Urinary creatinine concentration and urine color as indicators of specimen validity test

Abstract In this study, the concentration of urinary creatinine (Cr) and urine color were analyzed, and a correlation obtained, to objectively verify normal urine samples prior to forensic drug testing. Cr was analyzed via a colorimetric method based on the Jaffé reaction using a Cobas C-311 analyzer (Roche SA, Basel, Switzerland; Hitachi, Tokyo, Japan). The Cr concentration for urine specimen validity testing was measured to screen urine samples submitted after dilution or upon the addition of a foreign substance that interferes with drug testing. Urine samples containing < 20 mg/dL of Cr were classified as abnormal. The Korea Standard Color Analysis program was used for urine color analysis and correlations with Cr concentration analyzed. The color and Cr concentration of 271 urine samples were analyzed according to age and sex. The mean ± standard deviation of Cr concentration in males and females was 136.4 ± 66.2 mg/dL and 109.5 ± 71.1 mg/dL, respectively, with a statistically insignificant difference ( p = 0.4554). Furthermore, the participants were categorized into young (19–34 years), middle-aged (35–49 years), and elderly (≥ 50 years) groups to compare Cr concentration; however, no significant difference was found ( p = 0.2143–0.983). Strong variable correlations were identified between Cr and the characteristics of urine color. Despite various factors such as water consumption, health problems, and vitamins, urine color was found applicable for urine specimen validity testing. Future plans include the development of a smartphone camera application for use in urine color analysis to identify abnormal urine samples.