Validity of random-digit-dialing in recruiting controls in a case-control study.
OBJECTIVE
To evaluate whether the participating controls represented the underlying population in a colorectal cancer case-control study in a geographically isolated North American population.


METHODS
The characteristics of the study controls recruited through Random-digit-dialing (RDD) were compared with those in the corresponding target population estimates.


RESULTS
Participating controls were more likely to have higher levels of education and income and were less likely to be smokers.


CONCLUSIONS
Study controls recruited through RDD tend to have higher socioeconomic status, which may lead to overestimation of a number of risk factors in this study.
Wang
Peizhong Peter
PP
Division of Community Health and Humanities, Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada. pwang@mun.ca
Dicks
Elizabeth
E
Gong
Xianying
X
Buehler
Sharon
S
Zhao
Jinhui
J
Squires
Josh
J
Younghusband
Banfield
B
McLaughlin
John R
JR
Parfrey
Patrick S
PS
D000328:Adult; D000368:Aged; D015982:Bias; D016022:Case-Control Studies; D004522:Educational Status; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009523:Newfoundland and Labrador; D018579:Patient Selection; D012307:Risk Factors; D012907:Smoking; D012923:Social Class; D013689:Telephone