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Table 3 Newcastle-Ottawa quality assessment scale for before-after observational studies.

From: Routine chest x-rays in intensive care units: a systematic review and meta-analysis

  Representativeness of the exposed cohort Selection of the non-exposed cohort Ascertainment of exposure Outcome of interest not present at the start of study Cohorts comparable on the basis of design or analysis Assessment of outcome Adequacy of duration of follow-up Adequacy of completeness of follow-up
Rao et al., 1997 [17]   * * * *    
Price et al., 1999 [18] * * * * *   *  
Leong et al., 2000 [19]   * * * *   *  
Krinsley et al., 2003 [20] * * * * *   *  
Graat et al., 2007 [21] * * * * *    
Hendrikse et al., 2007 [22] * * * * * *   
  1. Refer to reference [9] for a description of Newcastle-Ottawa Quality Assessment Scale for cohort studies. In general, more stars denote higher quality. A study can be awarded a maximum of one star for each item within the 'Selection' and 'Outcome' categories. aA maximum of four stars can be given for 'Selection'. 'Representativeness' is awarded a star if the cohort is truly or somewhat representative of the population of interest. For selection of the non-exposed cohort, a star is awarded if it is drawn from the same population as the exposed cohort. Exposure is satisfactorily ascertained if data are collected from a secure record. bA maximum of two stars can be given for 'Comparability', one each for controlling of two important confounders in either the design or analysis phase. cA maximum of three stars can be given for 'Outcome'. 'Assessment of outcome' is awarded a star if the outcomes were assessed by independent blind assessment or record linkage. The duration of follow-up was considered adequate if it was long enough for the outcomes to occur. Completeness of follow-up was considered adequate if all patients were accounted for or if the number lost to follow-up was sufficiently low to be unlikely to introduce bias.