Q. A 32-year-old female is admitted with complaints of recurrent fever, chills, and night sweats over the past two weeks. She reports feeling fatigued and has lost weight without trying. The patient has a history of intravenous drug abuse and was recently diagnosed with HIV infection. She is currently taking antiretroviral therapy and has been compliant with her medication regimen. She reports no other significant medical history. The patient is febrile, with a temperature of 101.5 degrees Farenheit. She appears pale and fatigued. Her lungs are clear, and her heart sounds are regular with no murmurs or gallops. Her abdomen is soft and non-tender, with no hepatosplenomegaly. There are no visible skin lesions or rashes. Given the patient's history of HIV infection and recurrent fever, you order an ELISA test to screen for other infections that may be contributing to her symptoms. The results of the ELISA test show positive antibodies to Mycobacterium avium complex. The patient is started on a course of antibiotics to treat the MAC infection and is referred to an infectious disease specialist for further management of her HIV infection. The ELISA test is an important diagnostic tool. Which of the following is NOT considered a standard step in completing an enzyme linked immunosorbent assay?