Patients with the disease primary biliary cirrhosis suffer from severe bouts of itching, manifested by chronic scratching. In order to evaluate the efficacy of experimental drugs that may relieve the itching, it is necessary to quantify the scratching. A piezoelectric foil cemented to the patient's primary scratching fingernail will transduce mechanical vibrations generated by the scratching into an electrical signal, which is applied to the input of a miniature FM transmitter. After the signal is obtained with an FM receiver, it will be processed by a custom-designed frequency counter, which in turn is interrogated and reset periodically by a personal computer. The study will consist of measurement periods of six to eight hours, both before treatment and after treatment with specific drugs. Each patient will serve as his or her own control.
