To play or not to play – with the adenoma detection rate

A higher adenoma detection rate (ADR) is associated with lower risk of interval cancer [1] [2], and an ADR improvement over time reduces the probability of developing interval cancer [3]. The ADR is the best evaluated and most important quality parameter of screening colonoscopy and therefore it should be as objective as possible. An ADR target of > 20 % [4] was developed from screening populations. Therefore, there is low evidence of whether this rate is applicable to diagnostic and surveillance populations. Actual guideline performance measurements for lower gastrointestinal endoscopy are not limited to screening colonoscopy, and allow application to all levels of endoscopy services; the guidelines indicate that an ADR of 25 % is applicable to all colonoscopies [5].

“This study emphasizes the usefulness of applying the current ADR cutoff level to all types of colonoscopies, irrespectively of indication, in order to avoid the temptation of gaming.”

In this issue of Endoscopy, Rex and Ponugoti investigate the possibility of ADR gaming by changing the colonoscopy indication [6]. In this study, a quality database was assessed for whether combining screening, surveillance, and diagnostic colonoscopies to calculate an overall ADR would alter conclusions about the performance of colonoscopists, compared with the use of ADR based only on screening colonoscopies. In addition, the extent to which one physician could corrupt the screening-only ADR by changing the procedure indication after reviewing the examination was assessed. Among 15 physicians, screening ADRs differed from the overall ADR by a mean of 2.6 percentage points (range 0 – 6.9 percentage points). For one physician, use of the overall ADR rather than the screening only ADR changed the ADR from just below to just above the recommended screening threshold. In the prospective assessment, the single colonoscopist utilized indication gaming in patients with both screening and diagnostic indications to increase his apparent screening-only ADR from 48.4 % to 55.1 %. The higher percentage of male patients [7] undergoing screening compared with diagnostic colonoscopy in the study may explain the higher ADR in the screening colonoscopy group, despite the fact that patients in the diagnostic colonoscopy group were older. Furthermore, diagnostic colonoscopies are often performed for symptoms of pain or change in bowel habit, or for a positive fecal test, making the frequency of diagnostic colonoscopies higher in patients compared with individuals without symptoms in the screening colonoscopy group.

The problem of gaming with the ADR arises because the procedure report and classification of the endoscopy as a screening or a diagnostic procedure is generated after the procedure has been completed – a point in time when the colonoscopist often knows with high probability whether a conventional adenoma has been detected or not. The current system of measuring ADR incentivizes the doctor to call the examination a screening examination if an adenoma has been detected, and a diagnostic examination using the patient’s symptom(s) as the indication if no adenoma was detected. Such behavior, to the extent that it may occur in practice, may lead to gaming, as a higher ADR might also be linked to remuneration in some health care systems. Furthermore, these gaming activities can also be applied on the indication for colonoscopy in patients when stratifying for risk factors. Obesity, diabetes, smoking, or liver cirrhosis are known to increase the risk of adenomas and consecutively the ADR [8] [9]. In addition, the ADR is improved when using high definition endoscopes [10]. The best way to avoid gaming would be to complete the indication section of the report or quality database before the procedure starts.

Detecting an adenoma is only the first step to a successful screening colonoscopy; performing a complete polypectomy with an appropriate technique [11] [12] is crucial to avoid interval cancer, as approximately 30 % of interval cancers develop following an incomplete polypectomy [13].

This study emphasizes the usefulness of applying the current ADR cutoff level to all types of colonoscopies, irrespectively of indication, in order to avoid the temptation of gaming. An effective method of quality assurance would be to incorporate an automatic ADR counting tool into endoscopy software, allowing the ADR to be viewed at the push of a button. Automatic integration of the pathology report into the endoscopy report would be warranted to achieve this function.

• References

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