An algorithm of three physician billing codes ( separated by at least 30days ) in 2years or one hospitalization had a sensitivity of 73.7 % ( 95 % confidence interval [ CI ] 64.8-82 .5 % ) , specificity of 99.8 % ( 95 % CI 99.6-99 .9 % ) , positive predictive value ( PPV ) of 79.5 % ( 95 % CI71.1-88 .0 % ) , and negative predictive value ( NPV ) of 99.7 % ( 95 % CI99.5-99 .8 % ) for identifying patients who had ever had epilepsy .