Evaluation of the Balance Error Scoring System (BESS) in the Diagnosis of Acute Mountain Sickness at 4380 m

Abstract

Ascent to altitude is associated with a decrease in balance; however, the effect of acute mountain sickness (AMS) status on balance is variable depending on the test used and the altitude at which the test is performed. Here, we report preliminary findings on the relationship between the balance error scoring system (BESS) and AMS at the 2010 Janai Purnima festival at Gosainkunda, Nepal (4380 m). All subjects (n=37) completed a shortened BESS test (mBESS) while a subset completed the full BESS test (n=27). Pulse oximetry was used to measure heart rate and oxygen saturation, and blood pressure was measured by sphygmomanometer. Balance test scores (BESS and mBESS) and physiological measurements were compared between groups with AMS (AMS⁺) and without AMS (AMS⁻). Receiver-operator characteristic (ROC) curves were used to compare the abilities of the BESS and mBESS tests to correctly identify the AMS status of subjects. The AMS⁺ group had significantly higher Lake Louise scores than the AMS⁻ group (mean=4.0 (standard deviation=1.3) vs. 0.3 (0.6), p<0.001). The AMS⁺ group also scored significantly higher on both the mBESS (6.6 (3.5) vs. 2.7 (1.7) errors, p=0.018) and the BESS tests (19.2 (8.8) vs. 10.4 (6.0) errors, p=0.001) compared to the AMS⁻ group, indicating inferior balance in the AMS⁺ group. The area under the ROC curve was significantly greater for the BESS test (0.895) compared to the mBESS test (0.690, p=0.02), implying that the full BESS test more accurately identified a subject's AMS status. Additional studies are needed to determine if BESS could be a useful adjunct to the clinical diagnosis of AMS.