Patent ID: 7569184

Claim:
A method for determining the level of an analyte in blood from a solution formed from a dried blood fluid specimen, said blood fluid specimen being a plasma or serum specimen, comprising: in either order, measuring the analyte level in said solution and measuring the level of at least one normalizing analyte; and determining the analyte level in the blood from which said blood fluid specimen was collected based on said analyte level in said solution and on the level of said normalizing analyte in said solution, wherein, in determining the analyte level in the blood from which said blood fluid specimen was collected, a recovery delta is added to the analyte level of the analyte level in said solution to provide a recovery delta corrected solution analyte level, and the analyte level in the blood from which said blood fluid specimen was collected is determined as a function of said recovery delta corrected solution analyte level and on the level of said normalizing analyte, wherein said recovery delta is a positive value, wherein said recovery delta is determined as a function of the time elapsed since said blood fluid specimen was collected.