In case of the immuno- and DNA sensors, the mass shift related to binding the analyte molecule can be directly measured by the QCM sensor. The sensitivity of such detection depends on the mass of the analyte molecule and the density of the binding sites on the surface of the QCM transducers. As mentioned, the latter contribution is limited by the necessity of monolayer filling of the transducer surface. For this reason, the analytical characteristics of the direct formats of the piezoelectric detection are rather moderate and cannot compete with those of electrochemical and optosensors. Thus, the detection of hybridization can be performed with the LODs of about 10−8 to 10−9 M against the femtomolar ranges reached by electrochemical and fluorescent labels.