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. 2019 Dec 23;26(1):104–118. doi: 10.1093/humupd/dmz036

Table I. Internal validity of included studies using the NOS for assessing the quality of observational studiesa.

Study Selection Comparability
of cases and controls		 Exposure Total risk of bias
(number of stars)
Adequate
case
definition?		 Representative cases? Selection
of controls		 Definition
of controls		 Ascertainment
of exposure?		 Similar method
of ascertainment
in both
groups		 Non-response
rate
Crisosto et al. 2007 * * NR * * * * * NR 7
Sir-Petermann et al. 2007 * * NR * * * * NR 6
Recabarren et al. 2008 * * NR * * * * * NR 7
Maliqueo 2009 * * NR * - * * NR 5
Sir-Petermann et al. 2009 * - NR * * * * NR 5
Kent et al. 2008 * - * * * * * NR 6
Legro et al. 2017 * NR NR * * * * * NR 6
Crisosto et al. 2017 * * NR * * * * NR 6
De Wilde et al. 2018 * - * * * * * - * 7

- = study did not receive a star for this item, * = study receives a star for this item, total risk of bias: 1–3 stars = high, 4–6 stars = medium, 7–9 stars = low; NR = not reported.