Validity of the Nijmegen questionnaire for screening hyperventilation syndrome in primary care

Background: The Nijmegen questionnaire (NQ), commonly used to screen hyperventilation syndrome (HVS), was validated in 1985 (Sen/Sp:0.91/0.95 - PPV/NPV:0.94/0.92) in subjects identified with HVS (HVS+) on the basis of complaints from which patients with somatic disorders were voluntarily excluded. Authors emphasized that the qualities of the NQ might vary depending on the disorders encountered. Aim: We aimed to review the psychometric properties of the NQ including HVS+ and controls (HVS-) with/without somatic disorders. Methods: The NQ was completed by 112 HVS+ identified with a positive Hyperventilation Provocation Test and by 212 HVS- including 88 healthy subjects and 124 patients suffering from COPD(N=34), asthma(N=28), gastric(N=15), thyroid(N=11), psychologic/neurologic(N=6) disorders. Structural and content validities, together with predictive properties were estimated. Results: The component analysis confirmed 3 previously identified components encompassing 53% of the total variance (S2), characterized as "respiratory symptoms" (S2=38%;αCR=0.84), "central/peripheral symptoms" (S2=8%;αCR=0.72) and "general anxiety" (S2=7%;αCR=0.68). An excellent AUC[CI95%]=0.89[0.85;0.93], confirming a positive threshold NQ score of ≥23/64, revealed Sen/Sp of 0.86/0.79 and PPV/NPV of 0.69/0.91 less than originally described. Misclassification concerned 14% of HVS+ (FN) and 21% of HVS- (FP). Among the latter, 38% of COPD, 29% of asthmatic and 17% of cardiac patients were FP. Conclusion: In the context of a primary care setting, the NQ might demonstrate lower predictive properties than expected. We therefore recommend the use of the Hyperventilation Provocation Test in HVS screening to confirm a positive NQ.