Abstract

Introduction

Schizophrenia is a heterogeneous disorder with a wide range of symptoms. This extensive clinical variability poses a challenge for establishing accurate diagnosis and assessing treatment response. The Positive and Negative Syndrome Scale (PANSS) is one of the most widely used instruments to evaluate psychotic symptoms. It is composed of 30 items divided into three subscales - Positive Symptoms, Negative Symptoms, and General Psychopathology - developed to assess the severity of symptoms and measure general psychopathology and drug-related changes.¹1. Kay SR, Fiszbein A, Opler LA. The positive and negative syndrome scale (PANSS) for schizophrenia. Schizophr Bull. 1987;13:261-76.

The PANSS has become an important instrument in schizophrenia research. It is one of the instruments most frequently used to assess efficacy of antipsychotic drugs, based on variation of its total score over time.²2. Kinon BJ, Chen L, Ascher-Svanum H, Stauffer VL, Kollack-Walker S, Sniadecki JL, et al. Predicting response to atypical antipsychotics based on early response in the treatment of schizophrenia. Schizophrenia Res. 2008;102:230-40. It has been validated in several languages and used in the majority of the studies of new drugs for schizophrenia.

The PANSS Study Group successfully validated a model composed by five dimensions.³3. White L, Harvey PD, Opler L, Lindenmayer JP. Empirical assessment of the factorial structure of clinical symptoms in schizophrenia. A multisite, multimodel evaluation of the factorial structure of the Positive and Negative Syndrome Scale. The PANSS Study Group. Psychopathology. 1997;30:263-74. This five-factor model was the most replicated model across studies in the last decade.⁴4. Wallwork RS, Fortgang R, Hashimoto R, Weinberger DR, Dickinson D. Searching for a consensus five-factor model of the Positive and Negative Syndrome Scale for schizophrenia. Schizophr Res. 2012;137:246-50.

For use in Brazil, PANSS was translated into Brazilian Portuguese by means of a standard cross-cultural adaptation process, and its inter-rater reliability was evaluated.⁵5. Chaves AC, Shirakawa I. Escala das síndromes negativa e positiva - PANSS e seu uso no Brasil. Rev Psiquiatr Clin (São Paulo). 1998;25:337-43.,⁶6. Vessoni ALN. Adaptação e estudo da confiabilidade da escala de avaliação das síndromes positiva e negativa para a esquizofrenia no Brasil. São Paulo: Universidade Federal de São Paulo; 1993. Although the PANSS has been widely used in the country, there have been no formal studies validating the scale.

The aim of this study was to investigate whether the factor structure of the Brazilian version of the PANSS converges with the original version and with versions validated for use in other countries/populations, and thus, to generate validity data for the scale in Brazil.

Methods

The sample comprised 292 individuals with a diagnosis of schizophrenia recruited from three different centers: 156 outpatients from the Schizophrenia Program (PROESQ) at Universidade Federal de São Paulo (UNIFESP), Brazil; 93 patients recently discharged from Hospital Luzia de Pinho Melo; and 43 first-episode patients from Santa Casa de Misericórdia de São Paulo, Brazil.

The inclusion criteria were a diagnosis of schizophrenia, as defined by the DSM-IV; age between 12 and 65 years; and absence of severe intellectual disability assessed by family report.

Overall, 191 participants (65.4% of the sample) were men, and the mean ± SD age was 33.64±11.07 years (range, 15-63 years). The mean age at illness onset was 23.10±7.43 years (range, 12-54 years) and mean duration of illness was 10.70±9.67 years (range, 0-43 years). All patients were receiving antipsychotics. The mean Global Assessment of Functioning score was 51.82±14.28, and most of the subjects were “moderately ill” (39.7%) according to the Clinical Global Impression Severity scale (3.57±1.12).

Modules A, B, C, D and E of the Structured Clinical Interview for DSM-IV Axis I Disorders were used for diagnosis and the PANSS was administered to assess psychopathology. Eight experienced psychiatrists were trained in both instruments through regular meetings and clinical supervision.

The factor structure of the PANSS was fitted in a six-factor model by principal component analysis (PCA), with eigenvalues higher than one being retained for factor extraction. Equamax rotation was used as in previous studies with PANSS.⁷7. Fresan A, De la Fuente-Sandoval C, Loyzaga C, Garcia-Anaya M, Meyenberg N, Nicolini H, et al. A forced five-dimensional factor analysis and concurrent validity of the Positive and Negative Syndrome Scale in Mexican schizophrenic patients. Schizophr Res. 2005;72:123-9.,⁸8. Levine SZ, Rabinowitz J. Revisiting the 5 dimensions of the positive and negative syndrome scale. J Clin Psychopharmacol. 2007;27:431-6. Factor loadings of 0.5 or higher were considered in the interpretation of the factors. The internal consistency of each factor was determined by Cronbach's alpha.

Results

The mean ± SD (range) scores obtained were as follows: total PANSS, 64.30±17.37 (31-124); Positive subscale, 13.59±4.70 (7-33); Negative subscale, 18.49±6.33 (7-43); and General Psychopathology, 32.19±9.37 (16-76).

