Evaluation of the nationwide cervical screening programme in Thailand: a case-control study

Abstract

Objectives To evaluate the effectiveness of the Pap smear screening programme in Thailand in the prevention of invasive cervical cancer. Setting Four tertiary hospitals, in two provinces of north-east Thailand. Methods A hospital-based case-control study of women aged 30–64, who were resident in north-east Thailand. A total of 130 women with a diagnosis of invasive cervical cancer were compared with two groups of controls: a) hospital controls, b) hospital patient companions. Information on risk factors for cervical cancer and history of screening by cytology (Pap smear) were collected using a structured interview. Results Eighty percent of control subjects reported having had a Pap test in the past, and some two-thirds within the three years before interview. There was a significant protective effect for multiple (6+) previous screening tests as reported by 20% of controls. When women who had tests less than six months prior to the study were excluded, there was a strong, significant protective effect of the number of tests (for 1–5 tests: OR = 0.45 95% CI = 0.25 to 0.84, and for 6+ tests: OR = 0.29 95% CI = 0.11 to 0.82). Tests carried out 1–2 years and 3+ years before diagnosis were associated with an OR of 0.27 (95% CI = 0.13–0.56) and 0.42 (95% CI = 0.20–0.88), respectively. Conclusions The cervical screening programme in north-east Thailand has achieved excellent coverage and is preventing cervical cancer. Women who have been screened multiple times are at substantially lower risk than those only screened a few times suggesting that the quality of the screening could be improved.