The first two actuations within the first three sets of the day were defined as prescribed actuations while all other actuations were considered nonprescribed actuations. Percentage of prescribed actuations was calculated as the ratio of prescribed actuations to total actuations. A measure of percent-adherent days was derived by dividing the sum of the number of days participants used their inhaler in a clinically acceptable manner by the number of days the NC was available for use. An adherent day was defined as a day that contained two, three, or four sets with at least two of the sets containing two or three actuations. If any set contained five or more actuations, the day was considered nonadherent.
Statistical Analyses
Nebulizer Chronolog data from the first 4-month follow-up were used to compare the feedback and control groups on the following adherence measures: sets per day, actuations per set, percentage of prescribed actuations, and percentage of adherent days. The groups were also compared with respect to the accuracy of self-reported usage as validated by the NC. Unpaired t tests (two-tailed) and x2 tests were used for the analyses. Probability values less than 0.05 were considered statistically significant.
Results
Clinical Information
Of the 140 feedback and 111 control participants assigned NCs, 13 did not return for the first 4-month follow-up visit and 1 transferred to another clinical center, leaving 237 participants (134 feedback and 103 control subjects) whose NCs were returned. Twenty-seven NCs could not be read due to battery failure or data retrieval problems. Two additional participants were excluded because their 4-month follow-up visit occurred less than 30 days after the NC was issued, leaving a total study group of 205 (116 feedback and 89 control subjects). Sixty percent of the sample was male, and the mean age was 49.6 years. Whites comprised 97.6 percent of the sample with African-Americans comprising the other 2.4 percent.