Table 5.

Evaluation of study quality according to Newcastle-Ottawa Scale

Author/Year	Selection 1 2 3 4				Comparability 5	Outcomes 6 7 8			Total score
Sai et al., 201619	*	*	*	-	**	*	*	*	8
Bansal et al., 201615	*	*	*	-	**	*	*	*	8
Abid et al., 20167	*	*	*	-	*	*	*	*	7
Woitas et al., 201318	*	*	*	-	**	*	*	*	8
Dupont et al., 20128	*	*	*	-	*	*	*	*	7
Gao et al., 201121	*	*	-	-	**	*	*	*	7
Keller et al., 200917	*	*	*	-	**	*	*	*	8
Gao et al., 200922	*	*	-	-	*	*	-	*	5
Alehagen et al., 200920	*	*	*	-	*	*	*	*	7
Acuna et al., 200916	*	*	*	-	*	*	*	*	7
Koenig et al., 200724	*	*	-	*	*	*	*	*	7
Ix et al., 200723	*	*	*	-	**	*	*	*	9

1 - Representativeness of the exposed cohort: all the studies received one star, because the exposed cohort was a little representative of the average in the community; 2 - Selection of the unexposed cohort: all studies received one star, because the unexposed cohort was obtained in the same community of the exposed cohort; 3- Determination of exposure: only studies that dosed cystatin C using the immunonephelometry or immunoturbidimetry methods received a star; 4 - Demonstration that the outcome of interest was not present at the beginning of the study: studies in which patients did not present any cardiovascular disease at the beginning of the study received one star; 5 - Cohort comparability based on design and analysis: studies that performed multivariate regression analysis of Cox proportional hazards and defined normal renal function as GFR > 60 mL/min/1.73 m² received 2 stars. Studies that only defined normal renal function as GFR > 60 mL/min/1.73 m² but did not perform multivariate regression analysis of Cox proportional hazards received 1 star. 6 - Determination of outcome: all studies received one star, because the evaluation of the outcome was performed by the physicians independently; 7 - Adequate follow-up period for the occurrence of outcome (s): studies in which patients were followed for at least six months received one star, and studies in which patients were followed for less than six months did not receive a star; 8 - Adequacy of the follow-up period of the cohort: studies in which at least 90% of the patients were followed to the end or who did not comment if there were significant loss of patients during follow-up received one star.