Meta-analysis of the factor structure of the Scale for the Assessment of Negative Symptoms (SANS) and the Scale for the Assessment of Positive Symptoms (SAPS)

Abstract

Introduction

The SAPS and SANS was designed to measure two broad factors, but the majority of factor analyses conducted have found substantially more dimensions. To investigate their structure a meta-analysis was conducted of SAPS and SANS factor analysis.

Method

A total of 42 articles reporting 55 factor analyses were retrieved from database searches (PubMed, PsychINFO) supplemented by searches of references. Reproduced correlations were calculated from retrieved factor analyses and 3 separate meta-analyses were conducted.

Results

The meta-analysis of the SAPS SANS global ratings (k = 34; n = 5219) yielded a 3-factor solution including Positive Symptoms (Hallucinations and Delusions), Negative Symptoms (Affective Flattening, Alogia, Avolition/Apathy, Anhedonia/Asociality and Attentional Impairment), and Disorganization (Positive Formal Thought Disorder and Bizarre Behavior). The item analysis of the SAPS SANS combined (k = 11; n = 3146) found 4 factors, with the Negative Symptoms splitting into Affective Flattening/Alogia and Avolition/Asociality as main difference. The SANS only item analysis (k = 10; n = 2073) identified 3 factors, Affective Flattening, Avolition/Asociality, and Alogia/Inattentiveness. Importantly, our data suggests that the items Inappropriate Affect and Poverty of Content of Speech should be moved from Negative Symptoms to the Disorganization factor. Attentional Impairment shows the highest loading on Negative Symptoms but its inclusion under this dimension is conceptually unclear and it may be better considered as a non-specific domain.

Conclusions

The three factor structure of Positive Symptoms, Negative Symptoms and Disorganization accounted for most of the data. The SAPS SANS global scales are generally valid, but suggestions for a conservative revision of SAPS SANS structure, including supplementary subscales, are presented.