Assessing dehydration status in dengue patients using urine colourimetry and mobile phone technology

Abstract

Background: Dengue is a systemic and dynamic disease with symptoms ranging from undifferentiated fever to dengue shock syndrome. Assessment of patients' severity of dehydration is integral to appropriate care and management. Urine colour has been shown to have a high correlation with overall assessment of hydration status. This study tests the feasibility of measuring dehydration severity in dengue fever patients by comparing urine colour captured by mobile phone cameras to established laboratory parameters.

Methodology/principal findings: Photos of urine samples were taken in a customized photo booth, then processed using Adobe Photoshop to index urine colour into the red, green, and blue (RGB) colour space and assigned a unique RGB value. The RGB values were then correlated with patients' clinical and laboratory hydration indices using Pearson's correlation and multiple linear regression. There were strong correlations between urine osmolality and the RGB of urine colour, with r = -0.701 (red), r = -0.741 (green), and r = -0.761 (blue) (all p-value <0.05). There were strong correlations between urine specific gravity and the RGB of urine colour, with r = -0.759 (red), r = -0.785 (green), and r = -0.820 (blue) (all p-value <0.05). The blue component had the highest correlations with urine specific gravity and urine osmolality. There were moderate correlations between RGB components and serum urea, at r = -0.338 (red), -0.329 (green), -0.360 (blue). In terms of urine biochemical parameters linked to dehydration, multiple linear regression studies showed that the green colourimetry code was predictive of urine osmolality (β coefficient -0.082, p-value <0.001) while the blue colourimetry code was predictive of urine specific gravity (β coefficient -2,946.255, p-value 0.007).

Conclusions/significance: Urine colourimetry using mobile phones was highly correlated with the hydration status of dengue patients, making it a potentially useful hydration status tool.

Fig 1. Photo booth setup to capture urine colour.

The schematic of the photo booth along with placements of urine bottle and light source.

Fig 2. Association of the blue component of RGB urine colour value with dehydration assessment by clinician, dengue severity, oral fluid intake and hospital admission.

Hydration category was based on the blue component of RGB urine value according to the Body Hydration Tracker system proposed by Jeanette et al. (2015); a value <40 indicates serious dehydration, 40 to 100 indicates significant dehydration, 100 to 170 indicates minimal dehydration and >170 indicates well hydration [18]. * denotes significant p-value calculated using Mantel-Haenszel statistics.