Clinical Question

How accurate are diagnostic tools in identifying high-altitude travelers at risk of acute mountain sickness (AMS)?

Bottom Line

Three different diagnostic scoring tools have similar accuracy for identifying adults at risk of AMS. One tool, the clinical functional score, is the simplest to use and consists of asking a single question. (Level of Evidence = 2b)

Synopsis

These investigators searched without language restrictions in multiple databases, including Medline and Embase, and bibliographies of relevant articles for studies reporting epidemiologic data, evaluations, and comparisons of diagnostic procedures or instruments for AMS. Two investigators independently evaluated potential studies for inclusion criteria and methodologic quality using a standard risk-of-bias scoring tool. Disagreements were resolved by consensus agreement with a third reviewer. The Lake Louise scoring system is the accepted reference standard for diagnosing AMS, with a score of 5 or higher indicating severe AMS and a corresponding high risk of developing life-threatening high-altitude cerebral edema. The three instruments that could be compared with the Lake Louise scoring system were the AMS cerebral score, a visual analog scale score quantifying an overall severity of sickness at altitude, and a clinical functional score composed of a single question: “Overall if you had any symptoms, how did they affect your daily activity?” The clinical functional score is scored on an ordinal scale of 0 to 3, indicating none, mild, moderate, and severe (bed rest) reduction in function.

A total of 91 articles (N = 66,944 patients) evaluated the prevalence of AMS, reporting that above 2,500 m (8,200 ft), for every 1,000-m increase (3,300-ft increase) in altitude, the prevalence of AMS increases by 13% (95% confidence interval, 9.5% to 17%). Fourteen studies included head-to-head comparisons of at least two different AMS diagnostic tools. Using the Lake Louise scoring system score of 5 or greater as the reference standard, likelihood ratios were similar for the visual analog scale score, AMS cerebral score, and clinical functional score (positive likelihood ratio range = 3.2 to 8.2; negative likelihood ratio range = 0.30 to 0.36). A response of 2 or higher on the single-question clinical functional score (indicating moderate to severe reduction in function) had a pooled sensitivity of 82% and specificity of 67%.

Study design: Systematic review

Funding source: Foundation

Setting: Various (meta-analysis)

Reference:MeierDColletTHLocatelliIet alDoes this patient have acute mountain sickness? The rational clinical examination systematic review. JAMA2017;318(18):1810–1819.