Molecular Tests

Specimens were tested using CapitalBio assay and/or Xpert. For CapitalBio assay, the specimens were added to the buffer; a homogeneous suspension was obtained by grinding, and 1 mL was obtained. The 1-mL sample was added to 2 mL of the specimen preparation solution to obtain liquefied specimens. Then, 1 mL liquefied specimens were centrifuged to obtain sediment. Then, the sediment was used for nucleic acid extraction. Then, 2 µL extracted DNA was used according to the manufacturer’s instructions. A fluorescence quantification RT-PCR instrument (SLAN-96S Real-Time PCR System ZEESAN Xiamen CN) was used to amplify and detect IS6110 multicopy elements for MTB. The test results were available in ~3 hours.¹⁹ For Xpert, 1 mL of the specimen and 2 mL of the specimen reagent were mixed. The mixture was agitated for 20s and incubated at room temperature for 15 min. Next, 2 mL of the treated specimen solution was added to the Xpert reaction cartridge and placed in the assay module to initiate automatic assay. The system automatically read the MTB assay results within 2 hours.²⁰ A positive test for either CapitalBio assay or Xpert was considered a positive molecular test.