Children's Somatization Inventory: psychometric properties of the revised form (CSI-24)

Abstract

Objective: To conduct a multimethod psychometric evaluation to refine the Children's Somatization Inventory (CSI) and to investigate its dimensionality.

Method: The CSI was administered to 876 pediatric patients with chronic abdominal pain at their initial visit to a pediatric gastroenterology clinic. Tools from three psychometric models identified items that most effectively measured the construct of somatization and examined its dimensionality.

Results: Eleven statistically weak items were identified and removed, creating a 24-item CSI (CSI-24). The CSI-24 showed good psychometrics according to the three measurement models and correlated .99 with the original CSI. The CSI-24 has one dominant general factor but is not strictly unidimensional.

Conclusions: The CSI-24 is a reliable and psychometrically sound refinement of the original CSI. Findings are consistent with the view that somatization has a strong general factor that represents a continuum of symptom reporting, as well as minor components that represent specific symptom clusters in youth with chronic abdominal pain.

Figure 1.

Scree plot of eigenvalues for CSI-24 in the cross-validation sample. The dots show principal component eigenvalues for the CSI-24 in the cross-validation sample. The dashed line is a comparison from a parallel analysis of random numbers in 50,000 simulated data sets with the same number of cases and variables (O’Connor, 2000).

Appendix III.

The figure shows the relation between traditional sum total scores (X) and Rasch measure scores (Y). In the midrange, traditional total scores and Rasch measure scores are closely related, but at the extremes, the nonlinear measure scores stretch to give a better evaluation of extreme scores, with equal-interval measurement even for extreme scores.