Diabetic retinopathy treatment cascade and care continuum in the USA: a systematic review
Open accessAbstract
Objectives: To characterise engagement across the diabetic retinopathy (DR) care continuum in the USA using a cascade-of-care framework and identify gaps contributing to preventable vision loss. Design: Systematic review. Data sources: From September to November 2025, with an updated search in March to April 2026 using the same eligibility criteria, we systematically searched Ovid MEDLINE and Ovid Embase supplemented by reviewing reference lists of relevant articles and opportunistic searches of the Centers for Disease Control and Prevention publications. Eligibility criteria: We included English - language US-based cross-sectional, cohort and case–control studies and systematic reviews containing US-based data published between 1 January 2018 and 31 December 2025 relevant to one of the defined DR cascade stages: (1) diagnosis of diabetes, (2) adherence to DR screening, (3) diagnosis of DR, (4) adherence to DR care and (5) DR-related blindness. We included systematic reviews only to inform DR-related blindness, where primary data were limited and excluded them from other stages to avoid double-counting. Exclusion criteria included studies not relevant to one of the defined DR cascade stages and editorial, perspective or commentary pieces. Data extraction and synthesis: Two reviewers independently screened studies, extracted data and assessed risk-of-bias using the Newcastle-Ottawa Scale and Risk of Bias in Systematic Reviews tool. We synthesised data narratively and organised via the DR treatment cascade framework. Results: Of 14 893 studies screened, 46 met the inclusion criteria. Cascade analysis revealed substantial losses in patient engagement at three stages: (1) only 15.5%–78.7% (median 59.4%, IQR 33.9%–74.0%) of individuals with diabetes obtain biennial DR screening; (2) a substantial 54.9%–88.5% (median 70.1%, IQR 62.5%–79.3%) of individuals with DR are unaware of their diagnosis; (3) only 30.9%–62.7% (median 52.0%, IQR 40.9%–59.1%) of individuals diagnosed with DR are initially linked to care and 55.3%–77.8% (median 70.3%, IQR 59.2%–77.7%) have a lapse in DR follow-up. Conclusions: This review identifies major gaps in the DR care continuum, particularly in diagnosis awareness, linkage to care and follow-up adherence. The cascade framework highlights key points of disengagement and provides a basis for prioritising future research.
The claims and statistics of this paper haven’t been checked yet.
Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
The claims and statistics of this paper haven’t been checked yet.
Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
Recent care-cascade evidence shows persistent losses across screening, diagnosis, care adherence, and blindness prevention.
“Recent care-cascade evidence shows persistent losses across screening, diagnosis, care adherence, and blindness prevention (23).”
From From validation to public health impact: implementing equitable AI-enabled diabetic retinopathy screening (2026) · cites this paper as [23]
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
The self-check needs the paper’s full text.
Cites
Preferred Reporting Items for Systematic Reviews and Meta-Analyses: the PRISMA statement
Moher, D., Liberati, A., Tetzlaff, J., Altman, D. G., & for the PRISMA Group (2009) · BMJ · doi:10.1136/bmj.b2535 · Cited by 83,823 · see citing works
Synthesis without meta-analysis (SWiM) in systematic reviews: reporting guideline
Campbell, M., McKenzie, J. E., Sowden, A., Katikireddi, S. V., Brennan, S. E., Ellis, S., Hartmann-Boyce, J., Ryan, R., Shepperd, S., Thomas, J., et al. (2020) · BMJ · doi:10.1136/bmj.l6890 · Cited by 4,628 · see citing works
Global Prevalence of Diabetic Retinopathy and Projection of Burden through 2045
Teo, Z. L., Tham, Y.-C., Yu, M., Chee, M. L., Rim, T. H., Cheung, N., Bikbov, M. M., Wang, Y. X., Tang, Y., Lu, Y., et al. (2021) · Ophthalmology · doi:10.1016/j.ophtha.2021.04.027 · Cited by 2,420 · see citing works
ROBIS: A new tool to assess risk of bias in systematic reviews was developed
Whiting, P., Savović, J., Higgins, J. P. T., Caldwell, D. M., Reeves, B. C., Shea, B., Davies, P., Kleijnen, J., & Churchill, R. (2016) · Journal of Clinical Epidemiology · doi:10.1016/j.jclinepi.2015.06.005 · Cited by 2,272 · see citing works
Narrative Reviews: Flexible, Rigorous, and Practical
Sukhera, J. (2022) · Journal of Graduate Medical Education · doi:10.4300/jgme-d-22-00480.1 · Cited by 1,062 · see citing works
Diabetic Retinopathy: A Position Statement by the American Diabetes Association
Solomon, S. D., Chew, E. Y., Duh, E. J., Sobrin, L., Sun, J. K., VanderBeek, B. L., Wykoff, C. C., & Gardner, T. W. (2017) · Diabetes Care · doi:10.2337/dc16-2641 · Cited by 961 · see citing works
How Effective Are Treatments for Diabetic Retinopathy?
