Allocation
All 44 included studies were stated to be randomised, but only
seven provided descriptions of themethods used to generate the sequence
(Standard - Both 1996; Standard -Unclear 1996; Standard
- Both 2008b; Standard -Group 2006; Standard - Individual 03b;
Standard - Individual 03c; Unclear - Both 2007). Only Standard -
Both 1996 describedmethod of concealment.Most studies, therefore,
are classified as of ’unclear’ quality with a moderate risk of
selection bias and of overestimate of positive effect.
Blinding
Seven studies were stated to have used single (assessor) blinding
(Brief - Group 1999; Standard - Both 1996; Standard - Group
1988; Standard - Group 2006; Brief - Group 2007; Standard -
Individual 93; Standard - Unclear 1996). One trial was double
blind (Standard - Individual 03c) and one open label (Brief -
Individual 1996). Of those studies that were blinded in some way,
most did not describe the blinding methods used, and none tested
the success of blinding for participants or assessors. The remaining
studies did not report whether blinding had been used. We
therefore had to rate the risk of observer bias as (at best) ’unclear’.
This gathers further potential for overestimate of positive effects
and underestimate of negative ones.
Incomplete outcome data
Most studies used Intention-to-treat (ITT) method of analysis,
except for eight which did not include any data from those who
left early (Unclear - Both 2007; Unclear - Individual 2008; Brief
- Unclear 2005; Standard - Both 2004; Standard - Individual
03c; Standard - Both 2008b; Standard - Group 2006; Standard -
Individual 03b).
Selective