Background: A review of the scientific literature concluded that indirect smear can improve detection of TB in sputum compared to direct smear. However few laboratories have access to centrifugation in order to perform indirect smear. This study investigated whether an alternative method of magnetic bead concentration could enhance diagnosis of TB in China in laboratories which only perform direct smear microscopy.
Methods: A total of 129 sputum samples were investigated by direct smear microscopy, microscopy after TB-Bead extraction and by solid and liquid culture.
Results: Direct smear had a sensitivity of 40% by Ziehl-Neelsen (ZN) and 45% by auramine compared to combined culture results. After TB-Bead extraction, this increased to 65% for ZN and 70% for auramine.
Conclusion: Magnetic bead concentration of mycobacteria from sputum led to a significant improvement (p<0.05) in the sensitivity of microscopy compared with direct smear.
Keywords: Magnetic beads; Mycobacterium tuberculosis; Smear microscopy; TB-Beads.