Ferris, F. L. (1993) · JAMA · doi:10.1001/jama.1993.03500100088034 · Cited by 393 · see citing works
Prevalence of Diabetic Retinopathy in the US in 2021
Lundeen, E. A., Burke-Conte, Z., Rein, D. B., Wittenborn, J. S., Saaddine, J., Lee, A. Y., & Flaxman, A. D. (2023) · JAMA Ophthalmology · doi:10.1001/jamaophthalmol.2023.2289 · Cited by 293 · see citing works
Diabetic retinopathy screening: a systematic review of the economic evidence
Jones, S., & Edwards, R. T. (2009) · Diabetic Medicine · doi:10.1111/j.1464-5491.2009.02870.x · Cited by 263 · see citing works
12. Retinopathy, Neuropathy, and Foot Care: Standards of Care in Diabetes—2024
ElSayed, N. A., Aleppo, G., Bannuru, R. R., Bruemmer, D., Collins, B. S., Ekhlaspour, L., Gibbons, C. H., Giurini, J. M., Hilliard, M. E., Johnson, E. L., et al. (2023) · Diabetes Care · doi:10.2337/dc24-s012 · Cited by 245 · see citing works
Canedo, J. R., Miller, S. T., Schlundt, D., Fadden, M. K., & Sanderson, M. (2018) · Journal of Racial and Ethnic Health Disparities · doi:10.1007/s40615-016-0335-8 · Cited by 230 · see citing works
Risk of Bias Evaluation of Cross‐Sectional Studies: Adaptation of the Newcastle‐Ottawa Scale
Carra, M. C., Romandini, P., & Romandini, M. (2026) · Journal of Periodontal Research · doi:10.1111/jre.13405 · Cited by 228 · see citing works
Obeid, A., Su, D., Patel, S. N., Uhr, J. H., Borkar, D., Gao, X., Fineman, M. S., Regillo, C. D., Maguire, J. I., Garg, S. J., et al. (2019) · Ophthalmology · doi:10.1016/j.ophtha.2018.07.027 · Cited by 180 · see citing works
Piyasena, P., Murthy, G. V. S., Yip, J. L. Y., Gilbert, C. E., Zuurmond, M., Pető, T., Gordon, I., Hewage, S. N., & Kamalakannan, S. (2019) · PLoS ONE · doi:10.1371/journal.pone.0198979 · Cited by 180 · see citing works
Obeid, A., Gao, X., Ali, F. S., Talcott, K. E., Aderman, C. M., Hyman, L., Ho, A. C., & Hsu, J. (2018) · Ophthalmology · doi:10.1016/j.ophtha.2018.02.034 · Cited by 143 · see citing works
The Economic Burden of Vision Loss and Blindness in the United States
Rein, D. B., Wittenborn, J. S., Zhang, P., Sublett, F., Lamuda, P. A., Lundeen, E. A., & SAADDINE, J. B. (2021) · Ophthalmology · doi:10.1016/j.ophtha.2021.09.010 · Cited by 131 · see citing works
Risk of Blindness Among Patients With Diabetes and Newly Diagnosed Diabetic Retinopathy
Wykoff, C. C., Khurana, R. N., Nguyen, Q. D., Kelly, S. P., Lum, F., Hall, R. M., Abbass, I. M., Abolian, A. M., Stoilov, I., To, T. M., et al. (2021) · Diabetes Care · doi:10.2337/dc20-0413 · Cited by 130 · see citing works
Diabetic Retinopathy Preferred Practice Pattern®
Lim, J. I., Kim, S. J., Bailey, S. T., Kovach, J. L., Vemulakonda, G. A., Ying, G., & Flaxel, C. J. (2025) · Ophthalmology · doi:10.1016/j.ophtha.2024.12.020 · Cited by 129 · see citing works
Undiagnosed Diabetes in U.S. Adults: Prevalence and Trends
Fang, M., Wang, D., Coresh, J., & Selvin, E. (2022) · Diabetes Care · doi:10.2337/dc22-0242 · Cited by 120 · see citing works
