Polymerase chain reaction (PCR) is a laboratory technique specific for diagnosing Lyme disease. PCR allows for the detection of Borrelia burgdorferi, the bacteria responsible for Lyme disease, by amplifying its DNA present in a sample. The heterophil antibody test is used to diagnose mononucleosis, not Lyme disease. Changes in serum calcium or potassium levels are not associated with Lyme disease diagnosis.