Neurological soft signs as an endophenotype in an African schizophrenia population - a pilot study

Objective: The use of endophenotypes, such as neurological soft signs (NSS), is advocated as one possible method to elucidate the heterogeneity of schizophrenia. Exploring the associations between NSS and specific illness symptoms has revealed some trends, although results have been conflicting. To date, such studies have been conducted largely on Caucasian populations and our pilot study represents the first attempt to gather such data in a homogenous African population. Method: Fifty-one patients, all of Xhosa ethnicity and participating in a larger schizophrenia genetic study were recruited. NSS were evaluated using a modified Neurological Evaluation Scale. Data were analysed using SPSS with the strength of the overall relationships between NES groups and SANS and SAPS components analyzed by means of canonical correlation analysis. Results: The canonical correlation of SANS domains (excluding asociality) with the NES conceptual groups was 0.53 (SE=0.11, p=0.024) and of the SAPS domains 0.38 (SE=0.13, p=0.943). Conclusion: Our results suggest a correlation between negative symptoms of schizophrenia and the presence of NSS, supporting the recruitment of a larger sample to more comprehensively evaluate a possible role for NSS as an endophenotype in the Xhosa schizophrenia population. Taking into account that NSS evaluations allow for inexpensive, relatively easy-to-do objective evaluations, this method presents us with a valuable research tool that can be used effectively within our under-resourced environment to help inform on the neurobiological substrate of schizophrenia.