Vision Loss Expert Group of the Global Burden of Disease Study, Curran, K., Pető, T., Jonas, J. B., Friedman, D. S., Kim, J. E., Leasher, J. L., Tapply, I. H., Fernandes, A. G., Cicinelli, M. V., et al. (2024) · Eye · doi:10.1038/s41433-024-03101-5 · Cited by 98 · see citing works
Eye Care Utilization Among Insured People With Diabetes in the U.S., 2010–2014
Benoit, S. R., Swenor, B., Geiss, L. S., Gregg, E. W., & Saaddine, J. B. (2019) · Diabetes Care · doi:10.2337/dc18-0828 · Cited by 97 · see citing works
Socias, M. E., Volkow, N. D., & Wood, E. (2016) · Addiction · doi:10.1111/add.13479 · Cited by 92 · see citing works
Liu, J., Gibson, E., Ramchal, S., Shankar, V., Piggott, K., Sychev, Y., Li, A. S., Rao, P. K., Margolis, T. P., Fondahn, E., et al. (2021) · Ophthalmology Retina · doi:10.1016/j.oret.2020.06.016 · Cited by 88 · see citing works
Eppley, S. E., Mansberger, S. L., Ramanathan, S., & Lowry, E. A. (2019) · Ophthalmology · doi:10.1016/j.ophtha.2019.05.033 · Cited by 76 · see citing works
Barriers to and Facilitators of Diabetic Retinopathy Screening Utilization in a High-Risk Population
Fairless, E. A., & Nwanyanwu, K. H. (2019) · Journal of Racial and Ethnic Health Disparities · doi:10.1007/s40615-019-00627-3 · Cited by 61 · see citing works
Self-citationLoss to Follow-Up Among Patients With Proliferative Diabetic Retinopathy in Clinical Practice
Suresh, R., Yu, H. J., Thoveson, A., Swisher, J., Apolinario, M., Zhou, B., Shah, A. R., Fish, R. H., & Wykoff, C. C. (2020) · American Journal of Ophthalmology · doi:10.1016/j.ajo.2020.03.011 · Cited by 60 · see citing works
Bresnick, G., Cuadros, J. A., Khan, M., Fleischmann, S., Wolff, G., Limon, A., Chang, J., Jiang, L., Cuadros, P., & Pedersen, E. R. (2020) · BMJ Open Diabetes Research & Care · doi:10.1136/bmjdrc-2019-001154 · Cited by 59 · see citing works
An, J., Niu, F., Turpcu, A., Rajput, Y., & Cheetham, T. C. (2018) · Ophthalmic Epidemiology · doi:10.1080/09286586.2018.1424344 · Cited by 55 · see citing works
Gange, W. S., López, J., Xu, B. Y., Lung, K. I., Seabury, S. A., & Toy, B. C. (2021) · Diabetes Care · doi:10.2337/dc21-0228 · Cited by 55 · see citing works
Social Determinants of Health and Perceived Barriers to Care in Diabetic Retinopathy Screening
Ravindranath, R., Bernstein, I. A., Fernandez, K. S., Ludwig, C. A., & Wang, S. Y. (2023) · JAMA Ophthalmology · doi:10.1001/jamaophthalmol.2023.5287 · Cited by 53 · see citing works
Predictors of Lost to Follow-Up in Patients Being Treated for Proliferative Diabetic Retinopathy
Green, M., Tien, T., & Ness, S. D. (2020) · American Journal of Ophthalmology · doi:10.1016/j.ajo.2020.03.023 · Cited by 49 · see citing works
Social determinants of health impacting adherence to diabetic retinopathy examinations
Cai, C. X., Li, Y., Zeger, S. L., & McCarthy, M. L. (2021) · BMJ Open Diabetes Research & Care · doi:10.1136/bmjdrc-2021-002374 · Cited by 48 · see citing works
Baumblatt, J., Fryar, C., Gu, Q., & Ashman, J. (2024) · doi:10.15620/cdc/165794 · Cited by 41 · see citing works
