Summary of results:

The screening methods gFOBT and FIT are non-invasive procedures that are therefore not likely to cause any direct harm to the participants. Harms can be observed on a psychological basis or can be due to subsequent colonoscopy examination, with different timing.

Summary table of selected references

Results from different trials:1) Physical reactions to colonoscopy

Risks of severe complications such as gut perforation and hemorrhage can be immediate or delayed (7-21 days after colonoscopy). {1}

One study specifically examined the risk of immediate and late reactions other than gut perforation and hemorrhage after colonoscopy and sigmoidoscopy in a screening setting {5}.

Among immediate reactions, patients reported serious reactions following bowel preparation (mainly abdominal pain, bowel distension and anal irritation), severe pain immediately after the exam and embarrassment. {5}

The most common post-procedural complaints were abdominal distension and pain.

2) Psychological impact

Psychological impact can be observed as well during the whole period of testing, including time before testing and time after obtaining the results. In a clinical trial (Parker et al, 2002) a general health questionnaire was sent to 2184 subjects before the offer of screening, and 1541 (70.6%) were returned. Of the 1693 subjects offered the questionnaire 3 months after the offer of screening, 1303 (77%) returned it. Anxiety scores were measured in 100 test positive patients and were highest after notification of a positive test and before investigation by colonoscopy. In patients with false positive results, scores fell the day after colonoscopy and remained low 1 month later. No sustained anxiety has been seen in screening participants.