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Updated: Dec 10, 2025

Estimation of Urinary Nanocrystals in Humans using Calcium Fluorophore Labeling and Nanoparticle Tracking Analysis
Published on: February 9, 2021
Urinary Calcium for Tracking Bone Loss and Kidney Stone Risk in Space.
Measuring urinary calcium (Uca) in space is crucial for monitoring bone loss and kidney stone risk. Averaging multiple Uca measurements effectively reduces variability, allowing for accurate detection of changes during spaceflight.
Area of Science:
- Space medicine
- Biomedical engineering
- Renal physiology
Background:
- Urinary calcium (Uca) levels in spaceflight are indicators of bone demineralization and kidney stone risk.
- Portable monitoring devices are being developed for in-space physiological measurements.
- Assessing the reliability of Uca measurements is essential for their clinical application in astronauts.
Purpose of the Study:
- To evaluate the repeatability of urinary calcium measurements.
- To determine the number of measurements needed to detect significant changes in Uca levels during spaceflight.
- To assess the feasibility of using first void concentration as an alternative to 24-hour collections.
Main Methods:
- Six subjects collected 24-hour urine samples over 8 weeks, with oral calcium and vitamin D supplementation in the final 2 weeks.
- Urinary calcium concentration was analyzed using a calcein-based system.
- Reproducibility coefficients (RPC) were calculated using Bland-Altman analysis for both 24-hour mass and first void concentration.
Main Results:
- Oral supplementation did not significantly alter 24-hour urinary calcium mass.
- First void urinary calcium concentration showed a significant correlation with 24-hour urinary calcium mass.
- Reproducibility coefficients improved with averaged measurements, indicating reduced variability for both 24-hour mass and first void concentration.
Conclusions:
- Averaging multiple urinary calcium measurements effectively reduces variability, enabling the detection of clinically significant elevations.
- Tracking consecutive Uca measurements over time can monitor the efficacy of countermeasures against bone loss in space.
- First void urinary calcium concentration may serve as a viable alternative to cumbersome 24-hour urine collections for spaceflight monitoring.

