A systematic review including 15 studies with a total of 896 subjects (358 myasthenia gravis patients) was abstracted in DARE. All of the included studies were diagnostic case-control studies. The positive LR reported for 'food in mouth after swallowing' was 13.0 (95% CI: 0.85, 212.0) and the negative LR was 0.70 (95% CI: 0.58, 0.84). For 'unintelligible speech after prolonged speaking', the reported positive and negative LRs were 4.5 (95% CI: 1.2 to 17.0) and 0.61 (95% CI: 0.46 to 0.80), respectively. The positive LR reported for the peek sign was 30.0 (95% CI: 3.2, 278.0) and the negative LR was 0.88 (95% CI: 0.76, 1.0). For the sleep test, the reported positive and negative LRs were 53.0 (95% CI: 3.4 to 832.0) and 0.01 (95% CI: 0.00 to 0.16), respectively. The pooled positive and negative LRs for the ice test were 24.0 (95% CI: 8.5 to 67.0) and 0.16 (95% CI: 0.09 to 0.27), and the pooled positive and negative LRs for the anticholinesterase test were 15.0 (95% CI: 7.5 to 31.0) and 0.11 (95% CI: 0.06 to 0.21), respectively.
Explanation of tests and signs: Sleep test: Resolution of ptosis or ophthalmoparesis immediately after a 30-minute period of sleep; the reappearance of the myasthenic signs over the next 30 seconds to 5 minutes adds further confirmation. Ice test: Two or more millimeters of improvement in ptosis after 2 minutes of ice application on the ptotic eyelid is considered a positive ice test result. Peek sign: On lid closure to command, the orbicularis muscle initially may achieve lid apposition; however, as the patient continues to try to keep the eyes forcefully closed over a minute, the orbicularis oculi fatigues, and sometimes the lids separate to show a rim of sclera, with the patient appearing to "peek" at the examiner.
Comment: The quality of evidence is downgraded by limitations in study quality and by indirectness.