Sawita Khunchamnan, MD¹ , Naesinee Chaiear, MD¹^,² , Chatpong Ngamchokwathana, MD¹ , Tirachat Sewatanon, MD³ , Watchara Boonsawat, MD⁴

Background: Work-related asthma (WRA), including occupational asthma and work-exacerbated asthma, accounts for a substantial proportion of adult asthma cases. Although workplace surveillance aims to promote early detection, most cases are identified in clinical settings after symptom onset. Early recognition of occupational asthmagens/irritants in clinical practice is therefore essential. However, existing screening tools may inadequately capture specific occupational exposures, and workers often have difficulty identifying asthmagens/irritants.

Objective: 1) To develop a Thai questionnaire for occupational asthmagens/irritants identification in clinical settings. 2) To examine the content and face validity of the developed questionnaire.

Materials and Methods: This descriptive study included a literature review and review of existing resources, including the Occupational Asthma Web Application or OAKKU database of known asthmagens/irritants, to identify allergenic and irritant agents. A Thai version questionnaire was developed using occupation- and task-based exposure descriptions rather than chemical names alone. Content and face validity were assessed by six experts using item-level content validity index (I-CVI) and scale-level content validity index based on the average method (S-CVI/Ave). Pretesting was conducted among 30 adult patients with new-onset or worsening asthma and a history of occupational exposure from two tertiary hospitals in Thailand. Participants completed both the newly developed questionnaire and the existing Medical Surveillance of Occupational Asthma Questionnaire (MSOAQ) routinely used in the occupational medicine clinic at Srinagarind Hospital, and the identified exposures from the two instruments were compared.

Results: The final developed questionnaire comprised three sections: confirmation of asthma diagnosis, identification of asthmagen/irritant exposure, and screening for the likelihood of WRA. After two rounds of expert review, all items met predefined content validity criteria (I-CVI ≥0.83 and S-CVI/Ave ≥0.90). Face validity supported clarity and clinical applicability. During pretesting, task-based descriptions and practical examples facilitated greater recognition of asthmagen/irritant exposures compared with name-based items in the MSOAQ.

Conclusion: The developed questionnaire demonstrated good validity and improved identification of occupational asthmagens/irritants, supporting its use as a screening tool in clinical settings.

Received 9 March 2026 | Revised 9 April 2026 | Accepted 17 April 2026

J Med Assoc Thai 2026;109(6):538-46

DOI: 10.35755/jmedassocthai.2026.6.04402