Table 2.
Assessment of risk of bias within and across included studies
| Study | Study year | NOS/ STROBE score | GRADE | Allocation concealment (Selection bias) | Blinding | Incomplete outcome data | Random sequence generation | Selective outcome reporting | Other sources of bias |
|---|---|---|---|---|---|---|---|---|---|
| Cox H | 2014 | 4/19 | VL | N | Y | Y | N | Y | A |
| Brust JC | 2012 | 4/19 | VL | N | Y | N | N | N | A, D |
| Vaghela JF | 2015 | 4/19 | VL | N | Y | Y | N | Y | A, D |
| Oyieng’o D | 2012 | 4/19 | VL | N | Y | Y | N | N | A, D |
| Joseph P | 2011 | 4/19 | VL | N | Y | Y | N | N | A, D |
| Van Deun A | 2010 | 5/20 | L | N | Y | Y | N | Y | A, D |
| Brust JC | 2010 | 5/20 | L | N | Y | Y | N | Y | A, D |
| Singla R | 2009 | 4/19 | VL | N | Y | Y | N | Y | A, D |
| Tupasi TE | 2006 | 4/19 | VL | N | Y | Y | N | Y | A, D |
| Thomas A | 2007 | 4/19 | VL | N | Y | Y | N | Y | A, D |
| Liu CH | 2011 | 5/20 | L | N | Y | Y | N | Y | A, D |
| Keshavjee S | 2008 | 5/20 | L | N | Y | Y | N | Y | A, D |
| Shin SS | 2007 | 5/19 | L | N | Y | N | N | Y | A, D |
| Cox HS | 2007 | 4/19 | VL | N | Y | N | N | N | A,D |
| Wei XL | 2015 | 4/19 | VL | N | Y | Y | N | N | A,D |
| Hirpa S | 2013 | 5/20 | L | N | Y | N | N | N | A, D |
A Attrition bias, D Detection bias
VL Very Low: We are very uncertain about the estimate
L Low: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate
H High: Further research is very unlikely to change our confidence in the estimate of effect
NOS score < 4: Low quality
NOS score 4–5: Moderate quality
Y: Low risk of bias
N: High risk of bias