Comparison of VAS and Lake Louise symptom scores for acute mountain sickness (AMS)

Assesing presence and severity of AMS is based on subjective reporting of sensation of symptoms. The Lake Louise symptom scoring system (LLs) uses categorical variables to rate intensity of AMS-related symptoms (headache,gastrointestinaldistress, dizzines,fadigue, sleep quality) on 4 point ordinal scales, the sum off answers being the LLS self-score (range 0-15). Recent publications indicate a potential for a visual analogue scale (VAS) to quantify AMS.We tested the hypothesis whwter overall and single item VAS and LLS scores scale linearly.We asked 14 un -acclimatized male subject (age41:14), mean:SD yr, who spent 2 days at 3647m and 4 days at 4560m to fill out LLS questionaires, with a VAS for each item as well as a VAS for the overall sensation of AMS, twice a day.Even though correlated (r=0,84) the relationship between LLS-o and VAS-o was distorted showing a treshold effect for LLS-o scores below 5 with most VAS-o scores on one sitde of the idwntity line. Similar threshold effects were seen for the LLS-i and VAS-i scores . These findings indicate non linear scaling characteristics that render direct comparison of studies done with either VAS or LLS alone difficult