<prompt> Which of the following is not true regarding wilsons diseaseATP7B mutation leading to impairment in copper metabolismMost specific screening test is Urinary excretion of copperGold standard test is liver biopsyKF ring is present in upto 30 cases  <response>: KF ring is present in upto 99 of cases.ATP 7B mutation results in defective biliary copper excretion into bile as copper cant be incorporated into apoceruloplasmin.Thus copper accumulates in excess amounts in liver and brain.The copper accumulation in descemets membrane of cornea is manifested as KF rings, in the eye. 