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Abstract
Objective To compare the diagnostic accuracy of ice pack test (IPT) and single-fiber EMG (SF-EMG) in patients with suspected ocular myasthenia (OM) presenting with ptosis.
Methods We studied consecutive patients referred for the clinical suspicion of OM. Patients underwent IPT and stimulated SF-EMG on the orbicularis oculi muscle. Receiver operating characteristic curve analysis was performed to determine the accuracy of IPT, SF-EMG, and their combination.
Results We included 155 patients, 102 with OM and 53 with other diagnosis (OD). The IPT had a sensitivity of 86% (95% confidence interval [CI] 79–93) and a specificity of 79% (95% CI 68–90). SF-EMG showed a sensitivity of 94% (95% CI 89–98) and a specificity of 79% (95% CI 68–90). Overall, IPT and SF-EMG showed discordant results in 30 cases, 16 OM and 14 OD. The combination of IPT and SF-EMG, using the positivity of at least one test for OM diagnosis, increased the sensitivity to 98% (95% CI 95–100), reducing the specificity to 66% (95% CI 53–78), whereas using the positivity of both tests, we obtained a sensitivity of 82% (95% CI 75–90) and a specificity of 92% (95% CI 85–99). The negativity of both tests had a 94% (95% CI 87–100) negative predictive value. Comparison of the areas under the curve showed no differences in the diagnostic accuracy of IPT, SF-EMG, and their combinations.
Conclusions IPT and SF-EMG have similar diagnostic accuracy in patients with OM presenting with ptosis. The negativity of both tests strongly suggests another diagnosis.
Classification of evidence This study provides Class I evidence that both the IPT and SF-EMG accurately identify patients with OM.
Glossary
- AChEI=
- acetylcholinesterase inhibitor;
- AChR-ab=
- acetylcholine receptor antibody;
- AUC=
- area under the curve;
- CI=
- confidence interval;
- IPT=
- ice pack test;
- MRD=
- margin reflex distance;
- NPV=
- negative predictive value;
- OD=
- other diagnosis;
- OM=
- ocular myasthenia;
- PPV=
- positive predictive value;
- RNS=
- repetitive nerve stimulation;
- SF-EMG=
- single-fiber EMG
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
Editorial, page 563
Class of Evidence: NPub.org/coe
- Received December 19, 2019.
- Accepted in final form April 14, 2020.
- © 2020 American Academy of Neurology
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