Table 5

Quality assessment for studies

Newcastle-Ottawa Quality Assessment Scale for cohort studies18
StudyType of studySelectionComparabilityOutcome
Representativeness of the exposed cohortSelection of the non-exposed cohortAscertainment of exposure/risk factor, that is, severe versus non-severeDemonstration that outcome of interest was not present at start of studyComparability of cohorts on the basis of the design or analysisAssessment of outcomeWas follow-up long enough for outcomes to occur?Adequacy of follow-up of cohortsTotal score (out of 8 stars)
Huang et al 11 Prospective cohort***0 (No)****7 stars
Zhang et al 8 Retrospective cohort study***0 (No)**Follow-up period not mentionedUnable to assess5 stars
Wang et al 9 Retrospective cohort study**** (Yes)****8 stars
Pan et al 14 Descriptive cross-sectional study with a prospective cohort component**** (Yes)****8 stars
Guan et al 22 Retrospective cohort study**** (Yes)****8 stars
  • *Indicates one star.