Sensitivity and specificity of screening cutaneous pre-malignant and malignant lesions

Abstract

The incidence of melanoma is increasing worldwide, prevalence of malignant epithelial tumors is high and early diagnosis reduces significantly the morbi-mortality of these diseases. The purpose of the study is to estimate the prevalence of pre-malignant and malignant skin lesions and to determine the sensitivity and specificity of screening tests. A cross-sectional population-based study was carried out using 48 census tracts randomly selected from urban zone of southern, Brazil. A total of 2,112 dwellings were visited and 1,292 individuals aged 50 years or more were interviewed. The questionnaire consisted of specific questions about new skin lesions in the last six months and/or the presence of lesions on exposed areas. Those who answered affirmatively were referred to the university's outpatient clinic for medical skin examination (gold standard). For assessing specificity the same doctors investigated a sub-sample of those who replied negatively to the questionnaire. The prevalence of pre-malignant and malignant skin lesions was 20.7%. The screening sensitivity was 20.1%, specificity 86.9%, positive predictive value 29%, negative predictive value 80.4%, and accuracy 72.9%. Using different cut-off points, the maximum sensitivity value was 38.8% and specificity remained almost the same. The study showed a high prevalence of skin lesions both pre-malignant and malignant in adults. Skin lesion screening revealed low sensitivity and unsatisfactory specificity, regardless the cut-off points set.