Need for Community Specific Reference Intervals in Pulmonary Function Tests

Sir, It is our pleasure to read the case–control study – An observational study of respiratory dysfunction in Parkinson’s disease at a tertiary care hospital in Delhi by Ali et al.[1] published in April–June 2024 issue of the journal. While referring to the spirometric reference intervals (RIs) presented by Ranu et al.,[2] Ali et al.[1] found that Indian Parkinson’s disease (PD) patients had significantly greater respiratory dysfunction (RD) than controls, and RD was significantly higher with increasing PD severity. The authors have mentioned some of the limitations of the study which might debate the study results. We would like to mention another important limitation. It is preferable in a large community such as India that community-specific RI of pulmonary function tests (PFTs) be employed to interpret PFT readings for the community, and, interestingly, these RIs were designed for the Indian population in 2018.[3] In the study methodology, Ali et al.[1] surprisingly addressed that they referred to foreign standards of spirometric RI,[2] which were basically formulated for White populations, to analyze PFT readings in the study population rather than Indian standards.[3] Consequently, the study findings need cautious interpretations. Author contribution Design, concept, literature review, preparation and editing of the manuscript, and final approval. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.