Multiple chemical sensitivity (MCS) validity, prevalence, tools and interventions: systematic review protocol.

INTRODUCTION

Multiple chemical sensitivity (MCS) describes reported adverse reactions to exposure to common chemical agents (solvents, odourants, air pollutants, material or substances) in low doses tolerated by most people. Symptoms involve more than one organ system and responses are triggered by multiple, chemically unrelated substances.

METHODS AND ANALYSIS

The systematic review will aim to answer six questions: Which definitions of MCS have been validated? What is the diagnostic performance of tools for identifying MCS? What is the prevalence and incidence of MCS? What is the empirical evidence that MCS is a distinct disorder? What is the empirical evidence for underlying biological mechanisms for MCS? What are the effectiveness and safety of treatment and management strategies for MCS?We will conduct a comprehensive search in 22 multidisciplinary databases for primary and secondary research, research registries and clinical practice guideline repositories. We will reference-mine reviews and included studies, and confer with experts. Screening will be conducted in duplicate against prespecified eligibility criteria. Data abstraction will be pilot tested using detailed data abstraction forms to ensure accuracy and minimise ambiguity. Critical appraisal will be specific to the key question. We will synthesise data in comprehensive tables and figures. Where possible, meta-analysis will use random effects models to determine effect sizes.

ETHICS AND DISSEMINATION

This study was determined to be exempt from review (UP-22-00516). The results will be disseminated through a journal manuscript, and the data will be publicly accessible through an online data repository.

PROSPERO REGISTRATION NUMBER

CRD420250645577.