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

• Main Authors: Chew, Natalie, Azhar, Abdul Muhaimin Noor, Bustam, Aida, Azanan, Mohamad Shafiq, Wang, Crystal C., Lum, Lucy Chai See
• Format: Article
• Published: Public Library of Science 2020
• Subjects: RA Public aspects of medicine
• Online Access: http://eprints.um.edu.my/36425/
• Institution: Universiti Malaya

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 (beta coefficient -0.082, p-value <0.001) while the blue colourimetry code was predictive of urine specific gravity (beta 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. Author summary The vast majority of symptomatic dengue infections will result in an uncomplicated disease course. A small proportion will develop severe dengue late in the course of disease, on about day 4 or 5 of illness. In the absence of early prognostic markers to triage dengue patients for early supportive intervention, all suspected dengue cases are followed up for daily assessment, which includes an assessment of dehydration. While the clinical assessment of dehydration is subjective, the passing of dark-coloured urine is an accepted indicator of dehydration. However, visual assessment of urine colour is limited by the varied perception of colour and ambient lighting. An objective method to assess urine colour is to encode it in the RGB model. We used a mobile phone to capture an image of urine samples under standardised conditions and computed the RGB value of each image. Our study demonstrated that RGB urine colourimetry using mobile phones is highly correlated with the hydration status of dengue patients, making it a hydration status tool of great potential.