Table 34: The Methods and Quality of Studies Included in the Assessment of Clinical Effectiveness.

Study		Random assignment	Proper sampling	Sample size	Objective outcomes	Blind assessment	Eligibility criteria	Attrition reported	Comparable groups	Generalizable results
Surgery vs nonsurgical interventions
	Andersen et al (1988)18,19	NR	✓	✓	✓	×	✓	✓	✓	✓
	Danish Obesity Project20-22	NR	NR	NR	✓	NR	✓	✓	Sub	✓
	Swedish obese subjects23-31	×	×	NR	✓	n/a	✓	✓	×	✓
Comparison of different surgical procedures
Gastric bypass vs gastroplasty
	Hall et al (1990)53	✓	✓	✓	✓	NR	✓	✓	✓	✓
	Howard et al (1995)23	NR	NR	NR	✓	NR	✓	✓	✓	✓
	Laws et al (1981)46	✓	✓	NR	✓	NR	Sub	×	Sub	✓
	Lechner et al (1981)34	NR	NR	NR	✓	NR	✓	×	✓	✓
	MacLean et al (1995)35,36	NR	NR	NR	✓	NR	×	✓	✓	✓
	Naslund et al (1988)47-52	✓	✓	NR	✓	NR	✓	✓	✓	✓
	Pories et al (1982)41	✓	NR	NR	✓	✓	Sub	✓	✓	✓
	Sugerman et al (1987)40	✓	NR	NR	✓	NR	✓	✓	✓	✓
Gastric bypass vs jejunoileostomy
	Buckwater et al (1980)39,43,44	✓	NR	NR	✓	NR	✓	×	✓	✓
	Griffen et al (1977)32	Sub	NR	NR	✓	NR	✓	×	✓	✓
Vertical banded gastroplasty vs horizontal gastroplasty
	Andersen et al (1987)45	✓	✓	NR	✓	NR	Sub	×	Sub	Uncertain
Vertical banded gastroplasty vs adjustable gastric banding
	Nilsell et al (2001)38	✓	NR	NR	✓	×	✓	✓	✓	✓
Open vs laporoscopic gastric bypass
	Nguyen et al (2001)34	✓	✓	✓	✓	×	✓	✓	✓	✓
	Westling et al (2001)37	✓	Sub	NR	✓	Sub	✓	✓	×	✓
Open vs laparoscopic adjustable silicone gastric banding
	De Wit et al (1999)42	✓	NR	✓	✓	NR	✓	✓	✓	✓

✓ = yes; × = no; NR = not reported; sub = substandard or incomplete.

(Table reproduced with kind permission from the National Coordinating Centre for Health Technology Assessment: Clegg A, Colquitt J, Sidhu M, Royle P, Walker A. Clinical and cost effectiveness of surgery for morbid obesity: a systematic review and economic evaluation. Health Technol Assess 2002; 6(12).