Analysis of the Distribution of Urine Color and Its Relationship With Urine Dry Chemical Parameters Among College Students in Beijing, China – A Cross-Sectional Study

Abstract

Objectives: The objective of this study was to provide a new classification method by analyzing the relationship between urine color (Ucol) distribution and urine dry chemical parameters based on image digital processing. Furthermore, this study aimed to assess the reliability of Ucol to evaluate the states of body hydration and health.Methods: A cross-sectional study among 525 college students, aged 17–23 years old, of which 59 were men and 466 were women, was conducted. Urine samples were obtained during physical examinations and 524 of them were considered valid, including 87 normal samples and 437 abnormal dry chemistry parameters samples. The urinalysis included both micro- and macro-levels, in which the CIE L*a*b* values and routine urine chemical examination were performed through digital imaging colorimetry and a urine chemical analyzer, respectively.Results: The results showed that L* (53.49 vs. 56.69) in the abnormal urine dry chemistry group was lower than the normal group, while b* (37.39 vs. 33.80) was greater. Urine color can be initially classified based on shade by grouping b*. Abnormal urine dry chemical parameter samples were distributed more in the dark-colored group. Urine dry chemical parameters were closely related to Ucol. Urine specific gravity (USG), protein, urobilinogen, bilirubin, occult blood, ketone body, pH, and the number of abnormal dry chemical parameters were all correlated with Ucol CIE L*a*b*; according to a stepwise regression analysis, it was determined that more than 50% of the variation in the three-color space values came from the urine dry chemical parameters, and the b* value was most affected by USG (standardized coefficient β = 0.734, p < 0.05). Based on a receiver operating characteristic curve (ROC) analysis, Ucol ≥ 4 provided moderate sensitivity and good specificity (AUC = 0.892) for the detection of USG ≥ 1.020.Conclusions: Our findings on the Ucol analysis showed that grouping Ucol based on b* value is an objective, simple, and practical method. At the same time, the results suggested that digital imaging colorimetry for Ucol quantification is a potential method for evaluating body hydration and, potentially, health.

Validation of urine colour L*a*b* for assessing hydration amongst athletes

“…This suggests that the b* value had the highest validity compared with L* and a* values for assessing hydration in athletes. Differences in correlation coefficients in similar studies ( 11 , 13 , 14 ) might be related to factors such as detection instruments, cuvette light path, sediment deposits in urine samples, sample size and subjects.…”

“…This suggests that the b * value had the highest validity compared with L * and a * values for assessing hydration in athletes. Differences in correlation coefficients in similar studies (11,13,14) might be related to factors such as detection instruments, cuvette light path, sediment deposits in urine samples, sample size and subjects. The ROC curve further proved that the urine colour b * value could be used as an effective indicator for assessing different stages of hydration, and L * and a * values were not feasible to distinguish the hydration amongst athletes (Figures 4, 5 and Tables 2, 3).…”

“…The results showed that there was a significant linear relationship between urine colour b* value and urine osmolarity ( r = 0.708, p < 0.05), which coincide with the results of this study; there was a moderate negative correlation between urine colour L* value and urine osmolarity ( r = −0.567, p < 0.05), which was similar to the results of this study; there was also a low negative correlation between urine colour a* value and urine osmolarity ( r = −0.375, p < 0.05), which was slightly different from the results of this study. Liu et al ( 14 ) conducted a cross-sectional study on a total of 525 college students aged 17–23 (59 males, 466 females). They collected a total of 524 urine samples at different time points, imaging equipment was used to obtain urine images CIE L*a*b* and a Deere H-800 urine analyser was used to detect urine specific gravity.…”

“…In recent years, researchers have tried to quantitatively analyse urine colour L * a * b * through the use of instruments (11)(12)(13)(14). Renal function varies amongst populations, hence, the validity of urine colour L * a * b * parameters for assessing hydration of athletes is unclear.…”

Urine Analysis has a Very Broad Prospect in the Future

“…Some experiments have proved that the health of athletes can be monitored through urine observation and analysis, so as to protect the health of athletes and improve their physical fitness (Pero et al, 2020), which also indicates whether ordinary healthy people can also perform health self-examination through urine. Accessibility makes it easier for people to monitor their physical health (Liu et al, 2020;Liu et al, 2021). Today, with the continuous development of medical inspection technology, these are all possible ideas.…”