Changes in leg length and height during treatment with somatotropin

Knemometry has been used in a short term double blind placebo controlled trial in 13 patients with normal variant short stature receiving treatment with somatropin to assess the power of the change in lower leg velocity at one month to predict the increase in height velocity at six months. Used in this way the method has a positive predictive value and sensitivity of 90% and a negative predictive value and specificity of 50%. Although not a perfect discriminatory test, knemometry is a more reliable and less invasive way of analysing the likely value of a growth promoting treatment than metabolic assays in individual patients. Given the possible future rapid expansion of the use of somatropin in short stature of various aetiologies there is a need for a relatively simple and inexpensive means of evaluating response to treatment.