Table 2.

Quality of individual non-randomized controlled trial methodology.

Study	Selection a				Comparability b		Exposure c			Newcastle–Ottawa Scale Score
	1	2	3	4	5A	5B	6	7	8
Elsayed (2020) [10]	Yes	No	Yes	Yes	No	No	Yes	Yes	Yes	6
Yılmaz (2021) [12]	Yes	No	No	Yes	Yes	Yes	Yes	Yes	Yes	7
Efe Atila (2022) [13]	Yes	No	Yes	Yes	No	No	Yes	Yes	Yes	6
Schumacher (2023) [14]	Yes	Yes	Yes	Yes	No	No	Yes	Yes	Yes	7

A star rating system was used to indicate the quality of a study, with a maximum rating of nine stars. A study could be awarded a maximum of one star for each numbered item within the selection and exposure categories. ^a: Selection (4 items): adequacy of case definition; representativeness of cases; selection of controls; and definition of controls. ^b: Comparability (1 item): comparability of cases and controls on the basis of design or analysis. ^c: Exposure (3 items): ascertainment of exposure; same method of ascertainment used for cases and controls; and non-response rate (same rate for both groups).