PRINCIPLE | ANAL HPV SCREENING | CANCER BLOOD TEST | WHOLE-BODY MRI | DEPRESSION SCREENING TEST |
---|---|---|---|---|
For diseases or conditions | ||||
1. Epidemiology of the disease must be understood and it must be an important health problem | Anal cancer is a rare disease: Canada has 670 new cases/y and 181 deaths.29 Anal cancer is partly understood; is HPV related; and has higher prevalence in those having anal intercourse and in PLWHIV | Cancers overall are common past middle age, but outside of breast, colon, prostate, and lung cancers, new cases of each type are rare. Each has different characteristics and must be evaluated separately | MRI will find a variety of diseases, some of which may be serious. It also finds many variations that are best left alone (“incidentalomas”). Even if some incidentalomas are cancers, we do not know if treating these actually changes outcomes | Moderate prevalence, but new serious depression is uncommon |
2. Natural history should be understood and a preclinical phase must be detectable | Like other HPV infections, some progress, others may resolve. Treatment of PLWHIV with HSIL (mean age 51 y) reduces 4-y progression to cancer from 0.95% to 0.40%30 | For some cancers this is true. Maybe this test will prove able to detect other early-stage cancers | For some detectable conditions, yes, but many incidentalomas are better not investigated | Natural history of most depression is for resolution within 3-6 mo.31 Much of what is found by screening is unhappiness with a life crisis. Many cases are self-resolving, with “talk therapy” |
3. Target population for screening must be defined | PLWHIV and other immunosuppressed populations are at higher risk | Insufficient information to judge at what age to start and stop, and frequency for testing | Insufficient information to judge at what age to start and stop, and frequency for testing | Groups at high risk are identifiable (eg, postpartum women who are immigrants) |
For tests or interventions | ||||
4. Screening test performance characteristics: accurate, safe, acceptable, affordable | Not yet clear. Specificity low: acceptable to some members of at-risk populations, but follow-up rates low32 | No information yet. Likely acceptable | Too much information is possible: minute variations are found and lead to further investigations. Interreader variations are likely high | PHQ-9 often used in clinical situations. Safe and acceptable. Sensitivity and specificity of 85%, but when prevalence is low (eg, 10%) predictive value is low (eg, 40%). Unclear whether effective33 |
5. Interpretation of screening test results: clear thresholds | Not yet clear34 | Not yet fully described. Will need careful calibration | Not clear | Threshold score of 10 often used for PHQ-9, but then needs clinical assessment to make diagnosis |
6. Postscreening test options: agreed-upon course of action for follow-up and treatment to improve outcomes | High-resolution anoscopy and treatment of HSILs30 | Some may follow standard protocols, others not yet worked through | Variable, depending on anatomic location and features | If clinical assessment confirms the diagnosis, treat with counseling, antidepressant medication, or both |
For programs or systems | ||||
7. Screening program infrastructure: adequate existing resources or plan to develop resources sufficient for all | Anoscopy assessment and treatment clinics not widely available; pathologists not widely trained in reading these tests | No for most of the proposed screening target diseases. For some, infrastructure is available but it is unclear how to use it purposefully with earlier detection | Not enough access for patients with clear indications requiring MRI investigation. Private MRI available in large centres | Family physician treatment, referral to mental health staff or psychologist: not readily available |
8. Screening program coordination and integration: coordinated and integrated into broader health system | No | No | Done privately, ≥$2000. Any findings must be dealt with in standard facilities | Usually |
9. Screening program acceptability and ethics: all components should be ethically acceptable to participants and professionals, and methods should exist to ensure informed choice | No | Not worked through | Without understanding possible risks, cannot engage in informed consent | Most patients want dialogue about how they feel, not checklists like PHQ-9 |
10. Screening program benefits and harms: benefits should be greater than harms | Unclear | Not yet demonstrated | Few benefits, harms likely greater35 | Not yet demonstrated36 |
11. Economic evaluation of screening program: economic evaluation should assess full costs of operating screening program compared with opportunity costs of allocating resources to alternatives | Unknown currently. May be useful among patients at high risk age >40 y | Unknown | Profitable for private facilities but effort and cost needed to follow up abnormalities most likely shift the balance toward more opportunity costs | High opportunity cost36 |
12. Screening program quality and performance management: screening program should have clear goals and objectives and monitor for quality control and performance targets | Not yet available | Not yet possible | Radiology quality improvement is variable in Canada20,21 | Not applicable |
HPV—human papillomavirus, HSIL—high-grade squamous intraepithelial lesion, MRI—magnetic resonance imaging, PHQ-9—Patient Health Questionnaire–9, PLWHIV—people living with HIV.