Negative Haemoccult^® Test in Malignant and Premalignant Lesions of the Colon

Summary

To date, no published report on a trial has provided sufficiently strong evidence of the accuracy of the Haemoccult^® Test assessed by false-negative error, and validated on the basis of a complete colonoscopy of all patients. Total colonoscopy (up to the cecum) was performed on 534 patients whose stools had been tested for occult blood. The results of the colonoscopy were classified as follows:

• expected continual bleeding (target lesions: carcinoma, polyps ≥ 10 mm)

• intermittant bleeding (polyps < 10 mm, colitis, etc.), and

• no source of bleeding.

Results were regarded as false-negative in patients who were found to have a target lesion (carcinoma, polyp ≥ 10 mm) following a negative Haemoccult^® test. Apart from positive and negative prognostic values, sensitivity and specificity were taken into account as characteristics for the quality of the test. Following a positive Haemoccult^® test result 46 of the 534 patients were found to have polyps ≥ 10 mm and 22 carcinomas; following negative Haemoccult^® test results 31 patients were found to have polyps measuring ≥ 10 mm in diameter and 2 carcinomas. On the basis of the chosen classification a false-negative Haemoccult^® result was established in 8.6 % and a false-positive result in 4.3 %. The Haemoccult^® test showed a sensitivity of 67 % and a specificity of 93 % in patients with target lesions or patients without a source of bleeding.

Key words:

Haemoccult screening - False-negative error - Complete colonoscopy