First and second sets of receptacles containing reagents for first and second amplification reactions, respectively, are placed in first and second receptacle holders, each associated with a thermal element. The receptacles are subjected to different first and second incubation processes resulting in the first and second amplification reactions in each of the first and second sets of receptacles that contain a first or a second target nucleic acid, respectively. The presence or absence of the first or second target nucleic acid, if any, is determined for each receptacle of the first and second sets of receptacles.