The PCA suggested six factors by the eigenvalue-one criterion. Five of these explained most of the variance and had acceptable internal consistency (> 0.70). The motor factor presented a Cronbach's alpha of 0.404 and explained a small proportion of the variance, suggesting factor inconsistence. Results of the rotated principal component matrix with five and six factor loadings accounted for 58.44 and 61.99% of the total variance, respectively (Table 1).

Regarding sampling adequacy, the Kaiser-Meyer-Olkin test value of 0.873 and the Bartlett test (chi-square = 4339.882, p < 0.001) indicated that the data were highly suitable for factor extraction.

The items “preoccupation” (G15) and “active social avoidance” (G16) were not related to any particular factor in the six-factor model. These items, together with “somatic concerns” (G1) and “lack of judgment and insight” (G12), had insignificant values in the five-factor model.

Discussion

We evaluated the factor structure of the Brazilian version of the PANSS and found a five-factor model similar to those previously described in the literature: positive, negative, disorganization/cognition, excitement and depression/anxiety.

Some previous studies found different number of factors. In the first factor structure study of the PANSS, Kay & Sevy⁹9. Kay SR, Sevy S. Pyramidical model of schizophrenia. Schizophr Bull. 1990;16:537-45. found four factors (negative, positive, excited, and depressive) in an American population. Most recent studies found five to seven factors.¹⁰10. Emsley R1, Rabinowitz J, Torreman M, RIS-INT-35 Early Psychosis Global Working Group. The factor structure for the Positive and Negative Syndrome Scale (PANSS) in recent-onset psychosis. Schizophr Res. 2003;61:47-57.

11. Jiang J, Sim K, Lee J. Validated five-factor model of positive and negative syndrome scale for schizophrenia in Chinese population. Schizophr Res. 2013;143:38-43.-¹²12. Van den Oord EJ, Rujescu D, Robles JR, Giegling I, Birrell C, Bukszar J, et al. Factor structure and external validity of the PANSS revisited. Schizophr Res. 2006;82:213-23. Our model accounted for 58.44% of the total variance; this is very similar to previous results, which ranged from 53.4 to 59.83%.⁷7. Fresan A, De la Fuente-Sandoval C, Loyzaga C, Garcia-Anaya M, Meyenberg N, Nicolini H, et al. A forced five-dimensional factor analysis and concurrent validity of the Positive and Negative Syndrome Scale in Mexican schizophrenic patients. Schizophr Res. 2005;72:123-9.,¹⁰10. Emsley R1, Rabinowitz J, Torreman M, RIS-INT-35 Early Psychosis Global Working Group. The factor structure for the Positive and Negative Syndrome Scale (PANSS) in recent-onset psychosis. Schizophr Res. 2003;61:47-57. As in other studies, the internal consistency we obtained was good (> 0.8) for the negative and disorganized factors, and acceptable (> 0.7) for the remaining factors.¹⁰10. Emsley R1, Rabinowitz J, Torreman M, RIS-INT-35 Early Psychosis Global Working Group. The factor structure for the Positive and Negative Syndrome Scale (PANSS) in recent-onset psychosis. Schizophr Res. 2003;61:47-57.,¹³13. Kim JH, Kim SY, Lee J, Oh KJ, Kim YB, Cho ZH. Evaluation of the factor structure of symptoms in patients with schizophrenia. Psychiatry Res. 2012;197:285-9.

Regarding the composition of individual factors, the negative factor accounted for the greatest individual contribution to variance in the final model (27.97%).⁷7. Fresan A, De la Fuente-Sandoval C, Loyzaga C, Garcia-Anaya M, Meyenberg N, Nicolini H, et al. A forced five-dimensional factor analysis and concurrent validity of the Positive and Negative Syndrome Scale in Mexican schizophrenic patients. Schizophr Res. 2005;72:123-9. The second most robust factor was the “disorganization/cognitive” (11.75%). The item “Mannerisms” appeared previously in the motor dimension of the six-factor model. However, this item fit better when it was moved to the disorganization/cognitive factor in the final five-factor forced model. Fresan et al.⁷7. Fresan A, De la Fuente-Sandoval C, Loyzaga C, Garcia-Anaya M, Meyenberg N, Nicolini H, et al. A forced five-dimensional factor analysis and concurrent validity of the Positive and Negative Syndrome Scale in Mexican schizophrenic patients. Schizophr Res. 2005;72:123-9. highlighted this interface between cognitive and motor components, with the item “Mannerisms” having the highest loading in the Cognitive factor.

