Table 2.
Risk of bias assessment
| Study, year | Randomization process | Intended interventions | Missing outcome data | Measurement of the outcome |
Selection of the reported result | Overall result | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Bulilete et al., 2019 [108] | Some concern | No statement for allocation concealment | Low risk | Both blinded | Low risk | 1/98 dropped, unrelated to the outcome | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Lee et al., 2016 [104] | Some concern | No statement for allocation concealment | Some concern | No specific information | Some concern | No specific information | Some concern | No specific information | Low risk | Predefined outcomes | Some concern |
| Stepanović et al., 2015 [103] | Some concern | No statement for allocation concealment | Some concern | Blinded only in assesor | Some concern | No specific information | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Makharita et al., 2015 [102] | Some concern | No statement for allocation concealment | Low risk | Both blinded | Low risk | No exclusion | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Makharita et al., 2012 [101] | Some concern | No statement for allocation concealment | Low risk | Both blinded | Low risk | 3/64 dropped, unrelated to the outcome | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Krcevski Skvarc and Kamenik, 2010 [98] | High risk | No specific information | Some concern | No specific information | Low risk | No exclusion | Some concern | No specific information | Low risk | Predefined outcomes | High risk |
| Ji et al., 2009 [97] | Some concern | No statement for allocation concealment | Some concern | Blinded only in assesor | Low risk | 19/132 dropped, propotions existed | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| van Wijck et al., 2006 [96] | Some concern | No statement for allocation concealment | Some concern | Blinded only in assesor | Low risk | 33/598 dropped, propotions existed | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Pasqualucci et al., 2000 [110] | Some concern | No statement for allocation concealment | Some concern | Blinded only in assesor | Low risk | 31/600 dropped, protocol violation | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Ahmed et al., 1998 [94] | Some concern | No statement for allocation concealment | Some concern | Blinded only in assesor | Low risk | No exclusion | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Bowsher, 1997 [93] | Low risk | Sealed envelop | Low risk | Both blinded | Low risk | 6/80 dropped, unrelated to the outcome | Low risk | Blinded | Low risk | Predefined outcomes | Low risk |
| Harding and Porter, 1991 [114] | High risk | No statement for allocation concealment, randomization sequence | Some concern | Both blinded | Some concern | 8/46 dropped, no specific propotion revealed | Low risk | Blinded | Low risk | Predefined outcomes | High risk |
| Benoldi et al., 1991 [92] | High risk | No statement for allocation concealment, randomization sequence | Some concern | Different procedure | Low risk | 1/36 dropped, unrelated to the outcome | Some concern | No specific information | Low risk | Predefined outcomes | High risk |
| Esmann et al., 1987 [88] | High risk | No statement for allocation concealment, randomization sequence | Some concern | Both blinded | Low risk | No exclusion | Low risk | Blinded | Low risk | Predefined outcomes | High risk |
| Cobo et al., 1986 [87] | High risk | No statement for allocation concealment, randomization sequence, basement difference existed | Low risk | Both blinded | Low risk | No exclusion | Low risk | Blinded | Low risk | Predefined outcomes | High risk |
| Balfour et al., 1983 [85] | Some concern | No statement for allocation concealment, randomization sequence | Low risk | Both blinded | Low risk | No exclusion | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Esmann et al., 1982 [84] | Some concern | No statement for allocation concealment, randomization sequence | Low risk | Both blinded | Low risk | 1/56 dropped | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Bean et al., 1982 [83] | High risk | No statement for allocation concealment | Some concern | Both blinded | Some concern | 2/31 dropped | Low risk | Blinded | Low risk | Predefined outcomes | High risk |
