Table 2.

Studies used as basis for the development of statements regarding questions on A) screening and diagnosis of dysphagia and B) dysphagia-related QoL and prognostic value of dysphagia in PD

A) Question	First author, y	Study design	Screening /Diagnostic test assessed	N. patients	Level of evidence
2.1 a 2.2. b	Ali, 1996	Case–control	VFSS and manometry	12	III
2.1 a	Bird, 1994	Cross-sectional	Clinical examination	16	IV
2.1 a	Hartelius, 1994	Cross-sectional	Questionnaire	258	II
2.1 a	Monteiro, 2014	Case–control	Spirometry and VFSS	30	IV
2.1 b	Buhmann, 2019	Case–control	FEES	118	IV
2.1 b	Claus, 2020	Case–control	FEES	200	III
2.1 b	Lam, 2007	Cross-sectional	Questionnaire, WST, and VFSS	45	I
2.1 b	Loureio, 2013	Case–control	Questionnaire	174	IV
2.1 b	Pflug, 2018	Case–control	FEES	122	I
2.1 b	Potulska, 2003	Case–control	Electromyography and esophageal scintigraphy	18	IV
2.1 b 2.2 b	Rodrigues, 2011	Cross-sectional	FEES	28	IV
2.1 b	Sampaio, 2014	Cross-sectional	FEES and voice recording	19	III
2.1 b	Troche, 2016	Cross-sectional	Voluntary and reflex cough and cough airflow (PEFR)	64	IV
2.1 c	Belo, 2014	Case–control	WST	10	IV
2.1 c	Buhmann, 2019	Case–control	Questionnaire	119	IV
2.1 c	Kalf, 2011	Cross-sectional	Questionnaire	178	IV
2.1 c	Manor, 2007	Cross-sectional	Questionnaire	57	III
2.1 c	Minagi, 2018	Case–control	WST, tongue pressure measurement	30	IV
2.1 c	Simons, 2014	Cross-sectional	Questionnaire	82	IV
2.1 c	Singer, 1992	Case–control	Questionnaire	48	IV
2.1 c	Vogel, 2017	Cross-sectional	Questionnaire	60	III
2.1 c	Volontè, 2002	Cross-sectional	Questionnaire	65	IV
2.2 a	Hegland, 2014	Case–control	Reflex cough testing	22	IV
2.2 a	Kanna, 2014	Case–control	WTS	100	IV
2.2 a	Mari, 1997	Cross-sectional	Questionnaire	27	II
2.2 a	Miller, 2009	Cross-sectional	WST	137	III
2.2 a	Miyazaki, 2002	Cross-sectional	WST	24	II
2.2 a	Monte, 2005	Cross-sectional	VFSS	27	IV
2.2 a	Pitts, 2010	Cross-sectional	PEFR and VFSS	58	III
2.2 a	Pitts, 2018	Cross-sectional	Tongue pressure measurement	28	IV
2.2 a	Silverman, 2016	Cross-sectional	PEFR	68	IV
2.2 a	Troche, 2014	Cross-sectional	Reflex cough testing and VFSS	20	IV
2.2 b	Alfonsi, 2007	Case–control	EKSS	28	IV
2.2 b	Argolo, 2015a	Cross-sectional	VFSS	69	IV
2.2 b	Argolo, 2015b	Cross-sectional	VFSS	71	IV
2.2 b	Bassotti, 1998	Case–control	Manometry	18	IV
2.2 b	Castell, 2001	Cross-sectional	Manometry	16	IV
2.2 b	Cosentino, 2020	Cross-sectional	Electrophysiological assessment of swallowing	19	IV
2.2 b	Ding, 2018	Cross-sectional	VFSS	116	III
2.2 b	Ellerston, 2016	Case–control	VFSS	34	IV
2.2 b	Ertekin, 2002	Case–control	Surface electromyography	58	III
2.2 b	Fuh, 1997	Cross-sectional	VFSS	19	IV
2.2 b	Gaeckle, 2019	Cross-sectional	VFSS	89	IV
2.2 b	Hammer, 2013	Cross-sectional	FEES	18	IV
2.2 b	Johnston, 1997	Case–control	VFSS and manometry	7	IV
2.2 b	Jones, 2016	Cross-sectional	VFSS	26	IV
2.2 b	Jones, 2018	Case–control	HRM	31	III
2.2 b	Kim, 2020	Cross-sectional	surface electromyography	14	IV
2.2 b	Lee, 2015	Case–control	VFSS	29	IV
2.2 b	Lee, 2019	Case–control	VFSS	23	IV
2.2 b	Moreau, 2015	Cross-sectional	VFSS	70	I
2.2 b	Nagaya, 1998	Case–control	VFSS	16	IV
2.2 b	Schiffer, 2019	Case–control	VFSS	68	IV
2.2 b	Stroudley, 1991	Cross-sectional	VFSS	24	III
2.2 b	Su, 2017	Cross-sectional	HRM	33	IV
2.2 b	Suttrup, 2017	Cross-sectional	HRM and FEES	65	IV
2.2 b	Taira, 2020	Cross-sectional	HRM	51	IV
2.2 b	Tomita, 2018	Case–control	VFSS	184	II
2.2 b	Wakasugi, 2017	Cross-sectional	VFSS	201	IV
2.2 b	Wang, 2017	Cross-sectional	EKSS	42	IV
2.2 b	Ws Coriolano, 2012	Cross-sectional	Surface electromyography	15	IV

