PURPOSE: To rapidly extract, amplify and detect the subject nucleic acid for the diagnosis of infectious diseases by heating an aqueous specimen of peripheral blood mononuclear cells to the boiling point of water so as to dissolved the cells and extracellularly discharge the nucleic acid, recovering the nucleic acid from a low level and amplifying the same by polymerase chain reaction.

CONSTITUTION: An aqueous specimen of peripheral blood monomolecular cells expected to contain a nucleic acid derived from an infectious body or human genom is heated at or near the boiling point of water for 2 to 15 minutes so as to dissolve the cell in the specimen for discharging the nucleic acid derived from the cell. The objective nucleic acid can be determined by recovering the nucleic acid from the heated specimen, amplifying the nucleic acid by a polymerase chain reaction, detecting the amplified nucleic acid by forming a hybrid product with a complementary primer or the like.