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

Three different diagnostic scoring tools have similar accuracy for identifying adults at risk of acute mountain sickness (AMS). One tool, the Clinical Functional Score (CFS), is the simplest to use and consists of asking a single question. (LOE = 2b)

Meier D, Collet TH, Locatelli I, et al. Does this patient have acute mountain sickness? The rational clinical examination systematic review. JAMA 2017;318(18):1810-1819.  [PMID:29136449]

Systematic review

Foundation

Various (meta-analysis)

These investigators searched without language restrictions multiple databases including MEDLINE, EMBASE, and bibliographies of relevant articles for studies reporting epidemiological 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 Questionnaire Score (LLQS) 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 LLQS were the Acute Mountain Sickness-Cerebral score (AMS-C), a visual analog scale score quantifying an overall severity of sickness at altitude (VAS[O]), and a clinical functional score (CFS) composed of a single question: "Overall if you had any symptoms, how did they affect your daily activity?" The CFS 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 2500 m (8200 ft), for every 1000-m increase (3300-ft increase) in altitude, the prevalence of AMS increases by 13% (95% CI 9.5% - 17%). Fourteen studies included head-to-head comparisons of at least 2 different AMS diagnostic tools. Using the LLQS score of 5 or greater as the reference standard, likelihood ratios were similar for the VAS(O), AMS-C, and CFS (positive likelihood ratio range 3.2 - 8.2; and negative likelihood ratio range 0.30 - 0.36). A response of 2 or higher on the single-question CFS (indicating moderate to severe reduction in function) had a pooled sensitivity of 82% and specificity of 67%.