Smartphone-based colorimetric correction analysis system for long-term urine monitoring of chronic kidney disease

The chronic kidney disease (CKD) poses a serious threat to human health. Long-term monitoring of urine is important in the management of CKD. Currently, the accuracy and stability of smartphone-based colorimetric analysis of urine indicators are limited due to the impact of different image-taking conditions on captured digital images of urine test strips. Herein, an attachment-free colorimetric correction analysis system (CCAS for short), consisting of a self-designed urine test strip array and an Android application integrated with an image calibration algorithm, were proposed for quantitative analysis of nine urine indicators. With this system the impact of image-taking conditions on captured digital image were largely corrected, and thus the accuracy and stability for digital image colorimetric analysis of urine test strip were improved. The limits of detection of creatinine, nitrite, urinary calcium, microalbumin, bilirubin, protein, pH, haemoglobin, and glucose were 1.607 mmol/L, 1.232 μmol/L, 0.297 mmol/L, 11.116 mg/L, 1.155 μmol/L, 0.042 g/L, 0.044, 0.058 mg/L, and 0.122 mmol/L, respectively. The accuracy of CCAS was validated by analyzing artificial urine samples and 143 clinical urine samples. As an accurate, low-cost and reliable system, CCAS addresses specific needs for patients to monitor their urine whenever and wherever possible with only their own smartphone.