Rural–Urban Disparities in State-Level Diabetes Prevalence Among US Adults, 2021
Khavjou, O., Tayebali, Z., Cho, P., Myers, K. O., & Zhang, P. (2025) · Preventing Chronic Disease · doi:10.5888/pcd22.240199 · Cited by 41 · see citing works
Wang, Y., Zhong, L., Zhai, G., Ding, X. X., Wen, L., Li, D., Zou, B., Feng, K. M., Liang, Y., & Xie, C. (2020) · Ophthalmic Research · doi:10.1159/000508335 · Cited by 40 · see citing works
Lundeen, E. A., Wittenborn, J. S., Benoit, S. R., & SAADDINE, J. B. (2019) · MMWR Morbidity and Mortality Weekly Report · doi:10.15585/mmwr.mm6845a3 · Cited by 39 · see citing works
Lundeen, E. A., Kim, M., Rein, D. B., Wittenborn, J. S., SAADDINE, J. B., Ehrlich, J. R., & Holliday, C. S. (2023) · Diabetes Care · doi:10.2337/dc22-1834 · Cited by 38 · see citing works
Innovative health care mobility services in the US
Wolfe, M. K., & McDonald, N. (2020) · BMC Public Health · doi:10.1186/s12889-020-08803-5 · Cited by 38 · see citing works
Neighborhood Deprivation and Adherence to Initial Diabetic Retinopathy Screening
Yusuf, R., Chen, E. M., Nwanyanwu, K. H., & Richards, B. (2020) · Ophthalmology Retina · doi:10.1016/j.oret.2020.01.016 · Cited by 36 · see citing works
Self-citationRAHMATI, M., SMITH, L., BOYER, L., FOND, G., YON, D. K., LEE, H., SOYSAL, P., PIYASENA, M. P., & PARDHAN, S. (2024) · American Journal of Ophthalmology · doi:10.1016/j.ajo.2024.07.028 · Cited by 34 · see citing works
Lapses in Care Among Patients Assigned to Ranibizumab for Proliferative Diabetic Retinopathy
Maguire, M. G., Liu, D., Bressler, S. B., Friedman, S. M., Melia, M., Stockdale, C. R., Glassman, A. R., Sun, J. K., DRCR Retina Network, Browning, D. J., et al. (2021) · JAMA Ophthalmology · doi:10.1001/jamaophthalmol.2021.4103 · Cited by 32 · see citing works
Awareness of Diabetic Retinopathy: Insight From the National Health and Nutrition Examination Survey
Nwanyanwu, K. H., Nuñez-Smith, M., Gardner, T. W., & Desai, M. M. (2021) · American Journal of Preventive Medicine · doi:10.1016/j.amepre.2021.05.018 · Cited by 30 · see citing works
Self-citationRegional disparities in type 2 diabetes prevalence and associated risk factors in the United States
Neupane, S., Florkowski, W. J., Dhakal, U., & Dhakal, C. (2024) · Diabetes Obesity and Metabolism · doi:10.1111/dom.15797 · Cited by 30 · see citing works
Longitudinal Trends and Disparities in Diabetic Retinopathy Within an Aggregate Health Care Network
Markle, J. C., Shaia, J. K., Araich, H., Sharma, N., Talcott, K. E., & Singh, R. P. (2024) · JAMA Ophthalmology · doi:10.1001/jamaophthalmol.2024.0046 · Cited by 28 · see citing works
Gange, W. S., Xu, B. Y., Lung, K. I., Toy, B. C., & Seabury, S. A. (2020) · Ophthalmology Retina · doi:10.1016/j.oret.2020.07.004 · Cited by 28 · see citing works
Twenty-Year Trends in Prevalence and Incidence of Diabetic Retinal Disease
VanderBeek, B. L., Yu, Y., Cardillo, S., & Hubbard, R. A. (2025) · Ophthalmology · doi:10.1016/j.ophtha.2025.01.022 · Cited by 26 · see citing works
