Bronchial carcinoma. IV. A methodological evaluation of the vitagram index for measurement of quality of survival

Abstract

The validity of the Carlens Vitagram Index was tested by using the result of therapy in 48 patients with bronchial carcinoma in advanced disease, 54 patients with localized disease and 34 deceased treated surgically. The Carlens Vitagram Index, which is additional and composed of six items, was correlated to a set of additive indexes including the same items but other item weights, which were chosen with non-controversial pre-specified restrictions. The lowest correlation achieved was an indicator of the lowest degree of consistency that could be attributed to the Carlens Index given. The definition of the index was operationalized so far that each item in the set of six items included in the index was regarded as valid, and it was also considered reasonable that only these six items should be included; that each item had a weight; that the index was obtained as a product (weight x item value) sum and that the pre-specified conditions were accepted. By using restrictive conditions the lowest correlation between the index giving the lowest correlation and the Carlens Index for the 48 patients with localized disease was 0.98, for the 54 patients with localized disease 0.91 and for the surgically treated ones 0.83. In addition to the total index, the average index per month was also studied and the corresponding correlations were 0.96, 0.86 and 0.81 respectively. The Carlens Index and its application per month was found to have good validity for inoperable patients and acceptable validity for surgically treated patients. The Carlens Index was shown to be robust and there is reason to believe that it lies close to the optimal index.