Context Clinicians must be able to diagnose myasthenia gravis, since delays
in establishing the diagnosis may put patients at risk for complications from
this treatable disease.
Objective To determine if items in the history and examination or results of simple
tests change the likelihood of myasthenia gravis as a diagnosis.
Data Sources MEDLINE search of English-language articles (January 1966-January 2005)
using the terms myasthenia gravis, diagnosis, and test, and a search of bibliographies
of retrieved articles.
Study Selection Studies evaluating a particular symptom or sign in patients both with
and without myasthenia gravis. Of 640 articles retrieved, 33 were eligible
for review. Of these, 15 met inclusion criteria and form the basis of this
Data Extraction Two authors independently reviewed each study to determine eligibility,
abstracted data using a standardized instrument, and classified study quality
using previously published criteria.
Data Synthesis A history of “speech becoming unintelligible during prolonged
speaking” and the presence of the peek sign increase the likelihood
of myasthenia gravis (likelihood ratio [LR], 4.5; 95% confidence interval
[CI], 1.2-17.0 and LR, 30.0; 95% CI, 3.2-278.0, respectively). Their absence
does not significantly reduce the likelihood of myasthenia gravis. The identified
studies only assessed 1 other historical feature and sign each (“food
remaining in the mouth after swallowing” and quiver eye movements, respectively),
and neither of these significantly changes the likelihood of myasthenia. The
ice test is useful when the response is abnormal (summary positive LR, 24.0;
95% CI, 8.5-67.0) and diminishes the likelihood of myasthenia gravis when
the response is normal (summary negative LR, 0.16; 95% CI, 0.09-0.27). A positive
response to an anticholinesterase medication (mainly edrophonium test) increases
the probability of a diagnosis of myasthenia gravis (summary positive LR,
15.0; 95% CI, 7.5-31.0), and a negative response reduces the diagnostic probability
of myasthenia (summary negative LR, 0.11; 95% CI, 0.06-0.21). An abnormal
sleep test result is useful in confirming the diagnosis (LR, 53.0; 95% CI,
3.4-832.0). The rest and sleep tests make the probability of myasthenia unlikely
when results are normal (LR, 0.52; 95% CI, 0.29-0.95 and LR, 0.01; 95% CI,
Conclusions Items in the history and physical examination along with results of
certain simple tests performed in the office (ice test, sleep test, and edrophonium
test) are useful in predicting the likelihood of myasthenia gravis. These
results must be interpreted with caution, however, given the high prevalence
of disease in the populations reported in clinical studies. This review is
limited by the small number of signs and symptoms scientifically studied and
reported in the literature. Future studies evaluating the value of common
historical features and easy maneuvers commonly known and practiced by experts
in the clinical diagnosis of myasthenia are needed.