Agni in Ayurveda represents the vital force responsible for the digestion, metabolism, and transformation of substances in the human body, deeply embedded within ancient Indian medical philosophy and practice [1]. This concept is regarded as the cornerstone of health and disease, shaping a holistic understanding of the physiological balance and pathological disruptions through its nuanced roles: Jataragni (the digestive “fire” or “heat” principle), Dhatwagni (tissue-level metabolism), and Bhutagni (elemental metabolism) [2].

Some contemporary authors have proposed tentative correspondences between the concept of Agni and metabolic stages recognized in biochemistry. While Jataragni is analogous to enzymatic digestion (hydrolysis), which governs digestive enzymes, the mechanical breakdown of food, and absorption in the gastrointestinal tract, Dhatwagni corresponds to intermediary metabolism, which relates to tissue-specific metabolic activities (eg, liver, muscle) that transform absorbed nutrients for tissue building and energy. Bhutagni represents cellular metabolism (Krebs cycle). It reflects molecular processing at the cellular level, including mitochondria-driven metabolic pathways [3]. However, these remain hypothetical and require empirical testing.

Given the centrality of Agni in maintaining health, it becomes crucial to evaluate and assess its function accurately in clinical practice. Various Agni assessment tools have been developed by several researchers to gauge its state and influence on health. The initial search conducted for the published literature yielded several articles. The existing Agni assessment tools encompass questionnaires, clinical evaluations, and specific interventions, yet each face notable methodological and practical limitations that warrant systematic review. The diversity and developmental stages of these tools reflect ongoing efforts to operationalize the nuanced concept of Agni for clinical and research contexts. Yet, issues of standardization and psychometric rigor remain unresolved.

Among these, the Scale on Assessment of Agni, developed by Patil et al [4], is a physician-administered scale that assess digestive strength by administering a specific amount of ghee. Another tool for the assessment of Agni was developed by Eswaran et al [5]. It is an extensive questionnaire based on classical Ayurveda texts. The questionnaire employs a 5-point Likert scale for each question. One more Agni assessment tool, developed by Singh et al [6], has been used extensively in the field. It is a self-administered questionnaire aligning features with the 4 states of Jataragni. These existing instruments vary widely in the administration mode, length, and reported psychometric quality, with common gaps in content validity, factor structure, and feasibility testing.

Given these limitations and the central role of Agni in Ayurveda, a systematic review evaluating the psychometric properties, content clarity, and applicability of existing Agni assessment tools is essential to advance evidence-based clinical and research practice. This protocol outlines a rigorous approach to identify, appraise, and synthesize the validity, reliability, and practical utility of available tools, thereby addressing a critical gap and guiding the development of standardized, contextually relevant instruments that can strengthen interdisciplinary collaboration and clinical application. No previous systematic review of psychometric evidence for Agni assessment tools has been registered in PROSPERO.

The systematic review was formally initiated in October 2025, following a planning phase that commenced in January 2025. Data from eligible studies will be systematically extracted, tabulated, and narratively synthesized to capture tool characteristics, psychometric performance, and practical applicability. Results will be presented in detailed tables and figures that illustrate risk of bias assessments to facilitate interpretation. The final review, including data analysis and synthesis, is expected to be completed and published by November 2026.

This systematic review protocol, prepared in accordance with the PRISMA-P guidelines and the Cochrane Handbook for Systematic Reviews of Interventions, delineates a methodical approach to evaluating the psychometric properties and clinical applicability of existing Agni assessment instruments. Within the Ayurvedic framework, Agni constitutes a fundamental determinant of physiological equilibrium, metabolic efficiency, and overall health maintenance. Its proper functioning is considered essential for maintaining homeostasis and preventing pathological manifestations, whereas its derangement is a primary etiological factor in disease development [17]. Traditional approaches to Agni assessment emphasize comprehensive clinical observation, incorporating parameters such as appetite, food digestibility, excretory patterns, bodily vitality, complexion, and mental clarity [18]. In recent decades, scientific advancements have enabled the integration of traditional Ayurvedic observations with objective biomedical assessments, including metabolic profiling, enzymatic assays, calorimetric evaluation, and metabolic imaging techniques [19]. This confluence of traditional and contemporary methodologies has led to the development of quantitative Agni assessment scales that endeavor to align subjective Ayurvedic evaluations with measurable physiological correlates. The validity and reliability of these assessment tools are crucial to ensuring diagnostic consistency, research integrity, and therapeutic precision within Ayurveda. Despite their proliferation, there has been no systematic synthesis of evidence evaluating the psychometric soundness of these instruments, specifically their validity, reliability, responsiveness, and cross-cultural adaptability. Thus, this protocol aims to systematically identify, appraise, and synthesize available evidence on Agni assessment tools to determine their theoretical foundation, measurement quality, and empirical credibility. By adhering to a transparent, rigorous methodological framework, this review might provide a comprehensive evidence base to support the refinement, validation, and integration of Agni assessment scales in contemporary Ayurvedic research and clinical practice.

