[7 years of annual mass screening for colorectal cancer in office workers--usefulness of 3-day RPHA method].

Immunological fecal occult blood test have been proved to be useful in the mass screening for colorectal cancer. Since 1986, we have started annual mass screening by the use of 3-day RPHA method and medical questionnaire for office workers over 40 yr old. During 7 yr, 261 out of 5386 examinees were testing positive for fecal occult blood, a test positive rate was 4.8% and 12 colorectal cancer (7: early, 5: advanced) were found. Among 12 cases, 10 were detected by positive results of RPHA test and 2 by questionnaires of symptoms or family history. The sensitivity and specificity of this method were calculated at 83.3% and 95.3% respectively. But as for advanced cancers, the sensitivity of this method was 100%. 75% of patients with colorectal cancer were over 55 yr old. The predictive value of positive test (PV) were much more higher in subjects with 2 or 3 times test positive (high risk group: PV = 14.3%) than in subject with only 1 time test positive (low risk group: PV = 0.6%). So it is considered to be reasonable that the high risk group (24% of total test positive) should be immediately undergone further examinations (Ba. enema or colonoscopy), and the low risk group should be undergone re-examinations of 3-day RPHA method. By this system, almost 50% of further examinations will be reduced. In conclusion, 3-day RPHA method with this further examination system is reasonable and efficient for screening of colorectal cancer in office workers, considering the high reliability in cancer detection and decreased further examinations.