Introduction
Optical diagnosis (OD) allows real-time endoscopic assessment of polyp histology and holds promise for enhancing colorectal cancer screening. In 2022, ESGE recommended OD performance thresholds for the leave-in-situ strategy (>90% sensitivity/>80% specificity for diminutive polyps in the rectosigmoid) as well as for the resect and discard strategy (>80% sensitivity/>80% specificity for colorectal diminutive adenomas)1. However, guidance on small polyps (5-9mm) is lacking and it is unknown if high adenoma detection rate (ADR) translates to high OD performance. In Sweden, screening colonoscopies are performed by experienced endoscopists but formal training in OD is not required.
Aims & Methods
This study aimed to evaluate the diagnostic performance of OD for diminutive (<5 mm) and small (5–9 mm) colorectal adenomas, and to assess the relationship between ADR and OD accuracy. Data were retrieved from the Swedish national colorectal cancer screening registry (SveReKKS), including colonoscopies performed between April 2019 and December 2023. Registration of screening colonoscopies is mandatory, but registration of OD is not. Polyps where both OD and histopathology were available were included. Diagnostic performance was assessed using accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for diminutive and small adenomas. Subgroup analyses were performed for rectosigmoid adenomas. ADR was compared between endoscopists who used OD and those who did not. Among endoscopists with >30 OD cases, the correlation of ADR and diagnostic accuracy (measured with Youden's index) was assessed.
Results
Among 12,358 colonoscopies, 24,685 polyps and cancers were identified. OD and histopathological results were available for 3,807 polyps, of which 1,092 were diminutive and 1,460 small polyps. For all diminutive adenomas, OD had 89.0% sensitivity, and 64.0% specificity. In the rectosigmoid, sensitivity was 91.6% and specificity 69.6%. For small adenomas, OD showed 94.4% sensitivity and 76.1% specificity. In the rectosigmoid, sensitivity was very high, 97.1%, but specificity was low, 61.2%. A summary of predictive measures is provided in Table 1. None of the small adenomas falsely diagnosed as non-adenomas by OD harboured high-grade dysplasia or cancer.
Endoscopists that consistently used OD had considerably higher ADR (67% [95%CI 65-69%]) compared to those who never used OD (50% [95%CI 48-52%]). Despite their high ADR, only 3 of 25 (12%) of endoscopists using OD had both high sensitivity and specificity (>80%) in OD of all diminutive adenomas. Furthermore, no correlation was found between ADR and OD accuracy measured by Youden’s index (R² = 0.01).
| Accuracy
(95 % CI)
| Sensitivity
(95 % CI)
| Specificity
(95 % CI)
| PPV
(95 % CI)
| NPV
(95 % CI)
|
All Diminutive Adenomas
(n=1,092) | 80.0
(77.5-82.4)
| 89.0
(86.4-91.2)
| 64.0
(59.1-68.8)
| 81.5
(78.6-84.2)
| 76.5
(71.6-81.0)
|
Rectosigmoid Diminutive Adenomas
(n=359) | 81.3
(76.9-85.2)
| 91.6
(86.8-95.1)
| 69.6
(62.1-76.5) | 77.4
(71.6-81.0)
| 88.0
(81.2-93.0) |
All Small Adenomas
(n=1,460) | 89.7
(88.0-91.2) | 94.4
(82.8-95.7) | 76.1
(71.4-80.3) | 91.9
(90.2-93.4) | 82.4
(78.0-86.3) |
Rectosigmoid Small Adenomas
(n=629) | 90.5
(87.9-92.6) | 97.1
(95.2-98.4) | 61.2
(51.7-70.1) | 91.7
(89.1-93.9) | 82.6
(72.9-89.9) |
Conclusion
In this nationwide screening cohort, OD demonstrated high sensitivity but limited specificity, indicating that leave-in-situ and resect and discard strategies cannot be implemented yet in the Swedish screening program. However, the absence of missed HGD/cancer in small polyps is encouraging, as it indicates abovementioned resection strategies may be considered not only for diminutive adenomas. The absence of a link between high ADR and OD accuracy highlights the need for targeted OD training and performance monitoring when implementing OD in population-based screening programs.
References
Houwen BBSL, Hassan C, Coupé VMH, et al. Definition of competence standards for optical diagnosis of diminutive colorectal polyps: European Society of Gastrointestinal Endoscopy (ESGE) Position Statement. Endoscopy. 2022;54(1):88-99. doi:10.1055/a-1689-5130
