A test method for determining total isotropic sensitivity (TIS) of a mobile wireless communications device including a radio frequency (RF) receiver and an antenna coupled thereto may include measuring a sensitivity of the RF receiver, and measuring a three-dimensional (3D) gain pattern of the antenna independent of measuring the sensitivity of the RF receiver. The method may further include determining the TIS of the mobile wireless communications device based upon the sensitivity of the RF receiver and the 3D gain pattern of the antenna.