Figure 5

Variation of the difference of PHT _free and PHT _{adj_free} with respect to various independent variables. (A) Distribution of the difference between PHT _free and PHT _{adj_free} separated between males and females. Each dot represents a single timepoint of data with a total of 1,020 datapoints from male patients and 733 datapoints from female patients. The solid horizontal lines indicate the mean difference. There was no significant difference between males and females (unpaired t-test > 0.05). (B) Distribution of the difference between PHT_free and PHT_{adj_free} separated by the days in between the albumin and total phenytoin measurements (that allowed for PHT_{adj_free} calculation). Each dot represents a single timepoint of data with a total of 1,753 datapoints (559 datapoints for 0 days difference between albumin and PHT_total determination, 290 for 1 day difference, 215 for 2 days difference, 190 for 3 days difference, 152 for 4 days difference, 103 for 5 days difference, 112 for 6 days difference, and 132 for 7 days difference). The solid horizontal lines indicate the mean difference. There was no significant difference across days between albumin and phenytoin measurements (ANOVA P value > 0.05). (C) Distribution of the difference between PHT_free and PHT_{adj_free} separated into categories of patient location at time of laboratory ordering of PHT_total and PHT_free. 'Adult inpatient' and 'Peds inpatient' encompass all inpatient locations excluding intensive care units (ICUs), with adult defined as age 15 or older. 'All other locations' encompasses outpatient clinics, emergency room, and scheduled draws at hospital phlebotomy stations. (D) Distribution of the difference between PHT_free and PHT_{adj_free} separated into years in which the laboratory measurements were performed. There was a significant effect of patient location at time of PHT measurements (ANOVA P value < 0.0001)