PROspective Multicentre Study to Identify Diagnostic Key PERfOrmance Indicators in Upper GI Endoscopy (PROSPERO)

BACKGROUND Esophagogastroduodenoscopy (EGD) is the gold-standard test for investigating upper gastrointestinal (GI) tract pathology. The learning curve for EGD is generally steep and it is often performed by trainees at the mid stages of core training as well as nurse endoscopists. Currently the Joint Advisory Group for GI endoscopy (JAG) recommends a minimum number of 200 procedures to acquire the skills and perform endoscopy independently. However, there has been very little research done to set the standard required to measure EGD performance. The only validated quality indicators in EGD include the successful J-manoeuvre rate and D2 intubation rate, which reflect very basic skills and do not measure diagnostic ability. This contrasts with key performance indicators (KPI) for colonoscopy, for which extensive research has led to development of formal quality performance indicators. In colonoscopy formal quality indicators include (i) cecal intubation rate, (ii) adenoma detection rate, (iii) rectal retroversion rate, (iv) colonoscopy withdrawal time, (v) polyp retrieval rate, (vi) post-colonoscopy colorectal cancer rate and (vii) perforation rate. This has allowed researchers to demonstrate that poor quality colonoscopy leads to an increase in the incidence of interval cancers.

Similar benchmarks have not been set for the upper GI tract. A recent UK study revealed that 7.7% cases of upper GI cancers were missed on previous EGD and that there was a correlation between missed cancer and high number of procedures per lists and hence, arguably, those performed under user time pressure. This is in line with studies on other Western populations indicating that between 5.3% and 13.9% of patients with upper GI cancers have had normal EGD reported within the previous 3 years. Given that gastroscopy is the most commonly performed procedure in endoscopy units in the UK and its demand is increasing, there is an urge to identify diagnostic KPI to measure diagnostic skills, to improve quality of the endoscopies and to reduce the rate of missed diagnoses. Furthermore, such minimum quality standards are extremely important to counteract the potential negative effects on the performance of the pressure faced by endoscopy departments to deliver diagnostic and therapeutic procedures in a timely fashion. The importance of adequate procedure time for diagnostic accuracy has been demonstrated both in the detection of oesophageal and gastric neoplastic lesions. For detection of upper GI neoplasia, it has been demonstrated that a minimum of 7 minutes per procedure should be spent in order to ensure adequate visualisation and allow detection of high-risk lesion . In a Korean study, that compared faster with slower endoscopists, all of whom had adequate training and experience, the slower endoscopists (withdrawal time from duodenum >3min) had a significantly higher detection rate of upper GI neoplasia. Finally, in the context of Barrett's oesophagus (BO), longer inspection times during EGD correlated with increase detection rate.

Pre-malignant lesions in the upper GI tract are generally understudied when compared to those in the lower GI tract. Furthermore, their epidemiology seems to vary with geography, and this has not been inadequately investigated in the UK. Barrett's esophagus (BE) is the only known precursor to esophageal adenocarcinoma. The population prevalence is difficult to estimate given that the condition can be asymptomatic, and the diagnosis is only made by endoscopy and biopsy. It is estimated that the prevalence in the general population in Western Countries is 1-2% with significant geographic variation, but increases in patients undergoing endoscopic procedures (4.0% in Dutch population, 5.6% USA). However, the majority of studies looking at BE prevalence are confounded by the fact that most procedures were performed for GERD symptoms generating selection bias. In studies performed in patients referred for colonoscopy (n=1500 approximately) the prevalence of BE varied between 6.8% and 16.7%.

Similar to oesophageal cancer, gastric cancer has its own pre-malignant precursors including gastric intestinal metaplasia (GIM) and gastric atrophy (GA) . The endoscopic diagnosis of GA and GIM however is not straightforward as the colorimetric shift from normal to pathological mucosa is subtle and additional endoscopic signs such as disappearance of gastric folds can be affected by the degree of air insufflation. The prevalence of GA can reach up to 33.3% in Western Europeans and is higher in East Asia. For GIM, the reported population prevalence in Western Countries ranges from 7 to 28.6%. These rates are however probably affected by selection bias, such as enrichment of individuals affected by H. pylori infection. In a Dutch study on patient referred for colonoscopy 0.8% had GA, 7.1% had both GA and GIM and 1.4% had gastric dysplasia.

For esophageal squamous dysplasia, the precursor lesion of oesophageal squamous cell carcinoma, prevalence estimates are between 3 and 38%. This reflects the variation in endoscopic methods, histopathological scoring and the studied populations from high-risk geographic regions such has Korea. The prevalence of squamous dysplasia in Western Countries in not well known, since it is generally very difficult to diagnose on white light endoscopy. It can be argued that squamous dysplasia is vastly underdiagnosed in clinical practice as the ratio between oesophageal adenocarcinoma and squamous cell carcinoma in the UK is just over 2:1, however squamous dysplasia is rarely diagnosed.