qualified diagnostics research taxpayer that receives credit that has been transferred shall use such credit for the taxable year in which the transfer occurred. Any unused amounts of such credit may be carried back or forward to other taxable years in accordance with section 39. (3) Definition of qualified diagnostics research taxpayer For purposes of this section, the term qualified diagnostics research taxpayer means any domestic corporation that derives— (A) any gross income from research or development on diagnostic tests used to identify or detect the presence, concentration or characteristics of a serious or life-threatening infectious disease or pathogen