Swan-neck sign of the big toe - association with hypocalcaemia.

The sensitivity and specificity of a new clinical sign of hypocalcaemia were evaluated. The Swan-neck sign, wherein infants with symptomatic hypocalcaemia keep their big toe hyperextended at the metatarsophalangeal joint and flexed at the interphalangeal joint, was looked for in 25 infants presenting with non-febrile seizures, alongside their serum calcium levels. The study showed that the sign had a sensitivity of 63.6% and specificity of 66.6%. (Predictive values of positive and negative tests were 93.3% and 20%, respectively.) This is compared with the standard Trousseau and Chvostek signs.