Methods and apparatus for use in connection with the performance of the polymerase chain reaction are provided. An exemplary sample processing module is described that includes a sample assembly and a PCR assembly, the sample processing module being configured to hold the sample therein at a pressure higher than ambient pressure. A sample is added to the sample assembly at the time of use, which is then connected to the PCR assembly. Embodiments of the cartridge include a flow restriction device that enables or aids in creating a higher pressure within the reaction vial. The sample is introduced into a PCR reaction vial, which contains all of the constituents of a PCR reaction mixture that are necessary to process the sample and provide amplified DNA of interest, if that DNA was present in the sample.