Page 55 - Screening for Cervical Cancer: Systematic Evidence Review

Chapter III. Results

detection of precancerous lesions when compared in a single screening session to conventionally

prepared and interpreted cytology. However, no data are available to assess their long-term

benefit if implemented in a screening system. Cervical dysplasia is at times a spontaneously

resolving condition or, if progressive, a slowly developing condition. For precisely these

reasons, the full system of screening—i.e., the modality used, the interval for testing, and the

decisionmaking process related to evaluation and treatment—need to be evaluated in toto to

compare performance characteristics properly. Prospective measurement of outcomes is

essential to guiding policy.

Costs

A central goal of the Evaluation of Cervical Cytology evidence report was modeling the

effects on total health care costs, morbidity, and mortality of regular cervical cytologic screening

using newer screening technologies compared with conventional Pap smear in women

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participating in screening. Using a Markov model of a cohort of women ages 15 to 85,

incorporating estimates about the natural history of HPV, and investigating one-, two-, and three-

year screening intervals, they reached the following conclusions:

• The cost-effectiveness of either a technology that improves primary screening

sensitivity (e.g., thin-layer cytology) or one that improves rescreening sensitivity

(e.g., computerized rescreening) is directly related to the frequency of screening—

longer intervals result in lower estimates of cost per life year saved.

• Findings were relatively insensitive to assumptions about cervical cancer incidence,

cost of technologies, diagnostic strategies for abnormal screening results, age at onset

of screening, or most of the other variables tested.

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