Table 1.

NIH scale quality assessment for retrospective studies

Studies	Was the study question or objective clearly stated?	Was the study population clearly and fully described, including a case definition?	Were the cases consecutive?	Were the subjects comparable?	Was the intervention clearly described?	Were the outcome measures clearly defined, valid, reliable and implemented consistently across all study participants?	Was the length of follow-up adequate?	Were the statistical methods well-described?	Were the results well-described?	Quality summary
Sevas Comlek, 2020 [12]	✔	✔	✔	✔	✔	✔	✗	✗	✔	2
Xiaoxu Lu, 2022 [13]	✔	✔	✔	✔	✔	✔	✗	✗	✔	2

Quality was rated as 0 for poor (0–3 out of 9 questions), 1 for fair (4–6 out of 9 questions) or 2 for good (7–9 out of 9 questions); NA not applicable and NR not reported [11]