Inventi Impact: Clinical Research

Inventi:pcr/26050/18

Assigning Clinical Significance and Symptom Severity Using the Zung Scales: Levels of Misclassification Arising from Confusion between Index and Raw Scores

Background. The Zung Self-Rating Depression Scale (SDS) and Self-Rating Anxiety Scale (SAS) are two norm-referenced scales\ncommonly used to identify the presence of depression and anxiety in clinical research. Unfortunately, several researchers have\nmistakenly applied index score criteria to rawscores when assigning clinical significance and symptom severity ratings.This study\nexamined the extent of this problem. Method. 102 papers published over the six-year period from2010 to 2015 were used to establish\ntwo convenience samples of 60 usages of each Zung scale. Results. In those papers where cut-off scores were used (i.e., 45/60\nfor SDS and 40/60 for SAS), up to 51% of SDS and 45% of SAS papers involved the incorrect application of index score criteria\nto raw scores. Inconsistencies were also noted in the severity ranges and cut-off scores used. Conclusions. A large percentage\nof publications involving the Zung SDS and SAS scales are using incorrect criteria for the classification of clinically significant\nsymptoms of depression and anxiety.Themost common error�applying index score criteria to raw scores�produces a substantial\nelevation of the cut-off points for significance. Given the continuing usage of these scales, it is important that these inconsistencies\nbe highlighted and resolved.