# Implementation fidelity of a pharmacist-led intervention program to improve a high serum phosphate concentration in haemodialysis patients: a mixed-methods study

## TL;DR

A pharmacist-led program to reduce high phosphate levels in dialysis patients had mixed success, with high adherence to the intervention but limited impact on phosphate levels.

## Contribution

This study evaluates the implementation fidelity of a pharmacist-led intervention to manage high phosphate levels in haemodialysis patients using mixed methods.

## Key findings

- The intervention showed moderate to high adherence, except for the screening process.
- Four themes influencing implementation fidelity were identified: patient knowledge, correct PBM use, treatment individualization, and pharmacist-patient relationships.
- Improving patient selection and targeting those with higher phosphate levels could enhance intervention effectiveness.

## Abstract

The PIDO-P (Pharmacist Intervention and Dose Optimization of Phosphate-binding medication) was designed to improve high serum phosphate concentration (SPC) in haemodialysis patients with a high pill burden of phosphate-binding medication (PBM). This intervention consisted of three pharmacist-patient consultations, in which barriers to adherence to PBM were addressed and PBM dose was reduced. Although this intervention improved PBM adherence, SPC remained high.

To determine the implementation fidelity (IF) of the PIDO-P intervention.

This mixed-methods implementation study had a convergent design using the intervention mixed-methods framework. Data from all patients included in the PIDO-P study (n = 75) were used to assess IF using Carroll’s Framework for IF. Six key components were identified [A: identifying barriers, B: assessing medication-related health literacy; C: providing information and advice, D: discussing patient preferences, E: providing a summary/dose reduction advice, F: performing a follow-up consultation]. Two researchers independently rated the extent to which the different aspects of the key intervention components were carried out as planned. Data sources were research administration (quantitative and qualitative), oral surveys from patients (quantitative and qualitative) and pharmacists (quantitative), semi-structured interviews with six patients, two pharmacists, and three prescribers (qualitative), and electronic medical records (quantitative). Data from semi-structured interviews were thematically analysed according to Braun and Clarke with Atlas.ti, quantitative data were analysed using descriptive statistics in SPSS. Where possible, data integration was performed.

The adherence to the intervention was moderate to high, except for the screening process. The written summary was delivered to a moderate degree (65.3%). Facilitation strategies were helpful, and pharmacists considered the intervention not too complex. The quality of delivery and participant responsiveness were good. Four IF themes could be identified: (1) patient knowledge and understanding, (2) correct use of PBM, (3) PBM treatment individualisation, (4) relationship between pharmacist and patient. To increase its feasibility, the intervention should be targeted at patients with SPC > 2.0 mmol/L, and patient selection should be improved.

The lack of effect of the PIDO-P intervention on SPC cannot be explained by low IF. Targeting patients with higher SPC and improving patient selection may increase its effectiveness.

The online version contains supplementary material available at 10.1007/s11096-025-01995-z.