Assessment of the efficacy of the education of radiographers who interpret CT‐colonography examinations: a systematic review protocol

Review question/objective The objective of this review is to assess the effectiveness of the training of radiographers who learn to interpret CT‐colonography (CTC) with the reference standard, optical colonoscopy (OC) in terms of their diagnostic performance. The reference standard (OC) is used to determine if the CTC diagnosis is correct. Background Colorectal cancer (CRC) represents an important health problem in Western countries. In 2012, there were approximately 143,000 newly diagnosed cases of CRC in the US and nearly 52,000 deaths associated with this disease.1 In Europe, almost 413,000 individuals are newly diagnosed with CRC and about half of these patients will die of the disease; making CRC the second leading cause of cancer deaths in both Europe and the United States.2 Most CRCs are adenocarcinomas and arise from benign adenomatous polyps that develop slowly over 10‐20 years,3‐7 and the malignant transformation is related to polyp size.8 The risk of malignancy is approximately 1% for adenomas smaller than 10mm; however the risk for adenomas larger than 10mm increases to 15% and for adenomas larger than 20mm it increases up to 40% for transforming into a malignancy within 10 years.6,7 At the present time, several diagnostic modalities are used for colonic evaluation including rectoscopy, flexible sigmoideoscopy, OC, fecal occult blood test, double contrast barium enema, magnetic resonance colonography and CTC. However, OC is considered to be the gold standard due to a high diagnostic accuracy and the option of therapeutic intervention. Although OC is an excellent examination technique, it has several disadvantages in the form of serious complications, such as colonic perforation,9 and the need for sedation and post procedural monitoring.10 CTC has attracted multidisciplinary attention as a minimally invasive structural evaluation of the entire colon and rectum for the detection of polyps and cancers. CTC represents a modified CT‐examination in a patient who has undergone bowel preparation and colonic distension, in which the images are interpreted using advanced two‐dimensional (2D) and three‐dimensional (3D) display techniques. The examination was first introduced in 1994 by Vinning,11 and since the introduction there have been further advancements in CTC technology. Multi detector CT now permits image acquisition of thin 1‐ to 2‐mm slices of the entire large intestine, well within breath‐hold imaging times. Computer imaging graphics allow for visualization of 3D endoscopic flight paths through the inside of the colon, which are simultaneously viewed with interactive multiplanar 2D images. The integrated use of the 3D and 2D techniques allows for ease of polyp detection, as well as characterization of lesion density and location.There have been several meta‐analyses of CTC accuracy that have analyzed studies which included low‐ and increased prevalence subjects, or symptomatic patients.12‐15 These meta‐analyses showed 85‐93% sensitivity on a per‐patient basis for larger polyps and a specificity of 95% or greater. However, there has been variability of accuracy among several studies. Two studies have cast doubts on the accuracy of CTC, reporting poor per‐patient sensitivity, even for lesions greater than 10mm in size; though the methodology of both of these studies has been criticized, particularly with regard to the Cotton trial, on the basis of the lack of experience of the reporting radiologists.12,16 Nevertheless, other studies have shown better results. A landmark study, employing meticulous methodology and one of the few large studies of CTC in asymptomatic average‐risk individuals, published by Pickhardt et al., reported excellent accuracy for CTC, equal to or better than OC.4 This group's results have been attributed to state of the art scanning and software, using 3D as the primary read and fecal tagging. Similarly, the published American College of Radiology Imaging Network (ACRIN) multi‐center trial reported excellent sensitivity for large adenomas and cancers.17 A further study by Kim et al., compared the diagnostic yield from parallel OC and CTC screening programs and found similar detection rates of advanced neoplasia in the two groups.18 Some studies have documented wide inter‐reader variability between radiologists interpreting CTC‐examinations.19 One solution to prevent wide inter‐reader variability could be by using two radiologists to double‐read every CTC‐examination, as this has been shown to improve the overall accuracy of CTC significantly.20 However double‐reading by radiologists could increase the interpretation time and create significant logistical challenges in busy diagnostic imaging departments. The shortage of radiologists makes this an impractical long‐term solution; therefore diagnostic imaging departments should ensure efficient work routines and assess the possibilities for assigning tasks to less educated personnel groups such as radiographers.21 Until now, most research has focused on the technical capabilities of CTC; however, it is increasingly being realized that reader experience and training are equally important.22 In terms of how teaching cases are selected and presented, there is a wide disparity; however there is an emerging consensus that there is a variable learning curve associated with interpreting CTC findings.23 This implies that interpretation performance improves as the number of interpreted cases increases.24 At the time of writing, there is no evidence‐based guideline for training in interpreting CTC examinations, although the literature suggests that the interpretation of at least 50 validated CTC cases for trained readers and 75 cases for novice readers may be required to achieve high levels of performance.10,22,25,26 Three studies in particular investigated the performance of radiographers.23,25,27 For this reason, it is of interest to conduct a systematic review concerning studies including the education of radiographers who interpret CTC. At the present time, no similar study has been published. A preliminary search of PubMed, JBI Database of Systematic Reviews and Implementation Reports, CINAHL, Cochrane Library, AHRQ (Agency for Healthcare Research and Quality) and Medline did not reveal any systematic reviews on this topic.