We evaluated the effectiveness of the "Picolumi ucOC" kit for measuring the serum level of ucOC. When used with an autoanalyzer, the kit achieved highly sensitive and rapid measurement over a range of 0.39 to 50 ng/mL. Assessment of reproducibility testing showed good results, since the coefficient of variation was <or= 10%, the recovery rate for spiked samples was 93 - 106%, and there was no influence of interfering substances at normal levels. Among healthy individuals, serum ucOC levels were shown to be high in teenagers, who have very active bone metabolism, and in women aged 45 years or older, whose bone metabolism is influenced by menopause.