The Nijmegen Questionnaire: A valid measure for hyperventilation syndrome

Hyperventilation syndrome is often undiagnosed due to its multi-systemic and 5 apparently unrelated symptoms. The Nijmegen Questionnaire is used by clinicians to 6 assess susceptible individuals, based on self-reporting symptoms attributed to 7 hyperventilation syndrome. However, evidence of psychometric properties of this 8 questionnaire is lacking. This study investigated two types of validity, using 9 interviews and Rasch analysis. Data showed that the Nijmegen Questionnaire met 10 criteria for content validity but not for structural validity. Content validity was 11 supported by a high matching percentage between the symptoms identified within 12 interview data and the current items on the Nijmegen Questionnaire (94%). Reported 13 symptoms from study participants were conceptually congruent with most of the 14 questionnaire items with minor language inconsistencies between patients and 15 clinicians. Rasch analysis indicated a poor fit of the Nijmegen Questionnaire to the 16 Rasch model, demonstrating poor structural validity. This study also developed a 17 revised version of the Nijmegen Questionnaire, which did meet criteria for structural 18 validity. Subsequently, a conversion table was created for transforming raw total 19 scores of the questionnaire in the clinical and research settings. Physiotherapists 20 should use the revised 15-item Nijmegen Questionnaire for clinical and research 21 purposes since it provides more accurate representation of the severity of patients’ 22 symptoms than the original scoring.