Reliability and Validity of the Standardized Elevated Arm Stress Test in the diagnosis of Neurogenic Thoracic Outlet Syndrome

Objective: We developed a standardized elevated arm stress test (sEAST) meter to standardize patients' posture and measure additional grip and fatigue parameters. In the present prospective cohort study, we aimed to determine the reliability and validity of the sEAST in the diagnosis of neurogenic thoracic outlet syndrome (NTOS).Methods: Patients evaluated for NTOS between October 2018 and February 2020 were included and performed the sEAST. The patients were classified into a proven NTOS group or a symptomatic control group using the reporting standards for NTOS and the outcome of thoracic outlet decompression surgery. Healthy persons were recruited as an asymptomatic control group. The testeretest reliability, area under the receiver operating characteristic curve, and positive and negative predictive values were calculated for each sEAST parameter.Results: A total of 426 patients with suspected NTOS and 147 healthy controls had performed the sEAST. The validity analysis was performed with data from 111 patients with proven NTOS, 94 symptomatic controls, and 147 asymptomatic controls. The reporting standards were inconclusive for 116 patients; 77 patients had been excluded because thoracic outlet decompression surgery had not been performed or was unsuccessful, and 28 because they had arterial or venous thoracic outlet syndrome. The area under the receiver operating characteristic curve for the proven NTOS group compared with the asymptomatic control and symptomatic control groups ranged from 0.59 to 0.77 and 0.54 to 0.63, respectively. The positive predictive value ranged from 46% to 65% and the negative predictive value from 51% to 66%. The testeretest reliability analysis for 80 patients with multiple sEAST measurements showed moderate to good (0.52-0.87) intraclass correlation coefficient values for the duration and grip strength parameters. However, the grip fatigue parameters demonstrated poor (0.46-0.16) intraclass correlation coefficient values.Conclusions: The sEAST showed good testeretest reliability for the duration and grip strength parameters. However, the discriminative value of all sEAST parameters was low for NTOS diagnostics. The good testeretest reliability of the sEAST parameters indicates that they could be valuable outcome measures for comparison in a diagnostic care pathway.