Incidence of cytological abnormalities within 24 months of a normal cervical smear in Soweto, South Africa.

BACKGROUND A screening programme for cervical cancer has been implemented in South Africa (SA) with intervals of 10 years after a normal cytological result. There are no studies that evaluate repeat screening at a shorter interval in SA. OBJECTIVES (i) To find the incidence of cytological abnormalities on a repeat test after a report of normal cytology or an inadequate Pap smear; and (ii) to explore the factors associated with an abnormal cytology on repeat testing. METHODS This was a secondary data analysis of a randomised controlled trial of diaphragm, lubricant gel and condoms v. condoms in the prevention of HIV infection. HIV-negative women were recruited between November 2003 and December 2005, with a normal Pap smear at entry. Observation time was from the first Pap smear to the date of the repeat Pap smear. Explanatory variables used were baseline, excepting any new HIV infection. RESULTS The incidence of cytological abnormalities was 6.48% yearly in women with a previously normal Pap smear and 11.71% yearly in women with an inadequate smear result (p=0.03). The incidence of high-grade squamous intra-epithelial lesions (HSILs) was <0.5%. Factors associated with abnormal cytology were a history of ectopic pregnancy (odds ratio (OR) 9.25; confidence interval (CI) 1.78 - 48.02; p=0.01), number of male partners (OR 1.12; CI 1.03 - 1.22; p=0.01), history of vaginal discharge (OR 13.95; CI 1.18 - 164.47; p=0.04), and incident HIV infection (OR 6.56; CI 1.14 - 38.16; p=0.04). CONCLUSION The incidence of HSILs is low in the first 2 years after a normal or inadequate Pap smear, even in a setting with a high prevalence of cytological abnormalities.