Differences in diagnostic activity in general practice and findings for individuals invited to the danish screening programme for colorectal cancer: a population-based cohort study

Abstract

Objective: To investigate the diagnostic activity in general practice and the cumulative incidence of colorectal cancer (CRC) in individuals invited to the Danish national screening programme for CRC.

Design: A historical population-based cohort study.

Setting: The Danish CRC screening programme and general practice.

Subjects: The 376,198 individuals invited to the Danish CRC screening programme from 1 March to 31 December 2014.

Main outcome measures: The diagnostic activity (consultations and haemoglobin measures) in general practice in the year preceding the screening invitation and the cumulated incidence of CRC in the year following the screening invitation.

Results: Screening participants had significantly higher diagnostic activity than non-participants. Individuals with a positive faecal immunochemical test (FIT) had higher diagnostic activity compared to individuals with a negative FIT, and a small increase in the months leading up to the invitation. Individuals with a screen-detected CRC had lower diagnostic activity than individuals with no CRC. In total, 308 (25.3%) of CRCs diagnosed in the invited population were diagnosed outside the screening programme. Non-participants with CRC more often had low socio-economic status, high comorbidity and stage IV CRC than participants with CRC.

Conclusions: There was a tendency that participants and those with a positive FIT had a higher diagnostic activity the year before the screening. This was not seen for those with CRC detected through screening. CRC must still be diagnosed in general practice in the invited population and non-participants are of special interest as they have higher risk of late stage CRC. Key Points Current awareness:Individuals with colorectal cancer (CRC) in screening may be symptomatic and CRC may still occur outside screening in the invited population. Most important points:The majority of individuals with CRC in screening cannot be expected to be diagnosed on symptomatic presentation in general practice GPs have to be aware that CRC still occurs outside screening in the invited population Non-participants with CRC are often deprived and have late stage CRC.

Keywords: Cohort study; Denmark; colorectal neoplasm; general practice; mass screening.

Figure 1.

Flowchart of the study population. The number of CRC diagnoses for each subgroup is stated for the year following the screening invitation.

Figure 2.

(A-C) Mean rates of daytime face-to-face consultations and haemoglobin measurements for subgroups in the screening for CRC. Estimates are for 3-month intervals, 12 months preceding invitation to screening. The upper graph illustrates the unadjusted average consultation rate for individuals in subgroups. The lower graph illustrates the IRRs for comparison of subgroups adjusted for age, gender, country of origin, educational level, labour market affiliation, marital status, CCI score, prescriptions of medicine against haemorrhoids, NSAIDs, acetylsalicylic acids and anticoagulant drugs.

Figure 3.

Cumulative incidence of CRC among individuals invited for screening participation, one year following invitation. Incidence was stratified for screening participation. In total, 907 CRCs were diagnosed in the screening (red curve) and 308 CRCs were diagnosed outside the screening (blue and green curves).