Diagnostic delay of myositis: protocol for an integrated systematic review

Introduction Idiopathic inflammatory myopathies (IIM). described as 'inflammatory myositis', are a heterogeneous group of rare muscular autoimmune diseases characterised by skeletal muscle inflammation. Its complex characteristics with lack of accurate diagnostic tests, unified classification system and comprehensive widely used diagnostic criteria could lead to diagnostic delay. This study will review diagnostic delay in myositis and provide an overview and clearer insight of patients' experiences, causes and consequences of diagnostic delay in myositis. Methods and analysis The literature source will be a systematic search of PubMed/MEDLINE, Scopus, ProQuest and sources of grey literature, conducted from database inception to December 2021 without restrictions on publication date. All study types (qualitative and quantitative) except review articles, examining diagnostic delay, incorrect diagnosis, missed diagnosis or slow diagnosis of all types of myositis in all ages will be included. Evidence of patients' experiences associated with diagnostic delay will also be examined. Studies in languages other than English, German and Indonesian will be excluded. Outcomes will be diagnostic delay time, patients' experiences, and causes and consequences associated with diagnostic delay in myositis. Two review authors will independently screen the titles and abstracts of search results against the inclusion criteria. The Mixed Methods Appraisal Tool (MMAT) will be used to appraise selected studies. Two independent authors will extract data using a prepiloted data extraction tool. If sufficient quantitative data is available, a meta-analysis will be conducted along with subgroup analysis including pooled diagnostic delay in each type of myositis. Qualitative data will be analysed in line with meta-aggregation methods. If data is insufficient, a narrative synthesis will be conducted. Ethics and dissemination As this work is a systematic review, ethical approval was not required. Findings of the study will be disseminated through publications in peer-reviewed journals, conferences and symposia. PROSPERO registration number CRD42022289830.

Automated summary

This study aims to review the diagnostic delay in idiopathic inflammatory myopathies (IIM) and provide an overview of patients' experiences, causes, and consequences of diagnostic delay in myositis. The lack of accurate diagnostic tests and unified diagnostic criteria for IIM may lead to delays in diagnosis.