Table 2.

Risk of bias using QUIPS tool.

Study (PMID)	Study participation (max. 15)	Study attrition (max. 15)	Prognostic factor measurement (max. 15)	Outcome measurement (max. 15)	Statistical analysis and reporting (max. 15)	Quality score (max. 75)
32217556	15	12.5	12.5	15	15	70
32217650	15	12.5	15	15	15	72.5
32269088	15	12.5	12.5	15	15	70
32188484	15	10	12.5	15	15	67.5
32294485	15	12.5	15	15	15	72.5
32304745	15	10	12.5	15	15	67.5
31986264	15	10	12.5	15	15	67.5
32031570	15	10	12.5	15	15	67.5
32105632	15	10	12.5	15	15	67.5
32109013	15	10	12.5	15	15	67.5
32167524	15	10	12.5	15	15	67.5
32171076	15	12.5	12.5	15	15	70
32191764	15	10	10	15	12.5	62.5
32173725	15	12.5	12.5	15	15	70
32176772	15	10	12.5	15	15	67.5
32409504	15	10	12.5	15	15	67.5
32564693	15	12.5	10	15	15	67.5

QUIPS: quality in prognosis studies; the quality of the studies was ranked high if ≥60 points (≥80% of the maximum score); moderate if 45–59 points (≥60% and <80% of the maximum score); and low if <45 points (<60% of maximum score).