Bisphosphonate use and gastrointestinal tract cancer risk: Meta-analysis of observational studies

Table 4 Assessment of study quality

Study		Quality assessment items
Representativeness	Ascertainment of exposure: Secure record or structured interview	Demonstration that outcome of interest		Assessment of outcome: Independent blind assessment or record linkage was not present at start of study	Study controls for age, cigarette smoking, BMI status
Cohort studies
Steinbuch et al[9]	- (female)	+	+	+	- (randomized controlled trials)
Abrahamsen et al[10]	+	+	-	+	+ (age)
Solomon et al[11]	- (medicare beneficiaries)	+	-	+	- (not reported)
Cardwell et al[7]	+	+	+	+	+++ (age, cigarette smoking, BMI)
Case-control studies
Green et al[8]	+	+	-	+	+++ (age, cigarette smoking, BMI)
Nguyen et al[12]	- (Barrett’s esophagus)	+	+	+	+ (age)
Rennert et al[13]	- (female)	+	+	+	++ (age, BMI)

BMI: Body mass index.