Organized versus Spontaneous Pap Smear Screening for Cervical Cancer
Nieminen et al. (1999) compared two different strategies for reducing the incidence of invasive cervical cancer. The organized approach consists of a centralized organization inviting women between 30 and 60 years of age for screening every 5 years by letter. The invitation describes the place, date, and time for taking the screening tests. The spontaneous screening approach consists of women seeking a Pap smear from a gynecologist. Cases were 179 incident cases of invasive cervical cancer treated at the Helsinki University Central Hospital (HUCH). Controls were 1507 women sampled from the Finnish Population Registry who were also residents of the HUCH catchment area. Questionnaires were sent to cases and controls concerning Pap smear history (before diagnosis date of cancer for cases; before corresponding date for controls), sociodemographic characteristics, and other health habits. The odds ratio of invasive cervical cancer among those who participated in the organized screening was 0.38 (CI 0.26-0.56) in terms of unit risk compared to those not having the screening. The odds ratio of invasive cervical cancer among those with any lifetime spontaneous pap smear had an OR value of 0.82 (CI 0. 53-1.26), in terms of unit risk compared to those not having the screening.
Q1. Explain the statistical results for both types of screening.
Q2. What can you conclude regarding the effectiveness of organized Pap smear screening?
Q.3. Discuss the odds ratio for both. How would you explain the odds ratio in lay terms?
Q4. What are some potential confounding variables in the study?
Q.5. What are some of the obstacles to implementing a similar organized screening system for cervical cancer in the United States?