Initial development and testing of an instrument for patient self-assessment of adverse drug reactions.
OBJECTIVE
To develop and conduct preliminary testing of a causality assessment tool for patients, for potential use in encouraging both discussions with clinicians about suspected adverse drug reactions (ADRs) and reporting to authorities.


METHODS
Ten causality statements, developed from qualitative studies involving patients, with a scoring system allowing categorization, were embedded in a questionnaire which also included a symptom checklist and additional details about one suspected ADR and medicine, selected for causality assessment. Patients with experiences of suspected ADRs were involved in cognitive interviews (15), piloting (20) and psychometric testing (120). Test-retest reliability, construct validity and criterion-related validity were evaluated, through repeated causality assessment, comparison with a visual analogue scale assessing certainty of causality and comparison with causality assessment using World Health Organization-Uppsala Monitoring Centre (WHO-UMC) criteria, respectively. The study involved outpatients at a university hospital in northeast Thailand.


RESULTS
Ninety-eight patients completed causality assessment twice: both causality scores (Spearman rs  = 0.715; p < 0.001) and causality classification [percentage of positive agreement (PPA) = 68.4; κ = 0.419; p < 0.001] showed satisfactory reliability. Causality scores were positively correlated with certainty of causality (Spearman rs  = 0.556; p < 0.01). There was moderate agreement against WHO-UMC criteria [PPA = 70.4; κ = 0.440; p < 0.001]. Of the 91 completing an evaluation, 88% agreed that the tool should be used routinely, 78% agreed that it gave them useful results and 80% agreed that it was easy to use.


CONCLUSIONS
This novel instrument has satisfactory psychometric properties and was acceptable to Thai patients, but it requires further testing. It has potential for use in supporting patients with suspected ADRs to discuss these with health professionals, and perhaps to report directly.
Division of Clinical Pharmacy, Faculty of Pharmaceutical Sciences, Khon Kaen University, Khon Kaen, Thailand.
Narumol
N
Jarernsiripornkul
Division of Clinical Pharmacy, Faculty of Pharmaceutical Sciences, Khon Kaen University, Khon Kaen, Thailand.
Nataporn
N
Chaipichit
Department of Internal Medicine, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
Thongchai
T
Pratipanawatr
Division of Clinical Pharmacy, Faculty of Pharmaceutical Sciences, Khon Kaen University, Khon Kaen, Thailand.
Verawan
V
Uchaipichat
Medway School of Pharmacy, The Universities of Greenwich and Kent at Medway, Kent, UK.
Janet
J
Krska
D016907:Adverse Drug Reaction Reporting Systems / Q000458:organization & administration* / Q000706:statistics & numerical data*; D015984:Causality; D059026:Diagnostic Self Evaluation; D064420:Drug-Related Side Effects and Adverse Reactions / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D010865:Pilot Projects; D011594:Psychometrics; D011795:Surveys and Questionnaires; D013785:Thailand / Q000453:epidemiology
adverse drug reactions; causality assessment; patient self-reporting; pharmacoepidemiology; psychometric evaluation; questionnaire