#3028 Predictive validity of the Basel Assessment of Adherence to Immunosuppressive Medication Scale (BAASIS©) after renal transplantation
Authors: Haupenthal Frederik , Doberer Konstantin , Bauernfeind Florian , Gober Bettina , Ebenberger Katharina , Kainz Alexander , de Geest Sabina , Bond Gregor 
Published: May 2024

Abstract

Background and Aims
Adherence towards immunosuppressive medication is crucial for allograft survival after renal transplantation. However, its assessment in daily clinical practice remains challenging. The BAASIS© questionnaire, is a validated self-report instrument to detect non-adherence. However, its predictive validity for clinical relevant consequences of non-adherence needs to be established.

Method
The prospective AdTorque-trial (DRKS00026674) includes a consecutive cohort of 226 adult kidney graft recipients transplanted at the Medical University of Vienna between 01/2018 and 12/2019. Medication adherence was monitored up to two years by a multi-component assessment including the BAASIS©, electronic drug monitoring, pharmacy refill records, tacrolimus trough level, records by medical personal, individual evaluation by a transplant psychologist and concurrent immune monitoring by the quantification of Torque Teno virus load. The BAASIS© was applied at three-month intervals during the first year and at 24 months during routine follow-up visits. The adherence phases implementation and persistence were assessed by three items (i.e. taking, timing and dose-reduction) and one item of the BAASIS©. Non-adherence was defined by YES on any of these items. The primary clinical outcome was the occurrence of biopsy-proven allograft rejection during a maximum clinical follow-up of up to 4 years after transplantation. Herein we present the preliminary analysis of the multimodal monitoring focusing on the BAASIS© questionnaire.

Results
Of all 226 recipients (33% female, median age 57 years), 153 completed the adherence monitoring for 2 years, resulting in a total of 973 BAASIS© assessments. Non-adherence was reported at least once by 124 (55%) recipients and 67 recipients (30%) revealed non-adherence multiple times. The proportion of non-adherent recipients increased from 11% to 31% within the first three months and was between 27% to 32% at subsequent visits from month 6 to 24 post-transplant. Issues in the punctual timing of dose taking was the most frequent cause for non-adherence. During the clinical follow-up of 44 months (median, IQR 12-48), non-adherent recipients had a significantly higher rate of biopsy-proven rejection than adherent recipients (25%, n = 30 vs. 7%, n = 7; p &lt; 0.001). A time-dependent cox regression model showed that non-adherence assessed by the BAASIS© predicted an increased risk for allograft rejection (HR 2.87, 95% CI 1.47-5.6).

Conclusion
Medication non-adherence was substantially reported already in early phases post-transplant and was associated with an increased risk for allograft rejection. Our analysis demonstrated the predictive validity of the BAASIS©, a self-report instrument which can easily be integrated in daily transplant practice. Regular adherence assessments might identify patients at risk for poor clinical outcome due to medication non-adherence and provide rationale for intervention.