Table 3.

Quality of studies

RCT Studies	Explanation of calculation of sample size	Description of mechanism for patient selection	Explanation of the causes for withdrawal of patients	Statistical analysis adequate to the type of data	Description of the control for confusing factors	Blindness for the evaluation of results	Use of p values or confidence intervals	Evaluation of quality
Nelson 1993 [22]	yes	yes	Yes	yes	yes	no	Yes	High
Tulloch 1997 [23]	yes	yes	No	yes	yes	no	yes	Medium
Illing 1998 [24]	no	yes	Yes	yes	yes	no	yes	medium
O Brien 2003 [19]	yes	yes	Yes	yes	yes	no	yes	high
Martina 2013 [7]	yes	yes	Yes	yes	yes	no	yes	high

RCT Randomized clinical trial