Liquid-chromatographic determination of total hydroxyproline in urine

In this method for quantifying 4-hydroxyproline in human urine, 50 microL of urine is hydrolyzed, derivatized with phenylisothiocyanate (PITC), and then quantified by reversed-phase HPLC with ultraviolet detection. The detection limit in urine is 373 pg of hydroxyproline per 50-microL injection. The total CVs for high- and low-concentration pools are 5.3% and 3.9%, respectively (10 runs in 10 days). The standard curve of the assay is linear over a range of 0 to 22 nmol per injection. We estimated the normal range for hydroxyproline excretion in men on an unrestricted diet to be 123-308 mumol/24 h. We also report hydroxyproline concentrations in patients with metastatic bone disease and cirrhosis of the liver.