Introduction: The Nijmegen questionnaire (NQ) has previously been used for screening the hyperventilation syndrome (HVS) in asthmatics. However, no validity study has been reported so far.
Objective: To examine the validity and reliability of the NQ in asthma patients and identify the prevalence of HVS.
Methods: The NQ (n = 162) was examined for translation, construct, cross-sectional and discriminant validity as well as for internal consistency and test-retest reliability.
Results: Principal component analysis and exploratory factor analysis revealed a single factor solution with 11 items and 58.6% of explained variability. These 11 NQ items showed high internal consistency (Cronbach's alpha = 0.92) and test-retest reliability (IR = 0.98). Higher NQ scores were found in the following subgroups: women versus men (p < 0.01); participants with moderate versus mild asthma (p < 0.001) or uncontrolled versus controlled asthma (p < 0.001), and participants with breath-hold time (BHT) < 30 versus ≥ 30 s (p < 0.01) or end-tidal CO2 (ETCO2) ≤ 35 versus >35 mmHg (p < 0.001). A cut-off score of >17 discriminated the participants with regard to the presence of HVS. The NQ showed 92.73% sensitivity and 91.59% specificity. The total NQ score was found significantly correlated with ETCO2 (r = -0.68), RR (r = 0.66) and BHT (r = -0.65). The prevalence of HVS was found 34%.
Conclusion: The NQ is a valid and reliable questionnaire for screening HVS in patients with stable mild-to-moderate asthma.
Keywords: Hyperventilation; Nijmegen questionnaire; reliability; validity.