Correctly Identify Proteinuria Trend in Lupus Nephritis Varies Greatly from Patient to Patient

Session Information

Category: Glomerular

  • 1005 Clinical Glomerular Disorders

Authors

  • Ayoub, Isabelle, The Ohio State Wexner Medical Center, Columbus, Ohio, United States
  • Shidham, Ganesh B., Ohio State University, Columbus, Alabama, United States
  • Birmingham, Daniel J., Ohio State University, Columbus, Alabama, United States
  • Rovin, Brad H., Ohio State University Wexner Medical Center, Columbus, Ohio, United States
  • Hebert, Lee A., Ohio State University Medical Center, Columbus, Ohio, United States
Background

In most clinical laboratories the vast majority of testing for proteinuria in adult patients is based on spot protein/creatinine ratio (PCR). This follows KDIGO recommendations. It is widely recognized that spot PCR is more variable than 24h PCR testing. This is assumed to be a random property of spot PCR. In research, spot PCR variability is mitigated when data sets are averaged. However, in individual patient management, spot PCR’s variability could confound management. Here we show for the first time that spot PCR in many patients are highly unreliable estimates of proteinuria trend.

Methods

We analyzed the variability of longitudinal testing of spot PCR and 24h PCR in 103patients with stage III or IV lupus nephritis (LN) participating in the ACCESS multicenter randomized trial. The gold standard estimate of proteinuria trend is that described by the line joining the serial 24h PCR values. To assess spot PCR reliability we compared in each patient the trend in serial spot PCR values to that of their 24h PCR trend line. Using semi-quantitative technique we stratified the patients according to whether the sequential spot PCR were deemed to be reliable, problematic or unreliable in identifying proteinuria trends based on the gold standard, the 24h PCR trend line.

Results

Of the 103 patients who had follow up testing of concurrent spot PCR and 24h PCR, 41% (42/103) had reliable, 24% ( 25/103) had problematic, and 35%(36/103) had unreliable spot PCR. No baseline predictors were significantly associated with any of the three categories. Patients with unreliable spot PCR were more likely to have unfavorable outcomes of their LN.

Conclusion

Clinical decision making in LN management should not be based on spot PCR testing. Instead, a reliable estimate of proteinuria magnitude can be obtained with the PCR of intended 24 hour urines that are at least 50% complete based on their creatinine content.

Funding

  • NIDDK Support