| Keczkes and Basheer, 1980 [115] | Some concern | No statement for allocation concealment, randomization sequence | Low risk | Both blinded | Low risk | No exclusion | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Cui et al., 2018 [107] | Some concern | No statement for allocation concealment | Low risk | Both blinded | Low risk | 5/102 dropped, unrelated to the outcome | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Cui et al., 2017 [105] | Some concern | No statement for allocation concealment, randomization sequence | Some concern | Both blinded | Low risk | 2/96 dropped | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Ni et al., 2017 [106] | Some concern | No statement for allocation concealment | Some concern | No specific information | Low risk | 5/100 dropped, unrelated to the outcome | Some concern | No specific information | Low risk | Predefined outcomes | Some concern |
| Zheng et al., 2019 [109] | Some concern | No statement for allocation concealment | Low risk | Both blinded | Low risk | 13/153 dropped | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Hwang et al., 1999 [79] | High risk | No statement for allocation concealment, randomization sequence | Some concern | No specific information | Low risk | No exclusion | Some concern | No specific information | Low risk | Predefined outcomes | High risk |
| Wan et al., 2019 [120] | Some concern | No statement for allocation concealment | Some concern | Both blinded | Low risk | 2/96 dropped, unrelated to the outcome | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Hügler et al., 2002 [116] | High risk | No statement for allocation concealment, randomization sequence | Some concern | Both blinded | Low risk | No exclusion | Low risk | Blinded | Low risk | Predefined outcomes | High risk |
| Cui et al., 2016 [117] | Some concern | No statement for allocation concealment, randomization sequence | Some concern | No specific information | Low risk | No exclusion | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Payne et al., 1989 [91] | Some concern | No statement for allocation concealment | Low risk | Both blinded | Low risk | 3/41 dropped | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Wood et al., 1994 [111] | Some concern | No statement for allocation concealment | Low risk | Both blinded | Low risk | 51/400 dropped, unrelated to the outcome | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| McGill et al., 1983 [86] | Some concern | No statement for allocation concealment | Low risk | Both blinded | Low risk | 3/40 dropped, unrelated to the outcome | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Wassilew et al., 1987 [89] | Some concern | No statement for allocation concealment, randomization sequence | Low risk | Both blinded | Low risk | 2/60 dropped | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Mandal et al., 1988 [90] | High risk | No statement for allocation concealment, randomization sequence, basement difference existed | Low risk | Both blinded | Low risk | 8/64 dropped, unrelated to the outcome | Low risk | Blinded | Low risk | Predefined outcomes | High risk |
| Lee et al., 1999 [95] | High risk | No statement for allocation concealment, randomization sequence, basement difference existed | Some concern | No specific information | Low risk | No exclusion | Low risk | Blinded | Low risk | Predefined outcomes | High risk |
| Harding et al., 1986 [119] | Some concern | No statement for allocation concealment | Some concern | No specific information | Some concern | No specific information | Some concern | No specific information | Low risk | Predefined outcomes | Some concern |
| Kanodia and Singhal, 2011 [99] | Some concern | No statement for allocation concealment, randomization sequence | Low risk | Both blinded | Some concern | No specific information | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Kanodia et al., 2012 [100] | Some concern | No statement for allocation concealment, randomization sequence | Low risk | Both blinded | Some concern | No specific information | Low risk | Blinded | Low risk | Predefined outcomes | Some concern |
| Manabe et al., 2004 [118] | High risk | No statement for allocation concealment, randomization sequence, basement difference existed | Low risk | Both blinded | Low risk | 3/59 dropped, unrelated to the outcome | Low risk | Blinded | Low risk | Predefined outcomes | High risk |
| Clemmensen and Andersen, 1984 [112] | High risk | No statement for allocation concealment, randomization sequence, basement difference existed | Low risk | Both blinded | Low risk | 5/60 dropped, unrelated to outcome | Low risk | Blinded | Low risk | Predefined outcomes | High risk |
| Eaglstein et al., 1970 [113] | High risk | No statement for allocation concealment, randomization sequence | Low risk | Both blinded | Some concern | 1/35 dropped | Low risk | Blinded | Low risk | Predefined outcomes | High risk |