title: The validity of self-reported primary adherence among Medicaid patients discharged from the emergency department with a prescription medication.
abstract: OBJECTIVE
  We determine the validity of self-reported prescription filling among emergency department (ED) patients.
  
  
  METHODS
  We analyzed a subgroup of 1,026 patients enrolled in a randomized controlled trial who were prescribed at least 1 medication at ED discharge, were covered by Medicaid insurance, and completed a telephone interview 1 week after the index ED visit. We extracted all pharmacy and health care use claims information from a state Medicaid database for all subjects within 30 days of their index ED visit. We used the pharmacy claims as the criterion standard and evaluated the accuracy of self-reported prescription filling obtained during the follow-up interview by estimating its sensitivity, specificity, positive likelihood ratio and negative likelihood ratio tests. We also examined whether the accuracy of self-reported prescription filling varied significantly by patient and clinical characteristics.
  
  
  RESULTS
  Of the 1,635 medications prescribed, 74% were filled according to the pharmacy claims. Subjects reported filling 90% of prescriptions for a difference of 16% (95% confidence interval [CI] 14% to 18%). The self-reported data had high sensitivity (0.96; 95% CI 0.95 to 0.97) but low specificity (0.30; 95% CI 0.26 to 0.34). The positive likelihood ratio (1.37; 95% CI 1.29 to 2.46) and negative likelihood ratio (0.13; 95% CI 0.09 to 0.17) tests indicate that self-reported data are not a good indicator of prescription filling but are a moderately good indicator of nonfulfillment. Several factors were significantly associated with lower sensitivity (drug class and over-the-counter medications) and specificity (drug class, as needed, site and previous ED use).
  
  
  CONCLUSIONS
  Self-reported prescription filling is overestimated and associated with few factors.
authors.affiliation: Department of Health Policy, George Washington University, Washington, DC, USA.
authors.forename: Ru
authors.initials: R
authors.lastname: Ding
authors.forename: Scott L
authors.initials: SL
authors.lastname: Zeger
authors.forename: Donald M
authors.initials: DM
authors.lastname: Steinwachs
authors.forename: Melinda J
authors.initials: MJ
authors.lastname: Ortmann
authors.forename: Melissa L
authors.initials: ML
authors.lastname: McCarthy
mesh_terms: D000293:Adolescent; D000328:Adult; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008484:Medicaid / Q000706:statistics & numerical data; D055118:Medication Adherence / Q000523:psychology; D008875:Middle Aged; D010351:Patient Discharge / Q000706:statistics & numerical data*; D010353:Patient Education as Topic / Q000379:methods; D055656:Prescriptions / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D057566:Self Report / Q000592:standards; D014481:United States / Q000453:epidemiology; D055815:Young Adult; D016903:Drug Monitoring