The German Revised version of the Niigata PPPD Questionnaire (NPQ-R): Development with patient interviews and an expert Delphi consensus

BACKGROUND: Persistent postural-perceptual dizziness (PPPD) is a functional disorder of the nervous system and currently one of the most common types of chronic dizziness. Currently existing questionnaires do not fully assess patients’ specific symptoms of PPPD. The Japanese Niigata PPPD Questionnaire (NPQ) was recently developed following consensus-based diagnosis criteria. The aim of this study was to translate it into German, evaluate its content with the help of experts and patients and, if necessary, revise the original version to allow for a comprehensive assessment of patients’ PPPD-related symptoms. METHODS: A 3-round expert Delphi survey and semi-structured patient interviews were conducted. 28 experts from Switzerland, Germany and Austria working in hospitals or outpatient centres were asked to complete a first questionnaire on various aspects of PPPD, on the translated, original NPQ and their own related experiences (Round one), a second questionnaire with statements regarding PPPD they could agree or disagree with using a 6-point Likert-scale (Round two), and a third survey to finally reach a consensus on statements to be integrated into the NPQ. In addition, eleven patients (mean age of 64.6±12.6 years; 6 females) were selected according to the criteria for the diagnosis of PPPD proposed by the Bárány Society and participated in a semi-structured interview asking for their opinion on the content of the original NPQ. All collected data were analysed using a descriptive evaluation and a qualitative content analysis based on verbatim transcripts. RESULTS: Seven new items were added to the NPQ based on expert and patient comments and ratings. Its revised version (NPQ-R) comprises 19 items divided into five subscales using a 7-point Likert-scale with two additional subscales relating to associated symptoms and symptom behaviour in PPPD. The new maximal score is 114 points compared to 72 for the NPQ. CONCLUSION: The NPQ-R is the first patient-reported outcome measurement for patients with PPPD in German. It should help to provide a comprehensive assessment of the intensity of PPPD in affected patients.