Reliability and Validity of the Iranian Version of Nijmegen Questionnaire in Iranians with Asthma

The aim of this study was to assess the validity and reliability of Nijmegen questionnaire (NQ) translated to Farsi for diagnosis of the hyperventilation syndrome (HVS) in patients with asthma.

The original version of NQ was translated to Farsi and then back-translated to English again to assess its agreement with the original version. To determine its cultural adaptation, a pilot study was carried out. The mean score of the questionnaire and the mean pressure of end tidal carbon dioxide (PETCO2) were compared in 100 asthmatic patients to determine the validity of the questionnaire. For reliability, 52 out of 100 patients randomly filled out the questionnaire with an interval of 5 to 10 days. Internal consistency and content validity of the questionnaire were assessed by Cronbach's alpha coefficient and by calculating floor and ceiling effects respectively. The exploratory factor analysis was used to assess the factor structure.

There was a significant inverse correlation between NQ scores and PETCO2 (P=-0.783). Cronbach's alpha coefficient was greater than 0.7, indicating good internal consistency of the questionnaire (P=0.702). The questionnaire had a good stability in an interval of 5 to 10 days (P=0.826). The NQ had no floor and ceiling effect. and also factor analysis of 16 scales showed that this questionnaire has a five-factor structure, which can describe 55% of data variance.

The Iranian version of the Nijmegen questionnaire is a valid and reliable tool for detection of patients with HVS. In addition, the questionnaire can be used to evaluate the condition of respiratory function in people with asthma.