Evaluation of a screening test for the early detection of oral cancer and precancer.

The purpose of this study was to establish the sensitivity and specificity of a clinical examination for the detection of early oral cancer and precancer. A screening programme was conducted over a period of one year and 2027 subjects aged 40 years and over were examined. Screening took place at two sites; opportunistically in outpatient departments at a dental hospital and by postal invitation at an inner city medical practice. The screening procedure included a questionnaire on habits and an oral examination by two independent dentists. The first examining dentist (the screener) was either a general dental practitioner, a community dental officer or a junior hospital dentist. There were 24 dentists in the screener group. A second single examining dentist (a specialist) provided the definitive diagnosis, or 'gold standard', with which the screeners' results were compared. A screen was defined as positive if a white patch, a red patch, or an ulcer of longer than two weeks duration was detected. Each subject was categorised as either positive or negative by both the screener and the specialist. The screener and specialist were unaware of each other's findings. The prevalence of disease according to the specialist was 2.7 per cent. The results for all 24 screeners were pooled and gave an overall sensitivity of 0.74 (95 per cent CI, 0.62 to 0.86), specificity of 0.99 (95 per cent CI, 0.985-0.994) and positive and negative predictive values of 0.67 and 0.99 respectively.