The Excitement factor was composed of the same items noted in the study performed by Wallwork et al.⁴4. Wallwork RS, Fortgang R, Hashimoto R, Weinberger DR, Dickinson D. Searching for a consensus five-factor model of the Positive and Negative Syndrome Scale for schizophrenia. Schizophr Res. 2012;137:246-50. of a consensus factor structure of the PANSS. The positive, depression/anxiety, and disorganization/cognition factors were similar to previous studies.⁷7. Fresan A, De la Fuente-Sandoval C, Loyzaga C, Garcia-Anaya M, Meyenberg N, Nicolini H, et al. A forced five-dimensional factor analysis and concurrent validity of the Positive and Negative Syndrome Scale in Mexican schizophrenic patients. Schizophr Res. 2005;72:123-9.,⁸8. Levine SZ, Rabinowitz J. Revisiting the 5 dimensions of the positive and negative syndrome scale. J Clin Psychopharmacol. 2007;27:431-6.,¹⁰10. Emsley R1, Rabinowitz J, Torreman M, RIS-INT-35 Early Psychosis Global Working Group. The factor structure for the Positive and Negative Syndrome Scale (PANSS) in recent-onset psychosis. Schizophr Res. 2003;61:47-57.,¹²12. Van den Oord EJ, Rujescu D, Robles JR, Giegling I, Birrell C, Bukszar J, et al. Factor structure and external validity of the PANSS revisited. Schizophr Res. 2006;82:213-23.,¹³13. Kim JH, Kim SY, Lee J, Oh KJ, Kim YB, Cho ZH. Evaluation of the factor structure of symptoms in patients with schizophrenia. Psychiatry Res. 2012;197:285-9.

Regarding the sixth factor found and not included in the final model, Emsley et al.¹⁰10. Emsley R1, Rabinowitz J, Torreman M, RIS-INT-35 Early Psychosis Global Working Group. The factor structure for the Positive and Negative Syndrome Scale (PANSS) in recent-onset psychosis. Schizophr Res. 2003;61:47-57. performed a study of the PANSS factor structure in recent-onset psychosis. They suggested that the five-factor model did not suffice to show the structure of the PANSS, because a seven-factor model emerged in the exploratory phase of their study with a last factor named “motor.” We found similar results in our model, and a possible explanation for this might be the presence in our sample of some first-episode patients (14.72%), who can be more susceptible to the effect of antipsychotics.¹⁴14. Honer WG, Kopala LC, Rabinowitz J. Extrapyramidal symptoms and signs in first-episode, antipsychotic exposed and non-exposed patients with schizophrenia or related psychotic illness. J Psychopharmacol. 2005;19:277-85. Pappa & Dazzan,¹⁵15. Pappa S, Dazzan P. Spontaneous movement disorders in antipsychotic-naive patients with first-episode psychoses: a systematic review. Psychol Med. 2009;39:1065-76. in a systematic review, alternatively suggested that, although dyskinesia and Parkinsonism can be induced by antipsychotics, in drug-naïve individuals they could also be the result of neurologic dysfunction related to the pathogenesis underlying the illness. Either way, first-episode patients could be more vulnerable to motor symptoms, which may have biased previous studies.

Some PANSS items were not related to any factor. The item “preoccupation” (G15) has some limitation in clinical use, because it aims to assess autistic, egocentric concerns; however, it can be understood as anxiety- or depression-related concern. “Active social avoidance” (G16) is frequently on the negative factor,⁴4. Wallwork RS, Fortgang R, Hashimoto R, Weinberger DR, Dickinson D. Searching for a consensus five-factor model of the Positive and Negative Syndrome Scale for schizophrenia. Schizophr Res. 2012;137:246-50. but was not related to any factor in our study. The item “somatic concern” (G1) was related to the motor factor in our six-factor model; however, it could not be considered a good discriminant item, as it is normally correlated with the depression factor, in most of the articles found in the literature.⁴4. Wallwork RS, Fortgang R, Hashimoto R, Weinberger DR, Dickinson D. Searching for a consensus five-factor model of the Positive and Negative Syndrome Scale for schizophrenia. Schizophr Res. 2012;137:246-50. These items might require revisiting to remain in the scale, because they may not be useful for clinical practice or even for research purposes. This does not seem to be a problem specific to the Brazilian version, but rather an issue with the PANSS itself.

Finally, these results should be interpreted in light of some limitations. Although several methods could be used, we chose factor analysis (based on PCA method) because it was the most widely used technique for analysis of the factor structure of PANSS in previous studies, allowing us to compare our findings to those obtained in other countries/populations and generate convergent validation. Our sample was composed of individuals recruited from three different centers, from all stages of the disorder, under various antipsychotic treatment regimens, and assessed by different psychiatrists, which resembles the clinical reality of schizophrenic patients and reinforces the strength and validity of the current Brazilian version.

The final five-factor model of the Brazilian version of the PANSS presented a performance very similar to the original English version and to those in several other languages, suggesting convergent validity. PANSS is one of the most important primary outcome measures used to evaluate treatment efficacy in psychiatry, and this study shows, for the first time, that its Brazilian version is valid.

Acknowledgements

This work was supported by Fundação de Amparo è Pesquisa do Estado de São Paulo/Conselho Nacional de Desenvolvimento Científico e Tecnológico (FAPESP/CNPq - process: 2011/50740-5) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). RAB has received research grants from FAPESP, CNPq, CAPES, Fundação Safra, and Fundação ABADS.

References

Publication Dates

History