57Co-labelled bleomycin scintigraphy for the detection of lung cancer: a prospective study.

The sensitivity and specificity of scanning with 57Co-labelled bleomycin for the diagnosis of lung cancer were determined from a prospective study involving a large group of patients with an abnormal chest roentgenogram. A semi-quantitative analysis of the scintigram was obtained by defining an index in terms of the excess isotope uptake within the tumour. Malignant pulmonary lesions were found in 121/175 patients and 113 had a positive scan. Benign pulmonary disorders were found in 54 patients, 45 of whom had a negative scan. The sensitivity and specificity were therefore 93% and 83% respectively. Bayes' theorem was then used to determine the predictive value of this test, either positive or negative, when the prevalence of disease varied from 10 to 90%. A receiver operating characteristic curve permits the choice of an appropriate value of the tumour uptake index to minimize the false positive fraction without classifying too many true positives as false negatives.