Predictive Value of Niacin Skin Sensitivity Test for the Diagnosis of Schizophrenia

Objective: To investigate niacin sensitivity in schizophrenia patients, meeting DSM-5 criteria for schizophrenia, as well as to healthy controls (HC) in order to examine the accuracy of niacin skin test in these patients. Methods: this was a diagnostic test accuracy study that conducted in 2018, Zanjan, Iran. We applied niacin patches of three concentrations (0.001 M, 0.01 M, and 0.1 M) to the skin of 36 schizophrenia patients, and 33 healthy controls. Flush responses were rated at 10 and 15 min after application. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were reported for each concentration and considered time-scale.  Results: At the rating time point of 10 min, the greatest degree of differentiation in flush responses among schizophrenia and healthy groups occurred at the 0.001 M concentration, with Sensitivity, specificity, PPV, and NPP of 94%, 50%, 51%, and 94% respectively. Considering rating point of 15 min, the greatest degree of differentiation was observed at the 0.01 concentration with accuracy indicators of 52%, 92%, 79%, and 77%, respectively. Conclusion: Flush responses associated with niacin is impaired among patients with schizophrenia. Therefore, this can be considered as a biological marker of schizophrenia and can be used as complementary diagnostic tool.