title: Examining assumptions regarding valid electronic monitoring of medication therapy: development of a validation framework and its application on a European sample of kidney transplant patients.
abstract: BACKGROUND
  Electronic monitoring (EM) is used increasingly to measure medication non-adherence. Unbiased EM assessment requires fulfillment of assumptions. The purpose of this study was to determine assumptions needed for internal and external validity of EM measurement. To test internal validity, we examined if (1) EM equipment functioned correctly, (2) if all EM bottle openings corresponded to actual drug intake, and (3) if EM did not influence a patient's normal adherence behavior. To assess external validity, we examined if there were indications that using EM affected the sample representativeness.
  
  
  METHODS
  We used data from the Supporting Medication Adherence in Renal Transplantation (SMART) study, which included 250 adult renal transplant patients whose adherence to immunosuppressive drugs was measured during 3 months with the Medication Event Monitoring System (MEMS). Internal validity was determined by assessing the prevalence of nonfunctioning EM systems, the prevalence of patient-reported discrepancies between cap openings and actual intakes (using contemporaneous notes and interview at the end of the study), and by exploring whether adherence was initially uncharacteristically high and decreased over time (an indication of a possible EM intervention effect). Sample representativeness was examined by screening for differences between participants and non-participants or drop outs on non-adherence.
  
  
  RESULTS
  Our analysis revealed that some assumptions were not fulfilled: 1) one cap malfunctioned (0.4%), 2) self-reported mismatches between bottle openings and actual drug intake occurred in 62% of the patients (n = 155), and 3) adherence decreased over the first 5 weeks of the monitoring, indicating that EM had a waning intervention effect.
  
  
  CONCLUSIONS
  The validity assumptions presented in this article should be checked in future studies using EM as a measure of medication non-adherence.
authors.affiliation: Institute of Nursing Science, University of Basel, Bernoullistrasse 28, 4056, Basel, Switzerland. kris.denhaerynck@unibas.ch
authors.forename: Kris
authors.initials: K
authors.lastname: Denhaerynck
authors.forename: Petra
authors.initials: P
authors.lastname: Schäfer-Keller
authors.forename: James
authors.initials: J
authors.lastname: Young
authors.forename: Jürg
authors.initials: J
authors.lastname: Steiger
authors.forename: Andreas
authors.initials: A
authors.lastname: Bock
authors.forename: Sabina
authors.initials: S
authors.lastname: De Geest
mesh_terms: D000328:Adult; D000465:Algorithms; D016903:Drug Monitoring / Q000295:instrumentation / Q000592:standards*; D004349:Drug Packaging / Q000295:instrumentation; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use*; D007407:Interviews as Topic; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D010349:Patient Compliance / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D013557:Switzerland
chemical_list: D007166:Immunosuppressive Agents