[Validation of a predictive index of neoplasia in unexplained weight loss].

Background: Involuntary weight loss (IWL) is associated with a bad prognosis. A causal diagnosis is difficult and the priority is to identify those patients at risk of a serious underlying disease, such as malignant neoplasia.

Objective: External validation of a prognostic index of neoplasia in patients with IWL.

Methods: Patients referred for IWL from 2005 to 2014 to the Department of Internal Medicine, of a specialty care hospital in Mexico City were studied. Al of them underwent an evaluation consisting of medical history, physical examination and basic laboratory studies, those patients without an apparent cause of IWL, were included. A probability of neoplasia according to Hernández prognostic index was calculated. Complementary diagnostic studies were performed until a causal diagnosis was reached, or the cases were classified as “unknown cause”, if the etiology was not possible to find after one year of follow-up. A binarian logistic model was constructed with five variables age, leucocyte count, albumin, lactic dehydrogenase and alkaline phosphatase levels, and a prediction rule was developed.

Results: 130 Patients were included and 45 of them (30%) had a neoplastic cause of IWL. The prediction rule according to Hernández criteria, correctly classified 65% of the patients (sensitivity 29%, Specificity 85%, positive predictive value 50% and negative predictive value 69%). When the original index was modified in two categories (high and low probability), it showed a sensitivity of 84.4% and a negative predictive value of 85.7%.

Conclusion: The Hernández index has a limited value as a screening tool.