Objectives: Many questionnaires on adherence to antiretroviral therapy are in use, but the validity of patients’ responses has not been tested. The Medication Adherence Self-Report Inventory (MASRI) has been developed and tested for its validity against objective measures and treatment outcome.
Design: Prospective study comparing questionnaire responses with MEMS TrackCap (MC, a medication event monitoring system), pill count (PC) and plasma HIV viraemia in a publicly funded specialist HIV clinic.
Participants: Patients self-medicating antiretroviral therapy who were not cognitively impaired and were able to read and understand English.
Results: Mean adherence by MC of the 78 subjects was 92.9% (SE, 1.8%) and by PC 96.8% (SE, 1.4%). Agreement between MC and responses to items about doses missed 1, 2 or 3 days ago was low (κ = 0.23 (P < 0.03), 0.44 (P < 0.001) and 0.28 (P < 0.01) respectively). This improved when these responses were summated (κ = 0.46;P < 0.001) and was similar to that for recall of non-adherence over the preceding 2 weeks (κ = 0.54;P < 0.001). Mean self-reported adherence by visual analogue scale (VAS) over the preceding month was 93.3% (SE, 1.2%). This was strongly associated with both MC (r = 0.63;P < 0.001) and PC (r = 0.75;P < 0.001). On multivariate analysis, the strongest association between a MASRI item and MC was for the VAS. Both the 2 week recall and VAS items were inversely associated with viral load (P = 0.01). There was no association between dose timing (measured MC or questionnaire) or 3 day self-report and viral load.
Conclusions: The MASRI provides a means of measuring patient adherence that is valid when compared with objective measures.
From the St Stephen's Centre, Chelsea and Westminster Hospital, London, UK.
Requests for reprints to: Dr J. C. Walsh, St Mary's Hospital, Praed Street, London W2 1NY, UK.
Received: 23 November 2000;
revised: 13 August 2001; accepted: 30 August 2001.
Sponsorship: the MEMS TrackCaps was supported by Roche Products Ltd, UK.