A national programme proposes cervical cancer screening by VIA (Visual Inspection with Acetic acid) every 5 years in women aged 30–65. To decide the optimal screening interval, the most critical disease characteristic is:

• A The incidence rate of cervical cancer in the target population
• B The sensitivity of VIA test in detecting CIN 2+
• C The specificity of the test to reduce unnecessary colposcopies
• D The sojourn time (duration of detectable preclinical phase) of CIN 3 / pre-invasive cervical disease ✓

Explanation

Sojourn time (the interval during which the disease is in a detectable preclinical phase before becoming symptomatic) is the key parameter determining screening interval: the interval should be shorter than the sojourn time to reliably detect disease before symptomatic progression. For cervical precancer (CIN 3), the mean sojourn time is estimated at 5–15 years, justifying 3–5 year intervals. Incidence guides target population size but not interval. Sensitivity affects the per-screen detection rate but not the biologically ideal interval.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.