A volumetric biochemical niacin flush-based index that noninvasively detects fatty acid deficiency in schizophrenia

(1) It is possible to investigate aspects of phospholipid-related signal transduction in humans noninvasively using the niacin skin flush test. (2) Patients with schizophrenia have previously been reported to show a reduced flushing response. (3) The aim of this study was to devise a comprehensive index of cutaneous response to the niacin test, incorporating aqueous methyl nicotinate concentration and time, and to test this index in schizophrenia. (4) A discrete approximation to a continuous volumetric index, which we have named the volumetric niacin response (VNR), was devised. Its value was measured in 27 patients with DSM-IV schizophrenia and 26 age- and sex-matched normal controls. (5) The mean value of the VNR in the patients with schizophrenia (16.26) was significantly smaller than that of 26.77 in the normal controls (P<.0004). (6) With a threshold value for the VNR of 21, the test differentiated well between schizophrenia and normal controls (P=.002) with a sensitivity of 78% and a specificity of 65%. (7) The present results confirm that the flushing response is reduced in schizophrenia, and show that calculation of the VNR is an effective means of allowing the total response in different patients or patient groups to be readily compared.