Table 2.

Risk of bias assessment using the National Institutes of Health quality assessment tool for case series studies.

Study	Author, year	Criteria
		1. Was the study question or objective clearly stated?	2. Was the study population clearly and fully described, including a case definition?	3. Were the cases consecutive?	4. Were the subjects comparable?	5. Was the intervention clearly described?	6. Were the outcome measures clearly defined, valid, reliable, and implemented consistently across all study participants?	7. Was the length of follow-up adequate?	8. Were the statistical methods well-described?	9. Were the results well-described?	Overall rating (good, fair, poor)
1	Frithz, 1979 [13]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Good
2	Sheppard et al, 1986 [14]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Good
3	Srinivasa N et al, 1994 [15]	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes	Good
4	Räsänen et al, 1997 [16]	Yes	Yes	No	Yes	Yes	Yes	No	Yes	Yes	Fair
5	Zanol et al, 1998 [17]	Yes	Yes	—a	Yes	Yes	Yes	Yes	—	Yes	Fair
6	Bhatia et al, 2000 [18]	Yes	Yes	Yes	Yes	Yes	Yes	—	Yes	Yes	Good
7	Zomer et al, 2002 [19]	Yes	Yes	Yes	Yes	Yes	Yes	—	Yes	Yes	Good
8	Nicolato et al, 2006 [20]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Good
9	Ahmad and Ramsay, 2009 [21]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Good
10	Kenchaia H et al, 2009 [22]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Good
11	Coşar et al, 2012 [23]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Good
12	Bhatia et al, 2013 [24]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Good
13	Mohandas et al, 2017 [25]	Yes	Yes	Yes	Yes	Yes	Yes	—	Yes	Yes	Good
14	Çınar et al, 2019 [26]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Good
15	Jerrom et al, 2019 [27]	Yes	Yes	Yes	Yes	Yes	Yes	—	Yes	Yes	Good

^aEm dashes indicate “not applicable.”