Innovations In Clinical Neuroscience

NOV-DEC 2017

A peer-reviewed, evidence-based journal for clinicians in the field of neuroscience

Issue link: https://innovationscns.epubxp.com/i/924986

Contents of this Issue

Navigation

Page 33 of 83

34 ICNS INNOVATIONS IN CLINICAL NEUROSCIENCE November-December 2017 • Volume 14 • Number 11–12 O R I G I N A L R E S E A R C H and the ETS criteria make for a more robust finding. Additionally, the ETS categories were created only for identifying items that display statistically significant DIF, which cannot be represented by effect size alone. A description of the ETS DIF used in this analysis can be found in Appendix 2. In DIF analyses, the focal group refers to the group of interest, whereas the reference group refers to the group with which the focal group is being compared. 33 In the current study, all distinct geographical regions except for the United States were chosen as focal groups and the United States was chosen as the reference group. As the PANSS was developed in the United States and initially validated on a United States population sample, the authors chose to compare each country grouping with that of the United States. The Mantel-Haenszel procedure is performed in jMetrik™ and produces effect size computation and ETS DIF item classifications as follows: AA (negligible DIF), BB (moderate DIF), and CC (large DIF) levels. 34 Additional classifications include the following: • AA =negligible DIF • BB+ =moderate DIF favoring the focal group (indicating the item appears more uniformly and reliably scored for the severity level vs. the United States) • BB- =moderate DIF favoring the reference group (indicating the item appears more uniformly and reliably scored for the severity level vs. the comparison region) • CC+ =large DIF favoring the focal group (indicating the item appears more uniformly scored for the severity level vs. the United States) • CC- =large DIF favoring the reference group (indicating the item appears more uniformly and reliably scored for the severity level vs. the comparison region). RESULTS Demographic and clinical data are reported in Table 2 and include subject age, age of onset, sex, and PANSS total scores. The KMO measure of sampling adequacy ranged from 0.95 to 0.99, and Bartlett's test of sphericity was significant (p≤0.001), indicating that a factor analysis was appropriate for these data. Consistent with findings in people with schizophrenia, 1,5,21 we identified the two-factor solution of negative symptoms in our sample (Figure 1). Fit indices for the two models are presented in Table 3. Chi-square difference tests comparing the one-factor and two-factor models found that the two-factor model exhibited a significantly better fit than did the one-factor model (c 2 =68.127, degrees of freedom=1, p≤0.001); therefore, the two-factor model was selected as the final model. The two-factor model shows good model fit (Table 3). 25–27 DIF analysis was performed for items on the PANSS expressive deficit factor and the PANSS experiential deficit factor for 15 geographical regions as compared with the United States. Results are presented in Table 4. All significant differences in chi-square also reported moderate effect sizes, thereby confirming the DIF for all items with moderate (BB) to large (CC) ETS classifications. With respect to the expressive deficit factor, more DIF was observed for items in the expressive deficit factor category than for items in the experiential deficit factor category. Across countries, there were 16 cases of large DIF and 21 cases of moderate DIF for expressive deficit items (out of 60 total item-by-region comparisons), as compared with four cases of large DIF and 10 cases of moderate DIF for experiential deficit. The following regions showed moderate-to-large DIF for all items of the expressive deficit factor: Austria-Germany, Nordic, France, and Poland. Similarly, Austria- Germany, Brazil, and South Africa showed large DIF (CC) for three items of the expressive factor. France and Spain showed large DIF (CC) for N3 Poor Rapport and N6 Lack of Spontaneity and Flow of Conversation as compared with the United States. India was the only country FIGURE 1. Two models of the PANSS negative symptoms factor: 1) a one-factor model; 2) a two-factor model 1 2 TABLE 2. Sample demographic and clinical characteristics of study population TOTAL NUMBER OF SUBJECTS 6,889 Male (%) 4493 (65.22%) Female (%) 2396 (34.78%) AGE Mean 40.12 years SD 12.35 years AGE AT ONSET Mean 25.05 years SD 8.56 years PANSS TOTAL SCORE Mean 83.11 SD 19.09 PANSS POSITIVE SYMPTOM SUBSCALE SCORE Mean 19.49 SD 6.70 PANSS NEGATIVE SYMPTOM SUBSCALE SCORE 7 –44 Mean 22.70 SD 6.93 Range (min–max) 7–48 PANSS NEGATIVE SYMPTOM FACTOR SCORE Mean 21.45 SD 6.98 Range (min–max) 7–48 SD: standard deviation; PANSS: Positive and Negative Syndrome Scale

Articles in this issue

Archives of this issue

view archives of Innovations In Clinical Neuroscience - NOV-DEC 2017