Assessment of the discriminant analysis concerning the prognostic factors in patients with differentiated thyroid cancer

We reported the result of our discriminant analysis concerning prognostic factors in differentiated thyroid cancer, which based on 134 cases obtained from three hospitals. The sensitivity, specificity and false-negative rate were 59%, 61% and 22%, respectively. When these values were estimated individually in each hospital, the figures were better than those obtained from a whole group of patients. The purpose of this paper is to assess the reliability of the previous result. Simulation was done to assess the relationship between the number of patients and the ratio of criterion variables. New groups were made from the 134 patients by random sampling. In each group, discriminant analysis was done by using the same nine explanatory variables as in the previous report (age, sex, diameter of tumor, site of tumor, histology, local invasion, lymph node metastasis, operative method and lymph node dissection). The results revealed that sensitivity was relatively stable but specificity and false-negative rate were better in the smaller group of patients. The ratio of criterion variables had an effect on the results. In the higher ratio, sensitivity was higher and the false-negative rate was lower.