Table 1.

Modified Newcastle-Ottawa Scale criteria

Adapted Newcastle-Ottawa Scale Items	High-quality items carrying a low risk of bias (green)	Low-quality items carrying a high (red) or an unknown (yellow) risk of bias
Item 1: Representativeness of the initial study population - patients with GI bleeding and CKD/ESRD	All patients with upper or lower GI bleeding and CKD/ESRD were included.	Low: any selection criteria were applied to the study population (e.g., only transplanted patients).
		Unknown: no data on selection process.
Item 2: Representativeness of the initial study population - patients with GI bleeding without CKD/ESRD	All patients with upper or lower GI bleeding without CKD/ESRD included.	Low: any selection criteria were applied to the study population.
		Unknown: no data on selection process.
Item 3: Ascertainment of exposure	We defined chronic renal failure as present when eGFR was < 60 mL/min at least 3 mo. We defined end-stage renal disease as a condition where hemodialysis or chronic peritoneal dialysis is performed at least for 3 mo.	Low: CKD or ESRD is not present in all of the patients.
		Unknown: no definitions of the conditions mentioned are provided.
Item 4: Comparability of cohorts A	Study controls for age: no significant difference was detected.	Low: significant difference was detected.
		Unknown: no statement.
Item 5: Comparability of cohorts B	Study controls for taking ulcerogenic drugs: no significant difference was detected	Low: significant difference was detected between taking ulcerogenic drugs.
		Unknown: no comparison made by taking ulcerogenic drugs.
Item 6: Follow-up time for rebleeding	The follow-up time is clearly defined.	Low: incomplete follow-up
		Unknown: no follow-up time is mentioned.

CKD: Chronic kidney disease; ESRD: End-stage renal disease.