Following antiviral treatment , serum HCVcAg levels rapidly declined within the first week and correlated well with corresponding HCV RNA at baseline , weeks 4 , 12 , 24 , 48 and 72 ( rs = 0.969 , 0.928 , 0.999 , 0.983 , 0.985 and 0.946 , respectively , P < 0.001 ) .