Urine Concentration App Outperforms Common Clinical Hydration Measures

An innovative mobile phone application determined hydration status better than thirst, urine color scales and dipstick tests in a pilot study. 

Columbus, OH — September 2018

A point-of-care tool for clinicians or patients to quickly and accurately measure urine concentration may offer a practical way to monitor hydration status and prevent complications, particularly for nephrology patients. Now, a team at Nationwide Children’s Hospital has developed an application for mobile phones that performs better than many current clinical urine concentration tests, including specific gravity by dipstick, urine color scale and patient-reported thirst assessments.

Urine concentration may be a key health indicator in many pediatric patients with kidney stones, urinary tract infections, autosomal dominant polycystic kidney disease (ADPKD) and other conditions. For these patients, maintaining proper hydration may help reduce the likelihood of complications of their disease.

“There is data supporting the use of apps to improve adherence in diabetes care, and we wanted to start extending that into other areas of practice,” says Laura Walawender, MD, pediatrics chief resident at Nationwide Children’s and a clinician-researcher collaborating with the hospital Nephrology team. She is lead author on the study’s publication, which appeared this summer in Frontiers in Pediatrics.

“The idea was to come up with a better point-of-care tool to assess hydration status, with the ultimate goal of creating something patients could use outside of the doctor’s office to follow their health indicators and manage their care between visits,” Dr. Walawender says.

A unique partnership between a team of nephrologists and technology development specialists at Nationwide Children’s resulted in a pilot iPhone app. The team enrolled 21 children, aged 12 to 17, to help test the app’s ability to detect urine concentration. The patients were being followed for blood pressure or hypertension issues, kidney stones and hypercalciuria, hematuria, polycystic kidney disease and other reasons.

Twenty-five urine samples were tested and 15 were randomly selected to check test-retest reliability of the app. Each patient was asked to rate their thirst on a visual-analog scale, and every sample was tested with a specific gravity refractometer, a specific gravity automated dipstick analysis by Clinitek, and a urine color scale scored by the patient as well as four separate researchers. Urine osmolality was obtained to be the gold standard for comparison.

“One thing we’ve learned from other projects that require photo analysis is that the images are always non-standard — they’re taken inside, outside, in the sun or under fluorescent light, and these are all things you have to compensate for when analyzing the photo for something like urine specific density,” says Jeremy Patterson, lead developer in the department of User Experience Technology Research and Development in The Research Institute at Nationwide Children’s.

He programmed the app based on the premise that urine osmolality would be inversely proportional to light penetrance. Collaborating with User Experience Specialist Robert Strouse, the two conceived of a light-tight device that holds a standard urine sample container, similar to light boxes used for product photo shoots. Once created by a 3-D printer, the device positions the urine specimen and iPhone camera at a fixed length and angle to one another, using the phone’s LED light to capture multiple photos under consistent conditions. The app then runs a regression analysis and reports the most likely results. 

The app’s light penetrance measurement of urine concentration performed as well as or significantly better than all other measures tested, with the exception of the specific gravity test run by refractometer, which would not likely be a practical option for at-home testing. Interestingly, thirst perception was not well correlated with actual urine osmolality, suggesting it is not a helpful indicator of hydration status.

Overall, the multidisciplinary team believes the app is a promising and practical tool for assessing hydration both in the clinic or at home.

“Mobile applications are probably the future of patient self-management and even patient-physician communication between visits,” says Dr. Walawender. “Hopefully tools like ours become a beneficial part of that new wave of care.”

Walawender L, Patterson J, Strouse R, Ketz J, Saxena V, Alexy E, Schwaderer A. Mobile Technology Application for Improved Urine Concentration Measurement Pilot Study. Frontiers in Pediatrics. 2018 Jun 6; 6:160.