All that glisters is not gold: a comparison of electronic monitoring versus filled prescriptions--an observational study.
BACKGROUND
Poor compliance with antihypertensive medication is assumed to be an important reason for unsatisfactory control of blood pressure. Poor compliance is difficult to detect. Each method of measuring compliance has its own strengths and weaknesses. The aim of the present study was to compare patient compliance with antihypertensive drugs as measured by two methods, electronic monitoring versus refill compliance.


METHODS
161 patients with a diagnosis of hypertension for at least a year prior to inclusion, and inadequate blood pressure control (systolic blood pressure > or = 160 mmHg and/or diastolic blood pressure > or = 95 mmHg) despite the use of antihypertensive drugs, were included. Patients' pharmacy records from 12 months prior to inclusion were obtained. Refill compliance was calculated as the number of days for which the pills were prescribed divided by the total number of days in this period. After inclusion compliance was measured with an electronic monitor that records time and date of each opening of the pillbox. Agreement between both compliance measures was calculated using Spearman's correlation coefficient and Cohen's kappa coefficient.


RESULTS
There was very little agreement between the two measures. Whereas refill compliance showed a large range of values, compliance as measured by electronic monitoring was high in almost all patients with estimates between 90% and 100%. Cohen's kappa coefficient was 0.005.


CONCLUSIONS
While electronic monitoring is often considered to be the gold standard for compliance measurements, our results suggest that a short-term electronic monitoring period with the patient being aware of electronic monitoring is probably insufficient to obtain valid compliance data. We conclude that there is a strong need for more studies that explore the effect of electronic monitoring on patient's compliance.
Department of Epidemiology, University of Maastricht, Maastricht, The Netherlands. gwenn.wetzels@epid.unimaas.nl
Gwenn E C
GE
Wetzels
Patricia J
PJ
Nelemans
Jan S A G
JS
Schouten
Boris L G
BL
van Wijk
Martin H
MH
Prins
D000368:Aged; D000959:Antihypertensive Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D016303:Clinical Pharmacy Information Systems; D003266:Continuity of Patient Care; D011307:Drug Prescriptions; D004581:Electronics; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000188:drug therapy*; D008297:Male; D008509:Medication Systems; D008875:Middle Aged; D009426:Netherlands; D010349:Patient Compliance / Q000706:statistics & numerical data*; D010594:Pharmacies; D012646:Self Administration
D000959:Antihypertensive Agents