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Kidney Week

Abstract: PO1569

Urine NAG Is an Effective Clinical Parameter to Presume Disease Activity of Autosomal Dominant Polycystic Kidney Disease

Session Information

Category: Genetic Diseases of the Kidneys

  • 1001 Genetic Diseases of the Kidneys: Cystic

Authors

  • Kogure, Yuta, School of Medicine, Saitama Medical University, Kawagoe, Saitama, Japan
  • Takayanagi, Kaori, School of Medicine, Saitama Medical University, Kawagoe, Saitama, Japan
  • Aoyagi, Mai, School of Medicine, Saitama Medical University, Kawagoe, Saitama, Japan
  • Hatano, Minoru, School of Medicine, Saitama Medical University, Kawagoe, Saitama, Japan
  • Iwashita, Takatsugu, School of Medicine, Saitama Medical University, Kawagoe, Saitama, Japan
  • Ogawa, Tomonari, School of Medicine, Saitama Medical University, Kawagoe, Saitama, Japan
  • Hasegawa, Hajime, School of Medicine, Saitama Medical University, Kawagoe, Saitama, Japan
Background

Patients with ADPKD are mixed with those who progress to ESRD and those who maintains stably, and should be assessed separately from disease activity shown in rate of kidney volume progression (RKVP), disease progression shown in total kidney volume (TKV), and also renal function shown in eGFR.This is also crucial in considering indication of tolvaptan. However, the evaluation of RKVP requires multiple imaging studies, and problems with costs and complexities. Considering that ADPKD is a disorider primarily affecting tubulo-interstitium, we aimed to examine the clinical potential of urine NAG to evaluate RKVP by retrospective obseration.

Methods

Among ADPKD patients treated in our hospital between January 2010 and June 2019, 62 patients who met the conditions of no tolvaptan use, GFR≧30, duration of treatment in our hospital≧1 year, and multiple TKV measurement by CT scanning were included in the analysis.

Results

The mean age was 46.3 years, 62.9% men, the mean baseline eGFR was 60.1±18.5 ml/min/L, the median TKV was 1137 mL, and the median urine NAG index (NAG-to-Cr ratio) was 4.64 U/mg Cr.
In the reduced renal function group (30≤eGFR< 60 mL/min, n=32), we observed a correlation between NAG index and RKVP in single-regression analyses (R2 = 0.330, p = 0.003), but not with eGFR, TKV.
However, there was no significant correlations between all parameter and RKVP, including NAG index, in the normal renal function group (eGFR≥60 mL/min, n=30).
Multiple regression analysis showed that NAG index was a predictor of RKVP in the reduced renal function group (p = 0.005).
Based on the approximate equation in the single-regression analyses of NAG index and RKVP (RKVP=1.511 X NAG index-2.869), the 95% confidence interval for NAG index (5.98-9.40 U/mgCr) in the reduced renal function group, and the corresponding RKVP values (6.16-11.33%/year), reasonable cut-off value of NAG index to predict RKVP≥5% per year might be considered to be 6.0 U/mgCr.

Conclusion

In ADPKD patients with renal dysfunction (CKD stage≤3), it was considered that NAG index may be useful as a predictor of the disease activity shown by RKVP and, if it is 6.0 U/mgCr or greater, may be presumed to be associated with higher disease activity.