Author, year and country of study [reference] Jaffe et al 1988,  Israel [40] Tirosh et al 1991, Israel [41] Davidovitch et al 1994, Israel [42] Englebert et al, Netherlands [43] Kirby et al 2005, United Kingdom [27] Study, design type A A B C C Quality of individual research reports based on answers to the following  (Y = Yes; N = No)           Inclusion exclusion criteria well defined and adhered to Y Y N Y Y No serious questions of bias Y Y Y N N Statistically significant and clinically important effect Y Y N N N Results generalizable to other populations Y Y N/Y Y N/Y Characteristics of a well-designed study clearly addressed Y Y N N Y Overall quality of study + + Ø Ø Ø Conclusion Grade (Level)  I  I III III III Study Design type: A = randomised, controlled trial; B = Cohort study; C = nonrandomized trial with concurrent or historical controls, case-control study, diagnostic test with sensitivity and specificity, population-based descriptive study; D = cross-sectional study, case series, case report Quality of study: If a study has 2 or more YES it may be designated a (+); If a study has 2 or more NO it may be designated a (-); If answers pertaining to (+) or (-) do not indicate the report is exceptionally strong or weak then the report will be graded as neutral Ø Conclusion grades: Level I – level III and Grade not assignable. Conclusion supported by: Good evidence (Level I); Fair evidence (Level II); Limited evidence (Level III). Grade not assignable where there is no evidence to support or refute conclusion

Table 1: Results of primary research report quality categories employing an evidence grading system [39].