Development and Validation of the Healthcare Expenditure and Location Dynamics in Acute Febrile Illness (HEAL-AFI) Tool: A Community-Based Cohort Study With a Special Focus on Dengue and Chikungunya in the Urban Slum of Delhi, India

Introduction: Cost-of-illness (COI) studies quantify the economic burden of diseases, yet existing tools often lack standardized cost domains and contextual adaptation. We developed and validated the Cost of Healthcare Expenditure Questionnaire (CHEQ), a generic tool, and its adaptation for acute febrile illness (HEAL-AFI), tailored to dengue and chikungunya in Delhi slum communities. Methodology: Conducted in a resettlement colony of Northeast Delhi, this study followed a multistage process with five iterative rounds. Round 1 involved item generation after the literature review. In Round 2, eight experts assessed content validity using Lawshe’s method. Round 3 reassessed content validity and translated the tool. Round 4 tested face validity and feasibility among 32 participants and eight interviewers. Round 5 evaluated reliability via test-retest after 12 days using Cohen’s κ, intraclass correlation coefficients (ICCs), and Cronbach’s α. Data were collected on KoboCollect and analyzed in IBM SPSS Statistics for Windows, version 26.0. Results: Expert review retained 74 items for CHEQ (76 for HEAL-AFI), with CVI improving from 0.78 (Round 2) to 0.92 (Round 3). Face validity demonstrated good clarity and ease of use, with a mean administration time of 24.3 ± 5.1 minutes (T1) and 23.7 ± 4.8 minutes (T2). Reliability was substantial for categorical variables (κ = 0.63-0.79; agreement 72-84%) and excellent for continuous variables (ICC = 0.82-0.94). Internal consistency was high across domains (Cronbach’s α = 0.78-0.89). Conclusion: CHEQ and HEAL-AFI are validated, reliable, and feasible tools for capturing household healthcare expenditures. CHEQ provides a standardized framework across diseases, while HEAL-AFI contextualizes costs for acute febrile illnesses (AFIs) with geospatial integration. These tools can strengthen COI research and may guide equitable health policy.