Chen, A. J., Hwang, V., Law, P. Y., Stewart, J. M., & Chao, D. L. (2018) · Ophthalmic Epidemiology · doi:10.1080/09286586.2018.1504311 · Cited by 22 · see citing works
Health Disparities in Lapses in Diabetic Retinopathy Care
Cai, C. X., Tran, D., Tang, T., Liou, W., Harrigian, K., Scott, E., Nagy, P. G., Kharrazi, H. H. K., Crews, D. C., & Zeger, S. L. (2023) · Ophthalmology Science · doi:10.1016/j.xops.2023.100295 · Cited by 21 · see citing works
Khurana, R. N., Wang, J. C., Zhang, S., Li, C. H., & Lum, F. (2024) · Ophthalmology Retina · doi:10.1016/j.oret.2024.04.016 · Cited by 21 · see citing works
PATIENTS PRESENTING EMERGENTLY WITH PROLIFERATIVE DIABETIC RETINOPATHY
Hinkle, J. W., Flynn, H. W., Banta, J. T., & Vanner, E. A. (2019) · Retina · doi:10.1097/iae.0000000000002481 · Cited by 20 · see citing works
The functional burden of diabetic retinopathy in the United States
Nagda, D., Mitchell, W. G., & Zebardast, N. (2021) · Graefe s Archive for Clinical and Experimental Ophthalmology · doi:10.1007/s00417-021-05210-3 · Cited by 15 · see citing works
Place, Race, and Lapses in Diabetic Retinopathy Care
Tang, T., Tran, D., Han, D., Zeger, S. L., Crews, D. C., & Cai, C. X. (2024) · JAMA Ophthalmology · doi:10.1001/jamaophthalmol.2024.0974 · Cited by 14 · see citing works
Silva, P. S., Cavallerano, J. D., Sun, J. K., Tolson, A. M., Tolls, D. B., Abrahamson, M. J., Aiello, L. M., & Aiello, L. P. (2024) · Diabetes Care · doi:10.2337/dc23-2282 · Cited by 12 · see citing works
Chen, J., Zhu, Y., Li, Z., Zhang, Y., Ye, G., Chen, K., Zhuo, X., Zhang, S., Lin, L., & Zhuo, Y. (2023) · Diabetes Research and Clinical Practice · doi:10.1016/j.diabres.2023.110823 · Cited by 12 · see citing works
Watane, A., Kalavar, M., Vanner, E. A., Cavuoto, K. M., & Sridhar, J. S. (2020) · Retina · doi:10.1097/iae.0000000000003037 · Cited by 9 · see citing works
Bonilla-Escobar, F. J., Eibel, M. R., Le, L. M., Gallagher, D. S., & Waxman, E. L. (2024) · BMC Ophthalmology · doi:10.1186/s12886-024-03581-9 · Cited by 9 · see citing works
Luo, S., Lock, L. J., Xing, B., Wingelaar, M. J., Channa, R., & Liu, Y. (2022) · Telemedicine Journal and e-Health · doi:10.1089/tmj.2022.0391 · Cited by 7 · see citing works
Diabetes prevalence, awareness, and control in the United States, 2017-2023
Harding, J. L., Hu, C., Varghese, J. S., Carrillo-Larco, R. M., & Ali, M. K. (2025) · Diabetes & Metabolism · doi:10.1016/j.diabet.2025.101659 · Cited by 6 · see citing works
Khurana, R. N., Wang, J. C., Zhang, S., Li, C. H., & Lum, F. (2025) · Ophthalmology Retina · doi:10.1016/j.oret.2025.05.033 · Cited by 6 · see citing works
Lee, D. C., Ross, L., ARIAS, C. Q., RONY, M., Patel, R., JENSEN, E., Petcu, R., IMAS, D. M., Elbel, B. D., Thorpe, L. E., et al. (2024) · BMJ Open · doi:10.1136/bmjopen-2023-080831 · Cited by 4 · see citing works
Frimpong, A. A., Granados, A., Chang, T., Fu, J. J., Moore, S. G., Applebaum, S. S., Adepoju, B., Kaur, M., Krishnan, V. H., Levi, A., et al. (2025) · JMIR Formative Research · doi:10.2196/65893 · Cited by 4 · see citing works
