[Occult blood screening for colorectal cancer]

Because of the recent increase in the incidence of colorectal cancer in Japan, attempts were made to find an effective method for screening asymptomatic patients with this cancer. In current mass screening, guaiac-impregnated slides such as the Shionogi and Hemoccult types are widely used. A screening system consisting of examination with Shionogi B slides for 3 consecutive days under mild restricted diet and a medical questionnaire, followed by re-examination under a restricted diet for persons showing a partially positive result is accepted as the most reliable screening method. As these slide tests are based on peroxidase-like activity in hemoglobin, dietary fiber, meat, peroxidase-containing foods and drugs influence the sensitivity and specificity of the test. Recently, immunological fecal occult blood tests with high sensitivity and specificity such as RPHA or Feca-EIA have been developed. We have evaluated the RPHA method and compared it with the Shionogi B slide. The positive rate of the RPHA method was rather lower than that of the Shionogi test and the detection rate of Colorectal cancer was equivalent to that of Shionogi. We are now applying the RPHA method to mass screening, and the Feca-EIA Test is also under consideration for practical use.