highly significantP <0.001
Correlation between the main outcome measures There was a highly significant correlation between the results of the pill count and serum level methods with regard to the dichotomous outcome adherent/nonadherent ( P <0.001): 75% of the patients rated as nonadherent by means of pill count were also rated as nonadherent by serum blood levels, and 85.4% of the patients rated as adherent by means of the pill count were also rated as adherent by blood serum levels (phi=0.40, kappa=0.25, P <0.001).