Abstract: The present invention relates to a new method for determining the allele frequency and/or mutation rate in nucleic acids, in particular in tumor nucleic acids, in the context of a polymerase chain reaction (PCR), and to diagnostics for this purpose, wherein at least one reference nucleic acid (RN) and one mutation sequence with respect to the reference nucleic acid are used. This reference nucleic acid and mutation sequence allows polymerase chain reaction (PCR) methods to be validated, in particular on the basis of device parameters and sample preparation. Furthermore, the invention relates to an associated diagnosis and prognosis method, in particular for tumor diagnosis as part of a liquid biopsy.