Validity, Reliability, and Diagnostic Accuracy of the Respiratory Distress Observation Scale for Assessment of Dyspnea in Adult Palliative Care Patients.

BACKGROUND: The prevalence and severity of dyspnea increase at the end of life. Many of these patients have difficulty in reporting their symptoms. Accurate surrogate measures are needed for appropriate assessment and treatment. The Respiratory Distress Observation Scale (RDOS) is proposed as a possible scale although more external validation is needed. We set out to validate the RDOS in the context of palliative care patients near the end of life.

MEASURES: We prospectively studied 122 palliative care patients in a tertiary hospital in Singapore. Prior RDOS training was done using a standardized instructional video. Dyspnea was assessed by RDOS, Dyspnea Numerical Rating Scale, and Dyspnea Categorical Scale. Pain was assessed by Pain Numerical Rating Scale. We measured RDOS inter-rater reliability, convergent validity, and divergent validity. We used area under receiver operating characteristics curve (AUC) analysis to examine the discriminant properties of RDOS using dyspnea self-report as benchmark.

RESULTS: RDOS had good inter-rater reliability with an intraclass correlation of 0.947 (95% CI 0.919-0.976). It showed moderate-to-strong correlation with Dyspnea Numerical Rating Scale (r = 0.702) and Dyspnea Categorical Scale (r = 0.677) and negligible correlation to Pain Numerical Rating Scale (r = 0.080). It showed good discriminant properties of identifying patients with moderate and severe dyspnea with an AUC of 0.874 (95% CI 0.812-0.936). RDOS ≥ 4 predicted patients with moderate and severe dyspnea with a sensitivity of 76.6%, specificity of 86.2%, positive predictive value of 86.0%, and negative predictive value of 76.9%.

CONCLUSIONS: The RDOS shows promise and clinical utility as an observational dyspnea assessment tool. Further studies in uncommunicative patients are needed to determine clinical usefulness and generalizability of results.