A method predicts an amount of an analyte in a urine specimen collected in a target time zone. The method includes measuring an amount of an analyte in a urine specimen collected in a predetermined time zone after an administration of a chelating agent and b) predicting, from the measured amount of the analyte in the urine specimen collected in the predetermined time zone, the amount of the analyte in the urine specimen collected in the target time zone on the basis of a correlation between amounts of analyte in urine specimens in the predetermined time zone and amounts of analyte in urine specimens in the target time zone. The amounts of the analyte in the urine specimens in the predetermined time and the target time zone are measured before predicting the amount of the analyte in the urine specimen collected in the target time zone.