# Multiphase optimization implementation strategy for tobacco cessation interventions in primary care clinics: A cluster-randomized type 3 hybrid effectiveness-implementation trial

## TL;DR

This study aims to improve smoking cessation interventions in Chinese primary care clinics by testing the best implementation strategies using a multi-phase approach.

## Contribution

The study introduces a customized, optimized implementation strategy for BISC using the MOST framework in a low- and middle-income country context.

## Key findings

- A factorial trial will test the effectiveness of four implementation strategies in primary healthcare clinics in Guangdong, China.
- The study uses MOST to identify the most efficient components of multi-faceted implementation strategies for BISC.
- Blinding of assessors and analysts will help ensure unbiased evaluation of implementation and effectiveness outcomes.

## Abstract

Brief verbal intervention for smoking cessation (BISC) is an evidence-based practice proven to be effective and cost-efficient, yet its implementation in primary healthcare (PHC) clinics in China is currently inadequate. Developing and evaluating multifaceted implementation strategies are crucial to translating such evidence-based practices into routine clinical care. This study protocol outlines a rigorous, multi-phase approach to identifying and testing the most effective strategies for BISC implementation. This is a two-phase study utilizing the Multiphase Optimization Strategy (MOST). The first phase, which has been completed, involved using a scoping review, stakeholder consultations, and a Best-Worst Scaling (BWS) online survey to systematically identify and define four key implementation strategies. The second phase is a cluster-randomized 2×2×2 factorial trial conducted in primary healthcare institutions in Guangdong province, China, from January 2026 to December 2026. Eligible participants are clinicians providing primary healthcare services. Clusters will be randomly assigned, and outcome assessors and data analysts will be blinded to allocation. Data collection includes unannounced standardized patient (USP) visits, questionnaires, interviews, and telephone follow-ups, with outcomes assessed six months after the endline. The study's outcomes are categorized into a primary aim (implementation outcomes) and a secondary aim (effectiveness outcomes). This protocol outlines the utilization of the MOST framework to customize the optimized combination of implementation techniques for BISC within the local context. By using a factorial design, the study could unpack the black box of multi-component interventions and identify which specific components are most effective and efficient. This approach is expected to provide a valuable methodological paradigm for advancing implementation science in low- and middle-income countries.

The study is registered on the official website of Chinese Clinical Trials

ChiCTR2600115994

BISC: brief verbal intervention for smoking cessation, PHC: primary healthcare, CFIR: Consolidated Framework for Implementation Research, BWS: best-worst scaling, MOST: Multiphase Optimization Strategy, USP: unannounced standardized patient, PSU: primary sampling unit, SSU: secondary sampling unit, PPS: probability proportional to size, DSMB: Data and Safety Monitoring Board, IOF: Implementation Outcomes Framework, PSAT: Program Sustainability Assessment Tool, PRESS: Provider Report of Sustainment Scale, NPT: Normalization Process Theory, EBP: evidence-based practice