Methods for sterilizing a biocompatible hydrogel polymer are provided via treating the biocompatible hydrogel polymer with a supercritical CO2 treatment composition at a treatment pressure of about 4 MPa to about 30 MPa and a treatment temperature of about 5\xb0 C. If the total read out time of all of the pixels is shortened when effective pixels are thinned out to be read out without thinning out OB pixels, then the reset time period of each row is different from each other, and the problem of uneven charge accumulation time periods is caused. The strips, the strip reagent layer, or the methods may provide for the determination of a concentration value having at least one of a stability bias of less than \xb110% after storage at 50\xb0 C.