Table 4.

Newcastle-Ottawa scale quality evaluation

First author, year	Selection	Comparability	Outcome	Total
CKD and frailty associated with outcome
Wilhelm-Leen [14]	3	2	0	5
Roshanravan [15]	2	2	1	5
CKD and frailty associated
Odden [17]	3	2	0	5
Shlipak [18]	3	2	0	5
Fried [4]	4	2	1	7
Bowling [19]	4	1	1	6
Lattanzio [16]	3	2	0	5

Newcastle-Ottawa Scale Quality Criteria can be found in Additional file 1: Appendix 2.