Health Technology Assessment (Sep 2018)
Adjunctive colposcopy technologies for assessing suspected cervical abnormalities: systematic reviews and economic evaluation
Abstract
Background: Dynamic Spectral Imaging System (DySIS)map (DySIS Medical Ltd, Edinburgh, UK) and ZedScan (Zilico Limited, Manchester, UK) can be used adjunctively with conventional colposcopy, which may improve the detection of cervical intraepithelial neoplasia (CIN) and cancer. Objectives: To systematically review the evidence on the diagnostic accuracy, clinical effectiveness and implementation of DySISmap and ZedScan as adjuncts to standard colposcopy, and to develop a cost-effectiveness model. Methods: Four parallel systematic reviews were performed on diagnostic accuracy, clinical effectiveness issues, implementation and economic analyses. In January 2017 we searched databases (including MEDLINE and EMBASE) for studies in which DySISmap or ZedScan was used adjunctively with standard colposcopy to detect CIN or cancer in women referred to colposcopy. Risk of bias was assessed with the Quality Assessment of Diagnostic Accuracy Studies (QUADAS)-2 tool. Summary estimates of diagnostic accuracy were calculated using bivariate and other regression models when appropriate. Other outcomes were synthesised narratively. A patient-level state-transition model was developed to evaluate the cost-effectiveness of DySISmap and ZedScan under either human papillomavirus (HPV) triage or the HPV primary screening algorithm. The model included two types of clinics [‘see and treat’ and ‘watchful waiting’ (i.e. treat later after confirmatory biopsy)], as well as the reason for referral (low-grade or high-grade cytological smear). Sensitivity and scenario analyses were undertaken. Results: Eleven studies were included in the diagnostic review (nine of DySISmap and two of ZedScan), three were included in the clinical effectiveness review (two of DySISmap and one of ZedScan) and five were included in the implementation review (four of DySISmap and one of ZedScan). Adjunctive DySISmap use was found to have a higher sensitivity for detecting CIN grade 2+ (CIN 2+) lesions [81.25%, 95% confidence interval (CI) 72.2% to 87.9%] than standard colposcopy alone (57.91%, 95% CI 47.2% to 67.9%), but with a lower specificity (70.40%, 95% CI 59.4% to 79.5%) than colposcopy (87.41%, 95% CI 81.7% to 91.5%). (Confidential information has been removed.) The base-case cost-effectiveness results showed that adjunctive DySISmap routinely dominated standard colposcopy (it was less costly and more effective). The only exception was for high-grade referrals in a watchful-waiting clinic setting. The incremental cost-effectiveness ratio for ZedScan varied between £272 and £4922 per quality-adjusted life-year. ZedScan also dominated colposcopy alone for high-grade referrals in see-and-treat clinics. These findings appeared to be robust to a wide range of sensitivity and scenario analyses. Limitations: All but one study was rated as being at a high risk of bias. There was no evidence directly comparing ZedScan with standard colposcopy. No studies directly compared DySIS and ZedScan. Conclusions: The use of adjunctive DySIS increases the sensitivity for detecting CIN 2+, so it increases the number of high-grade CIN cases that are detected. However, it also reduces specificity, so that more women with no or low-grade CIN will be incorrectly judged as possibly having high-grade CIN. The evidence for ZedScan was limited, but it appears to increase sensitivity and decrease specificity compared with colposcopy alone. The cost-effectiveness of both adjunctive technologies compared with standard colposcopy, under both the HPV triage and primary screening algorithms, appears to be favourable when compared with the conventional thresholds used to determine value in the NHS. Future work: More diagnostic accuracy studies of ZedScan are needed, as are studies assessing the diagnostic accuracy for women referred to colposcopy as part of the HPV primary screening programme. Study registration: This study is registered as PROSPERO CRD42017054515. Funding: The National Institute for Health Research Health Technology Assessment programme.
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