A national audit: clinical validation and root cause analysis of true Scottish PCC-3 rate from 2012 to 2015

Introduction Colonoscopy is the gold standard investigation for diagnosis, surveillance and screening of colorectal cancer (CRC).1 2 Not all CRC is detected or prevented following a colonoscopy and the 3 year post colonoscopy cancer rate (PCC-3) in NHS England has been reported as 7.4%.3 The 2012–2015 Scottish PCC-3 rate is 8% using linkage analysis from the Scottish Cancer Registry. The aim of this audit was to clinically validate PCC-3 cases between 2012–2015 to ascertain their accuracy and to subcategorise cases using methodology proposed by the World Endoscopy Organisation (WEO).4

Method Colonoscopies performed by individual health boards between 2012–2015 were determined by clinical leads and Public Health Scotland. Linkage to the Scottish Cancer Registry identified cases of CRC. PCC-3 cases were defined as having had a CRC diagnosis 6–36 months after a colonoscopy and these were returned to boards with standardised information. Cases were examined to determine if true PCC-3. Demographics, referral stream, quality of index endoscopy, mode of diagnoses and cancer site were noted for each case.

Results 739 cases were analysed. Of the confirmed 652 PCC-3 cases, 37.9% died from CRC. 56 cases were from high risk groups; 6.9% had IBD and 1.7% had a genetic syndrome. Regarding cancer site, 24.8% were rectal, 22.7% caecal and 20.6% ascending colon. Rates for caecal intubation, caecal photography, rectal retroflexion and rectal photography were 89%, 23.3%, 41.6% and 9.4% respectively. PCC-3 cases were categorised by WEO classification as below.4

Conclusions This is the largest reported series of PCC-3 cases determined by registry linkage and yields valuable information for services on the aetiology of these cases. The most common category is Type B. This emphasises the importance of on-going quality improvement measures. With improved awareness, advancing technology, standardisation of training and upskilling of the workforce supported by the National Endoscopy Academy, we hope that future PCC-3 rates will fall.