Table 3 Information on the collection of samples of the studies included in the meta-analysis

(Croitoru et al, 2004)

Prospective series

Regional Canadian

Age and sex matched

Same region of Canada

(Farrington et al, 2005) and replication

Prospective series

Scottish population

Age, sex and region matched

Scottish population

(Peterlongo et al, 2005)

Consecutive series

Regional USA

Chosen from 17 000 cohort study as cancer free and age matched

Same region USA and ethnically matched.

(Fleischmann et al, 2004)

Unrelated retrospective series

Three regions of UK

Spouses of individuals from another cancer study

No information

(Kambara et al, 2004)

Sporadic series

Regional Australia

Healthy blood donors

Same region of Australia

(Wang et al, 2004)

No information

Regional USA

Individuals negative by colonoscopy

Same region of USA

(Enholm et al, 2003)

Systematic series

Finnish population

Healthy blood donors

No information

(Zhou et al, 2005)

Sporadic series

Three regions of Sweden

Healthy blood donors

Stockholm region