Objective evaluation of scintigraphic diagnosis of bone metastasis.

Using bone scintigraphs (B.S.) from neoplasic patients, a quantitative analysis of the relation existing between objective scintigraphic signs and the diagnosis of presence or absence of bone metastases was carried out. In this way, an attempt was made to increase the specificity of the B.S. for this diagnosis. Thus, a group of signs from the B.S. was chosen and an analysis of the frequency of their presence in relation to the diagnosis of bone metastasis was carried out. For each sign, considered as discrete mathematical variables, an index arising from the following expression: Sensitivity - (1 - Specificity) was calculated. In this manner, each scintigraph may be quantified by the addition of the indices which correspond to the signs present in it. The set of possible numerical values was divided into 7 intervals, each of which establishes a different degree of reliability in the diagnosis of bone metastasis. This approach permitted ROC analysis and the formation of the representative curve.