Too soon or too late?: Choosing the right screening test intervals

James A. Dickinson; Guylène Thériault; Harminder Singh; Roland Grad; Neil R. Bell; Olga Szafran

doi:10.46747/cfp.6702100

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Figure 1.
Screening detection capability based on tumour biology and growth rates: Growth rates of 4 tumours are displayed from the time the first tumour cells appear while the tumour is not yet detectable (microscopic); when it can be detected as localized (confined to the organ) and most likely to be curable; regional (after the tumour spreads beyond the organ) where it might not be curable; and to the point when metastases and death occur. Tumour A remains undetectable and without morbidity during the patient’s lifetime. Tumour B grows until it becomes detectable but never causes symptoms or leads to death. Tumours A and B represent low-risk indolent tumours or IDLEs (indolent lesions of epithelial origin). Tumour C is destined to become metastatic and fatal but can be detected while still curable. Tumour D is destined to become metastatic but grows so quickly that by the time it can be detected, it might no longer be curable. Among these 4 tumours, only the patient with tumour C benefits from screening.
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Figure 2.
Effect of 2 screening regimens on disease prevalence: Prevalence of a disease increases with age (green line). Prevalence is reduced by a screening test with sensitivity of 0.75 at age 60, when benefit is considered optimal compared with harms caused. Thereafter, new incidence of disease in the remaining population occurs at the original expected rate. The model shows the effects of repeat screening tests when prevalence rises to the same level (blue line) or every 2 y from age 60 to age 70 (red line). Note that in prevalence-based screening, intervals might vary. In regular frequent screening, subsequent screens have less benefit, although during this period the prevalence of undetected disease is lower; 6 screens have fewer long-term effects compared with 3 screens at longer intervals.

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Table 1.

Evidence for intervals of repeat screening

DISEASE OR CONDITION	SOURCE OF RECOMMENDATION	SOURCE OF EVIDENCE	AGE TO START OR STOP SCREENING	INTERVAL RECOMMENDATION
Cancer
Cervical
• Papanicolaou tests	CTFPHC guideline⁸	International Agency for Research on Cancer⁹	25-70 y	3 y
• HPV tests	American Cancer Society guideline¹⁰	American Cancer Society¹⁰	25-70 y	5 y
Breast	CTFPHC guideline¹	Meta-analysis¹¹	50-75 y	2-3 y
Colorectal	CTFPHC guideline¹²	Trials^13,14	50-74 y	2 y
Lung	European expert group¹⁵	Trials^16,17	60-80 y	Annually at first, then every 2 or more y
Cardiovascular
Hypertension and dyslipidemia	European expert group¹⁸^{^*}	Modeling using Whitehall study¹⁸	> 40 y	Low risk: 7 y Intermediate risk: 4 y Intermediate to high risk: 1 y
Diabetes	CTFPHC guideline¹⁹^{^†}	Meta-analysis¹⁹	40 y	Low risk: no screen Medium risk: every 3-5 y High risk: annual
Other
Osteoporotic fracture	Cohort study²⁰	Gourlay et al²⁰	Women: ≥ 65 y Men: insufficient evidence	T-score >-1.5: 15 y T-score -1.5 to -1.99: 5 y T-score -2 to -2.49: 1 y
Osteoporotic fracture	Cohort study²¹	Crandall et al²¹		Screen once (no repeat)
Abdominal aortic aneurysm	CTFPHC guideline²	Meta-analysis²	Men: 65 y	Once (no repeat)

ASCVD—atherosclerotic cardiovascular disease, CTFPHC—Canadian Task Force on Preventive Health Care, FINDRISC—Finnish Diabetes Risk Score, HPV—human papillomavirus.
↵*Cardiovascular risk was defined by the ASCVD calculator as the 10-year risk of cardiovascular events (myocardial infarction, death from coronary artery disease, fatal or nonfatal stroke). Low risk was defined as less than 2.5%. Intermediate risk was from 2.5% to less than 5%. Intermediate to high risk was from 5% to 10%. High risk was greater than 10%, which was the threshold for active management.
↵^†Diabetes risk was determined by FINDRISC²²: ≤ 14 points: low risk, no screen; 15 to 20 points: medium risk, screen every 3 to 5 y; ≥ 21 points: high risk, screen annually.

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Table 2.
Effectiveness of cervical cancer screening in women aged 35 to 64 y by interval since last screening
SCREENING INTERVAL, Y REDUCTION IN CUMULATIVE INCIDENCE, % NO. OF TESTS
  1 93.5 30
  2 92.5 15
  3 90.8 10
  5 83.6   6
10 64.1   3
Data from the IARC Working Group on Evaluation of Cervical Cancer Screening Programmes.⁹