Diagnostic accuracy of the Care Dependency Scale

Abstract

This paper reports an investigation of the diagnostic accuracy of the Care Dependency Scale (CDS). Assessment tools can be described in terms of diagnostic accuracy, or the ability to correctly classify subjects into clinically relevant subgroups. Diagnostic accuracy can be determined by several techniques as sensitivity, specificity, receiver operating curve analysis and likelihood ratios. A cross-sectional design was used with data from 237 patients from two studies. Data were collected using a questionnaire consisting of the CDS and the Barthel Index (BI). The CDS is a relatively new instrument and should be validated by comparison against an established gold standard, in this case the BI. Measures to quantify the validity of diagnostic tests, such as sensitivity, specificity, positive and negative predictive values, prevalence and likelihood ratios were calculated. In addition, the receiver operating characteristics (ROC) curve analysis was used to report the test accuracy of the CDS and to determine an appropriate cut-off point for care dependency detection. The prevalence in the sample study was very high (84%). The area under the ROC curve for the CDS was 0.81, which indicates moderate diagnostic accuracy. Patients with a CDS sumscore </=68 (rule-out cut-off point) were classified as care dependent, all others as independent. The determination of the appropriate cut-off point was based on sensitivity (0.85) and positive predictive valued (0.90). The CDS may be used for to estimate care dependency among hospital patients with various conditions.