Self-citationGeographic variation in diabetic retinopathy screening within the Veterans Health Administration
Davis, M. L., Snider, M. J. E., Hunt, K. J., Medunjanin, D., Neelon, B., & Maa, A. Y. (2023) · Primary care diabetes · doi:10.1016/j.pcd.2023.06.004 · Cited by 4 · see citing works
Access to a Patient Portal is Associated with a Higher Rate of Diabetic Eye Examination Completion
Gumustop, S., Popelka, A., & Ramsey, D. J. (2024) · Ophthalmic Epidemiology · doi:10.1080/09286586.2024.2406506 · Cited by 4 · see citing works
Deans, J. R., George, R., Aldaas, K. M., Buren, E. D. V., & Ulrich, J. N. (2022) · Retina · doi:10.1097/iae.0000000000003540 · Cited by 3 · see citing works
Duration and Frequency of Lapses in Care Among Patients with Proliferative Diabetic Retinopathy
Applebaum, S. S., Fu, J. J., & Nwanyanwu, K. H. (2025) · Ophthalmic Epidemiology · doi:10.1080/09286586.2025.2463067 · Cited by 3 · see citing works
Self-citation
Flagged first, then by citations
Cited by
Sorted by citations
Chen, J., & Chen, B. (2026) · Frontiers in Public Health · doi:10.3389/fpubh.2026.1976572
RETINOPATIA DIABÉTICA: ABORDAGEM CLÍNICA E NOV AS PERSPECTIV AS TERAPÊUTICAS
Porto, D. J., WESTPHALEN, S. L., Matter, D. C., Barboza, I. P., & Mello, L. R. D. M. (2026) · Editora Pasteur eBooks · doi:10.59290/5159320262
- Authors
- Fu, J. J., Applebaum, S. S., Granados, A., & Nwanyanwu, K.
- Affiliations
- Yale University (US)
- Corresponding author
- Nwanyanwu, Kristen
- Venue
- BMJ Open
- Publisher
- BMJ
- Published
- 2026-06
- Volume
- 16
- Issue
- 6
- Pages
- e117683
- ISSN
- 2044-6055 (ISSN-L)
- PMC
- PMC13264893
- OpenAlex
- W7164219225
- Cited by
- 1
- References
- 62
- Citations by year
- 2026: 1
- FWCI
- 1.76
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- Locations
- BMJ Open (publishedVersion, cc-by-nc)
- PubMed (publishedVersion)
- PubMed Central (publishedVersion, cc-by-nc)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Funders
- James G. Hirsch Endowed Medical Student Research Fellowship
- Research to Prevent Blindness
- National Eye Institute (1 K23 EY030530-01)
- Topics
- Health Sciences › Medicine › Ophthalmology › Retinal Diseases and Treatments
- Health Sciences › Medicine › Radiology, Nuclear Medicine and Imaging › Retinal Imaging and Analysis
- Health Sciences › Medicine › Epidemiology › Ophthalmology and Visual Impairment Studies
- Keywords
- diabetic retinopathy, continuum of care, cascade of care, diabetic retinopathy screening, screening adherence, diabetes diagnosis, retinopathy diagnosis, linkage to care, follow-up adherence, blindness prevention, patient engagement, United States, health service gaps, health equity, racial and ethnic disparities, geographic disparities, socioeconomic disparities, diabetes self-management education
- MeSH terms
- Blindness, Continuity of Patient Care, Diabetic Retinopathy, Humans, United States
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review
