Question
Chvostek sign is considered to be evidence of neuromuscular hyperexcitability, and is seen as a sign of hypocalcemia. However, why is this clinical sign essentially worthless?
Chvostek征被认为是神经肌肉兴奋性增高的表现，并且可见于低钙血症。但是，为什么这个临床体征的价值非常有限？
Answer
25% of healthy individuals (43% between the ages of 20 and 29 years) have a positive Chvostek sign, and 29% of patients with hypocalcemia do not.
25％的健康人会有阳性Chvostek征，而29％低钙血症患者却可能是阴性。所以这个体征的特异性和敏感性都不高。
Reference
Neurology, Vol. 80, no. 11, pg. 1067
Bonus Points
Chvostek征：用手指或硬物扣击耳垂前方面神经处（即腮腺后方）出现面肌抽搐即为阳性。
低钙血症除了会有Chvostek征，还容易出现Trousseau征：：用血压计袖带按常规血压测量方法绑定，充气使袖带压力升至收缩压与舒张压之间，五分钟左右，同侧肢体远端出现手搐搦为阳性。
