Better tolerance for colonoscopy or intolerance to virtual colonoscopy?

Abstract

It is with interest that we read the article by Akerkar et al.1Akerkar GA Yee J Hung R McQuaid K. Patient experience and preferences toward colon cancer screening: a comparison of virtual colonoscopy and conventional colonoscopy.Gastrointest Endosc. 2001; 54: 310-315Abstract Full Text Full Text PDF PubMed Scopus (119) Google Scholar on patient tolerance and preference between conventional colonoscopy (CC) and virtual colonoscopy (VC). This is an important issue because VC attempts to create its place in the colorectal cancer screening armamentarium. In our experience, the technique used to achieve colonic insufflation during VC is of extreme importance. As reported by many other groups,2Hara AK Johnson DC Reed JE Ahlquist DA Nelson H MacCarty RL et al.Detection of colorectal polyps with CT colography: initial assessment of sensitivity and specificity.Radiology. 1997; 205: 59-65PubMed Google Scholar, 3Fenlon HM Nunes DP Schroy III, PC Barish MA Clarke PD Ferrucci JT. A comparison of virtual and conventional colonoscopy for the detection of colorectal polyps.N Engl J Med. 1999; 341: 1496-1503Crossref PubMed Scopus (666) Google Scholar, 4Fletcher JG Johnson CD Welch TJ MacCarty RL Ahiquist DA Reed JE et al.Optimization of CT colonography technique: prospective trial in 180 patients.Radiology. 2000; 216: 704-711Crossref PubMed Scopus (303) Google Scholar the authors attained colonic insufflation with a hand-bulb technique to “maximum patient tolerance.” To paraphrase, colonic distention continues until the patient can no longer tolerate this rapid and crude method of distention, that is, not to maximal patient “tolerance” but rather to a degree of “intolerance.” Any screening test that is designed to reach a level of patient intolerance starts at a major disadvantage. In contrast, we achieve colonic distention by gradual insufflation of the colon with an electronic carbon dioxide insufflator, the same kind used for laparoscopic surgery.5Vining DJ Pineau BC. Improved bowel preparation for virtual colonoscopy examinations.Gastroenterology. 1999; 116 ([abstract]): 524AGoogle Scholar Contrary to results published herein, our initial assessment of patient preference during virtual colonoscopy with this technique showed a preference for virtual colonoscopy.6Pineau BC Sevick MA Mikulaninec C Vining DJ. Evaluation of patient preference: virtual colonoscopy versus endoscopic.Gastroenterology. 1999; 116 ([abstract]): 486Abstract Full Text Full Text PDF PubMed Scopus (23) Google Scholar In the current study, the authors assessed patient tolerance with a 7-point Likert scale immediately after VC (before CC), yet ignored these results in the analysis. These data are extremely valuable as they show that the two procedures are comparable with regards to pain (VC: 1.98 [SD 1.38] vs. CC: 1.57 [1.14), discomfort (VC: 1.86 [1.34] vs. CC: 1.45 [0.91]), and lack of respect (VC: 1.86 [0.87] vs. CC: 1.18 [0.61]). The difference in pretest perception between VC and CC is an extremely important factor that could partly explain the results of Akerkar et al.1Akerkar GA Yee J Hung R McQuaid K. Patient experience and preferences toward colon cancer screening: a comparison of virtual colonoscopy and conventional colonoscopy.Gastrointest Endosc. 2001; 54: 310-315Abstract Full Text Full Text PDF PubMed Scopus (119) Google Scholar In our experience, preprocedure questionnaires have shown that patients perceive VC more favorably than CC, an unsurprising finding considering the less invasive nature of VC.6Pineau BC Sevick MA Mikulaninec C Vining DJ. Evaluation of patient preference: virtual colonoscopy versus endoscopic.Gastroenterology. 1999; 116 ([abstract]): 486Abstract Full Text Full Text PDF PubMed Scopus (23) Google Scholar Patients may have tolerated CC better than anticipated leading them to subsequently rate CC better and revising their score for VC to a less favorable one. A measurement of pretest anxiety and perception for VC and CC would have been helpful in this regard. Another possible explanation is that different individuals administered these questionnaires. The post-VC questionnaire was obtained by a radiology technologist whereas a registered nurse (presumably an endoscopy nurse) administered the post-CC questionnaires. Responder bias may have occurred resulting in lower (better) scores for VC during initial assessment and higher subsequent scores. This shortcoming may have been prevented by patient-administered questionnaires or by having the same study coordinator administer both questionnaires. Midazolam only affects anterograde but not retrograde memory,7Twersky RS Hartung J Berger BJ McClain J Beaton C. Midazolam enhances anterograde but not retrograde amnesia in pediatric patients.Anesthesiology. 1993; 78: 51-55Crossref PubMed Scopus (94) Google Scholar hence patients are more likely to recall the VC than CC. Unfortunately, the authors do not report the dosage of the agents used for conscious sedation. In addition, although the time interval between completion of CC and the administration of the questionnaires (tolerance and time trade-off techniques) was not specified, these were completed before discharge from the endoscopy unit. Considering that midazolam has a half-life of 1.3 to 2.2 hours,8Brown CR Sarnquist FH Canup CA Pedley TA. Clinical, electroencephalographic, and pharmacokinetic studies of a water-soluble benzodiazepine, midazolam maleate.Anesthesiology. 1979; 50: 467-470Crossref PubMed Scopus (93) Google Scholar the information captured by these questionnaires was most likely obtained at a time when patients were chemically impaired. The mail-in response may have given a better assessment of tolerability, preference, and time trade-off techniques; however, contrary to the authors statement that this is an “acceptable return rate,” a 28% response rate is clearly inadequate and prevents any conclusions to be drawn from these data. Finally, as the authors stated in the discussion, this predominantly (>97%) male population from a Veterans Affairs Hospital is not representative of the general population. Hence caution should be exercised before widespread misconception develops regarding tolerability and patient acceptance of a potentially extremely valuable tool for colorectal cancer screening. Dr. Vining is the founder, Chief Executive Officer, and major stockholder in PointDx, Inc., a radiological software company. He is also a consultant to EZEM, Inc. Dr. Pineau is a minor stockholder in PointDx, Inc.