Table 1.

Descriptive features of the 117 eligible studies included in the evaluation of screening, diagnosis, QoL and prognosis

Topic domain	All studies	Number of patients = number of studies	Cross-sectional/prospective studies	Case–control/retrospective study	Class of evidence
	N	N	N	N	N
Screening and diagnosis of dysphagia in PD	82	< 10 pts = 1 10–19 pts = 16 studies 20–50 pts = 28 studies  > 50 pts = 37 studies	58	24	4 Class I 4 Class II 18 Class III 56 Class IV
QoL and prognosis of dysphagic patients with PD	35	< 50 pts = 13 50–199 pts = 13 200–500 pts = 5  > 500 pts = 4	20	15	4 Class I 8 Class II 8 Class III 15 Class IV

Studies were classified according to various descriptors, including topic domain, sample size, design, presence of diagnostic criteria of the syndrome and level of evidence 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)