B) Question	First author, y	Study design	Outcome measure	N. patients	Level of evidence
2.3 a 2.4 a	Akbar, 2015	Retrospective	Incidence of aspiration pneumonia; survival	5,665,710	I
2.3 a	Carneiro, 2014	Prospective	Impact of dysphagia on QoL	62	IV
2.3 a 2.4 a	Cilia, 2015	Retrospective	Survival, confinement to wheelchair or bed, fracture, PEG placement	401	II
2.3 a	Han, 2011	Prospective	Depression related to dysphagia	127	IV
2.3 a 2.3 b	Leow, 2010	Prospective	Impact of dysphagia on QoL	32	III
2.3 a 2.4 a	Lorefält, 2006	Prospective	Impact of dysphagia on QoL/Severity of dysphagia	26	IV
2.3 a 2.3 b	Manor, 2009	Prospective	Mood changes related to dysphagia	69	II
2.3 a	Miller, 2006	Retrospective	Impact of dysphagia on QoL	137	III
2.3 a	Plowman-Prine, 2009	Prospective	Impact of dysphagia on QoL	36	III
2.3 a	Silbergleit, 2012	Prospective	Impact of dysphagia on emotional changes	14	IV
2.3 a 2.3 b	Storch, 2013	Prospective	Impact of dysphagia on QoL	100	IV
2.3 a 2.3 b	Van Hooren, 2016	Prospective	Impact of dysphagia on emotional changes	100	IV
2.4 a	Auyeung, 2012	Retrospective	Survival	171	II
2.4 a	Fabbri, 2019	Retrospective and Prospective Cross-sectional	Survival, institutionalization	50	I
2.4 a	Hussain, 2018	Retrospective	Survival	51	III
2.4 a	Lo, 2009	Retrospective	Survival	573	II
2.4 a	Malmgren, 2011	Retrospective	Survival	191	III
2.4 a	Müller, 2001	Retrospective	Survival	17	II
2.4 a	Robbins, 2008	Prospective	Pneumonia	255	I
2.4 a	Barichella, 2013	Prospective	Nutritional status	208	I
2.4 a	Cereda, 2014	Retrospective	Non-motor symptoms	6462	IV
2.4 a	Goh, 2016	Retrospective	Pneumonia and choking	194	II
2.4 a	Lee, 2016	Prospective	Pneumonia	66	IV
2.4 a	Miller, 2009	Prospective	Impact of dysphagia on PD	137	III

Studies were classified according to various descriptors (e.g., study design, presence or not of a reference standard diagnostic test, sampling method, sample size, blinding, presence of clearly stated inclusion and exclusion criteria) according to the Classification of Evidence Schemes of the Clinical Practice Guideline Process Manual of the American Academy of Neurology ¹⁷. Each study was graded according to its risk of bias from Class I to Class IV (with I corresponding to the highest quality and IV to the lowest quality)

EKSS Electro-Kinesiologic Swallowing Study; FEES Fiberoptic endoscopic evaluation of swallowing; HRM High-resolution manometry; PEG Percutaneous Endoscopic Gastrostomy; PEFR Peak expiratory airflow rate; VFSS Videofluoroscopic study of swallowing; WST Water swallow test