Table 4. Quality assessment of included studies.
| Authors | Randomisation | Allocation concealment | Random sequence generation | Blinding | Reporing of withdrawals | Jaded score |
| Paolisso 1993 | Y | U | U | Y | Y | 3 |
| Reaven 1995 | Y | U | U | Y | Y | 3 |
| Tutuncu 1998 | Y | U | U | Y | U | 2 |
| Gazis 1999 | Y | U | U | Y | Y | 3 |
| Paolisso 2000 | Y | U | U | Y | Y | 3 |
| Manzella 2001 | Y | U | U | Y | U | 2 |
| Park 2002 | Y | U | U | Y | Y | 3 |
| Chen 2004 | Y | U | Y | U | Y | 3 |
| Economides 2005 | Y | U | U | Y | Y | 3 |
| Ble-Castillo 2005 | Y | U | U | Y | Y | 3 |
| Baliarsingh 2005 | Y | U | U | Y | Y | 3 |
| Boshtam 2005 | Y | U | U | Y | U | 2 |
| Ward 2007 | Y | U | Y | Y | Y | 4 |
| Oliveira 2011 | Y | U | U | Y | U | 2 |
Y, yes; U, unclear; Randomisation:the study described as randomized; Random sequence generation: the correct method for generation of random numbers computer random numbers table, shuffled cards or tossed coins, and minimization; Allocation concealment: Adequate concealment was that up to the point of treatment (eg, central randomisation); Double-blinding: masking to both researchers and patients; Reporting of withdrawals: The numbers and reasons for withdrawal in each group had to be stated for a point to be awarded.