Understanding what really helps to ensure access to diagnostic services in the Indian Public Health System: a realist synthesis of the Common Review Mission reports (2007-2021)

# Background In India, the National Health Mission (NHM) has been supporting the states in building an integrated public healthcare network across the levels of care. This effort has improved access to, and utilization of, diagnostic services at public healthcare facilities. To continually enhance citizens' ability to seek and avail quality and affordable services, it is imperative to take stock of various components of the diagnostic ecosystem that may be common or unique to states and understand their influence on equipping the health system. The objective of the study was to understand key health system factors augmenting or limiting access to diagnostic services and outcomes. # Methods Common Review Mission (CRM) reports between 2007 and 2021 were selected for the study. Data relevant to diagnostic services were retrieved using defined search terms. The data were segregated for each Indian state and categorized under the pre-determined themes: state-specific practices, key findings, and challenges. Analysis of the data was done iteratively to identify the themes emerging from the reports over the years. Each theme was analysed further to deduce context-specific enablers and barriers influencing access to diagnostic service delivery. # Results The major themes that emerged include (i) the approach to health systems strengthening, (ii) efficiency of procurement and distribution systems, (iii) infrastructure, (iv) modes of service delivery, (v) implementation of Free Diagnostic Service Initiative, Comprehensive Primary Health Care and Biomedical Equipment Management and Maintenance Program, and (vi) quality of care , and (vii) diagnostic service outcomes. # Conclusions In a complex adaptive system, access to diagnostic services depends on the concurrent strengthening of various health system components across the levels of care. The nation has strategized accessible, affordable and acceptable diagnostic services to achieve universal health coverage and care-continuum pathways. States need to leverage the existing mechanisms, assess their implementation, and arrive at feasible and sustainable solutions to strengthen access to diagnostic services.