Kidney Week

Abstract: SA-PO482

Random Daytime Spot Urine Correlates with Twenty-Four Hour Urine Osmolality in Patients with Autosomal Dominant Polycystic Kidney Disease

Session Information

• ADPKD: Clinical Studies
  October 27, 2018 | Location: Exhibit Hall, San Diego Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidney

• 1001 Genetic Diseases of the Kidney: Cystic

Authors

• Mannix, Carly, The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia

Carly Mannix,

• Wong, Annette, The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia

Annette Wong,

• Zhang, Jennifer, The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia

Jennifer Zhang,

• Lee, Vincent W.S., The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia

Vincent W.S. Lee,

• Harris, David C., The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia

David C. Harris,

• Sud, Kamal, The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia

Kamal Sud,

• Rangan, Gopi, The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia

Gopi Rangan,

Group or Team Name

• PREVENT-ADPKD

Background

Urine osmolality (UOsm) is a surrogate measure of hydration and dietary solute intake, regulated by levels of circulating arginine vasopressin (AVP). Monitoring UOsm may be useful to gauge adherence to fluid and diet prescriptions in autosomal dominant polycystic kidney disease (ADPKD). Traditionally, UOsm has been determined by 24hr urine collection but patients find this method cumbersome, and hence we investigated if spot urine could serve as an alternative method. The aim of this study was to determine the relationship between random daytime spot UOsm and 24hr UOsm in patients with ADPKD.

Methods

Random spot urine was collected prospectively from ADPKD patients (18-65 years, eGFR≥30 mL/min/1.73m²) during the Screening Visit of the PREVENT-ADPKD study (a randomised controlled trial investigating the efficacy of prescribed fluid intake on kidney cyst growth). Urine specific gravity (USG) and serum copeptin (a biomarker of AVP release) were also analysed at the study visit, and patients then performed two 24hr urine collections over the subsequent 12 weeks.

Results

Seventy-nine participants were included (age:43±11 ys; 54% male). The mean spot UOsm was 491±196 mOsmol/L and correlated moderately with the mean 24hr UOsm (424±173 mOsmol/L; r=0.56; P<0.001). In contrast, the association between spot UOsm to urine creatinine ratio and the mean 24hr UOsm was weak (r=0.16, P=0.03). As expected, spot UOsm predicted the USG (P<0.001), and the latter was also positively correlated with the mean 24hr UOsm (r=049, P<0.001). Spot UOsm had a weak association with serum copeptin (median 4.2, range 0.9-28.1 pmol/L; r=0.26; P<0.001).

Conclusion

These data suggest that spot urine collected randomly during the day (either at a clinic visit for measurement of UOsm or by patient self-monitoring for USG) may be an alternative method to estimate 24hr UOsm in patients with ADPKD. Further prospective studies and the outcome of the PREVENT-ADPKD trial are required to validate these findings.

Funding

• Commercial Support –