Uptake (participation) rate

The number of people who have been screened, within a defined time frame following an invitation, as a proportion of all people who are invited to attend for screening.

The effectiveness of the programme will depend on the participation rate. In the randomised FOBT trials, uptake at the first round was between 49.5% and 66.8% (Table 3.2); uptake at subsequent rounds varied according to the policy for reinvitation. In a US study that recruited volunteers 75%–78% of subjects invited were screened at least once (Mandel et al. 1993). Reported uptake in population-based programmes ranges from 17.2% to 90.1% at the first round; the range at subsequent rounds is smaller 

N people invited and screened/tested during the time frame* 

N eligible people invited during the time frame*  

* equal to the defined screening interval or reporting period

For flexible sigmoidoscopy, uptake rates in RCTs ranged from 32.4% to 83.5%, again with high rates being associated with recruitment of volunteers or those who had expressed interest in participation). In population-based programmes, uptake rates range from 7% to 55%

Outcomes with faecal occult blood testing (FOBT) for primary screening  

FOBT indicators will vary according to the type of test used and programme policy, and therefore these should be reported.

Inadequate FOBT rate  

The rate of inadequate tests is defined as the proportion of people screened with one or more FOBT returned during the respective time frame (e.g. a 12-month period) none of which were adequate.

Rates of inadequate tests should remain low. They reflect, among other things, the understanding of the people who are using a test and therefore also the quality of the information provided to them. 

In population-based programmes, inadequate gFOBT rates between 0.4% and 4.5%  have been reported. No data are available yet for iFOBT. 

Positive FOBT rate 

In the RCTs of gFOBT, the positive rate without rehydration was 1.2%–3.8%, and with rehydration 1.7%–15.4%. In average risk populationbased programmes the positive rate for gFOBT in participants aged 50-69 years was 1.5% – 8.5% in the first round. Only two studies have reported rates at subsequent rounds, with positive rates of 0.8% and 1.8%

Positive rates should be presented in a table by 5–year age groups and gender. Positive rates are higher in men than in women and increase with age in both genders reflecting the natural history of the disease.  

Referral to follow-up colonoscopy after FOBT 

The rate of referral for follow-up colonoscopy after a positive FOBT is defined as the proportion of people screened with a positive test and referred to colonoscopy among those presenting with a positive/abnormal test during the respective time frame.