Abstract
ObjectivesTo determine if polyp detection at computed tomographic colonography (CTC) is associated with (a) the number of CTC examinations interpreted per day and (b) the length of time spent scrutinising the scan.MethodsRetrospective observational study from two hospitals. We extracted Radiology Information System data for CTC examinations from Jan 2012 to Dec 2015. For each examination, we determined how many prior CTCs had been interpreted by the reporting radiologist on that day and how long radiologists spent on interpretation. For each radiologist, we calculated their referral rate (proportion deemed positive for 6 mm+ polyp/cancer), positive predictive value (PPV) and endoscopic/surgically proven polyp detection rate (PDR). We also calculated the mean time each radiologist spent interpreting normal studies (“negative interpretation time”). We used multilevel logistic regression to investigate the relationship between the number of scans reported each day, negative interpretation time and referral rate, PPV and PDR.ResultsFive thousand one hundred ninety-one scans were interpreted by seven radiologists; 892 (17.2%) were reported as positive, and 534 (10.3%) had polyps confirmed. Both referral rate and PDR reduced as more CTCs were reported on a given day (p < 0.001), the odds reducing by 7% for each successive CTC interpreted. Radiologists reporting more slowly than their colleagues detected more polyps (p = 0.028), with each 16% increase in interpretation time associated with a 1% increase in PDR. PPV was unaffected.ConclusionsReporting multiple CTCs on a given day and rapid CTC interpretation are associated with decreased polyp detection. Radiologists should be protected from requirements to report too many CTCs or too quickly.Key Points• CT colonography services should protect radiologists from a need to report too fast (> 20 min per case) or for too long (> 4 cases consecutively without a break).• Professional bodies should consider introducing a target minimum interpretation time for CT colonography examinations as a quality marker.
Highlights
Year on year, medical imaging increases inexorably [1, 2], outstripping growth in radiology staffing [3]
We regarded the presence of any endoscopically or surgically proven polyp or cancer as a truepositive Computed tomographic colonography (CTC) finding, regardless of location or final histology. We estimated their potential Breferral rate^, their positive predictive value (PPV; defined as the percentage of cases in which a polyp or cancer was found if confirmatory testing was done) and their polyp detection rate (PDR; defined as the proportion of cases in which a polyp or cancer was confirmed, relative to the total number of cases interpreted)
The radiologist with the highest PDR had the lowest PPV, and the radiologist with the highest PPV had the second lowest PDR, but overall there was no consistent relationship between radiologist-level PPV and PDR
Summary
Medical imaging increases inexorably [1, 2], outstripping growth in radiology staffing [3]. Radiologists are under increasing pressure to report more studies more rapidly, while maintaining accuracy. Computed tomographic colonography (CTC) is both complex and time-consuming to interpret It is fatiguing, as the interpretive task (of flying or scrolling through the colon) is repetitive, and the majority of examinations are negative for the primary target condition (colorectal cancer or large polyps) [6,7,8,9], a phenomenon that is known to reduce vigilance [10]. It is tempting to interpret CTC rapidly, for the final few examinations in a given reporting session. This may well reduce detection rates; in a laboratory environment, more rapid fly-through at endoluminal CTC reduces both the proportion of colonic mucosa viewed by the radiologist and the polyp detection rate [11].
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