Development and validation of an immunosuppressant therapy adherence barrier instrument.
BACKGROUND
To decrease allograft rejection as a result of non-adherence to immunosuppressant therapy (IST), a valid and reliable instrument that measures solid organ transplant patients' adherence barriers is needed.


METHODS
An immunosuppressant therapy barrier scale (ITBS) was developed to assess transplant patients' perceived barriers to IST adherence and was completed by 222 transplant patients who lived in Georgia, USA. A renal transplant population subset was used to test the ITBS reliability and validity. Scale reliability was estimated using Cronbach's alpha coefficient of internal consistency; scale dimensionality was assessed using principal components analysis. The criterion-related validity of the scale was assessed by relating subscale scores to adherence measures and graft rejection. Nomological validity was assessed by relating barrier subscales to specific patient factors.


RESULTS
Two subscales that represented 'controllable' and 'uncontrollable' barriers were found. Cronbach's alpha coefficients demonstrated acceptable reliabilities of 0.93, 0.86 and 0.91 for the 'uncontrollable' and 'controllable' subscales, and for the entire ITBS, respectively. The ITBS subscales correlated negatively with a self-reported measure of IST adherence, IST serum concentrations and IST pharmacy refill adherence rate (P<0.01). The 'uncontrollable barrier' subscale was positively correlated to kidney graft rejection (P<0.01), thus demonstrating the ITBS's validity. Males and older patients reported more adherence barriers (P<0.05).


CONCLUSIONS
The ITBS is a reliable and valid instrument that can be used to measure patients' perceived barriers to IST adherence.
Chisholm
Marie A
MA
University of Georgia College of Pharmacy, Medical College of Georgia School of Medicine, Augusta, GA 30912, USA. Mchishol@mail.mcg.edu
Lance
Charles E
CE
Williamson
Gail M
GM
Mulloy
Laura L
LL
D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001294:Attitude to Health; D015331:Cohort Studies; D004334:Drug Administration Schedule; D005260:Female; D005500:Follow-Up Studies; D006084:Graft Rejection; D006085:Graft Survival; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use*; D007676:Kidney Failure, Chronic / Q000175:diagnosis / Q000401:mortality* / Q000628:therapy; D016030:Kidney Transplantation / Q000009:adverse effects / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010349:Patient Compliance / Q000706:statistics & numerical data*; D011336:Probability; D012372:ROC Curve; D011795:Surveys and Questionnaires; D016019:Survival Analysis; D014181:Transplantation Immunology
D007166:Immunosuppressive Agents