Further, the use of standardized evaluation frameworks such as COSMIN and QUADAS-2 will facilitate a structured appraisal of methodological quality, minimize bias, and enhance the reliability of findings. The COSMIN and QUADAS-2 frameworks were selected for their robust criteria in evaluating psychometric properties and diagnostic accuracy, respectively. COSMIN will assess the methodological quality of studies reporting validity and reliability, while QUADAS-2 will evaluate diagnostic tool performance, particularly addressing challenges such as the absence of a universal gold standard for Agni and variability in tool administration across diverse settings.

A key anticipated challenge in conducting this systematic review will be the potential heterogeneity among available studies in terms of design, population characteristics, and assessment procedures used across various Agni evaluation tools. Given that Agni assessment is inherently rooted in Ayurvedic theoretical constructs, differences in the interpretation, operationalization, and measurement of Agni parameters may impede direct comparisons and meta-analytic synthesis. Furthermore, the absence of a universally recognized gold standard for Agni assessment poses limitations in establishing criterion validity and benchmarking the psychometric performance of individual tools.

Beyond these primary concerns, several additional methodological and interpretive challenges may arise. Publication bias remains a notable risk, as studies with favorable psychometric results are more likely to be published, potentially inflating the perceived robustness of specific instruments. Similarly, limited generalizability may limit the applicability of the findings. Variability in the conceptual definitions of Agni across classical Ayurvedic texts, as well as in its practical interpretation by different schools of thought, can further contribute to inconsistencies in the study outcomes. Regional and linguistic differences in Ayurveda education and practice may also influence item formulation, response interpretation, and tool validation. Moreover, small sample sizes, limited cross-validation, and inadequate reporting of psychometric testing protocols may constrain the reliability of conclusions drawn from the existing evidence base.

To address these challenges, the review will adopt several mitigating strategies. Comprehensive and systematic search methods, along with rigorous inclusion and exclusion criteria, will be applied to ensure methodological consistency and comparability across studies. Where possible, subgroup analyses will be conducted to explore heterogeneity based on population demographics, geographic regions, and variations in Ayurvedic interpretation. In addition, explicit documentation of theoretical definitions and measurement models of Agni in each included study will be maintained to enhance transparency and facilitate conceptual synthesis. Upon completion of the systematic review, patient and public involvement representatives will review the plain-language summary to ensure cultural appropriateness and linguistic equity.

This systematic review will provide a comprehensive understanding of the methodological quality and empirical robustness of existing Agni assessment tools, addressing a critical gap in standardized diagnostic methods in Ayurveda. Standardizing Agni assessment has significant relevance for national digital health efforts, as validated tools can be meaningfully integrated into the Ayushman Bharat Digital Health Mission to support interoperable, patient-centered Ayurvedic health records. Building on the findings of this review, we also propose initiating a Delphi consensus process to establish minimum psychometric standards for future Agni assessment instruments, thereby promoting methodological rigor and consensus across the field. To ensure transparency and accessibility, the review results, datasets, and related materials will be shared through open-access publication and deposited on Zenodo. Finally, the outcomes of this review will inform the design of a subsequent empirical validation study using the top-ranked tool, advancing the development of reliable, clinically relevant, and widely applicable frameworks for Agni assessment in Ayurveda.

One of the limitations of this study is its restriction to English-language publications. While this may lead to the exclusion of relevant evidence, the studies published in English will be chosen to ensure methodological consistency in data extraction, minimize the risk of misinterpretation of psychometric concepts during translation, and maintain feasibility, given the resource constraints for multilingual screening and appraisal.