New method extracts DNA from QuantiFERON-TB Gold tubes for research

Latent tuberculosis infection (LTBI) is a persistent global challenge, and tests like the QuantiFERON-TB Gold (QFT) assay are widely used to diagnose it. But blood collected in QFT tubes is rarely used for genetic or molecular studies because the tubes contain heparin and a dense gel barrier that make it hard to get DNA out. That has forced researchers and clinicians to take extra blood samples when they want to do DNA-based tests, adding cost and complexity. In response, Sidra Younis and colleagues set out to develop a straightforward method to extract high-quality DNA directly from blood already collected in QFT tubes. The goal was practical: allow the same sample used for LTBI immunodiagnosis to be used for downstream molecular work such as PCR and sequencing, so labs do not need extra sampling and can more easily combine routine testing with genomic research.

To tackle the extraction problem the team used a hybrid approach that started with manual lysis and then applied three commercial kits: Thermo Scientific GeneJET, QIAamp DNA Blood Kit, and FavorPrep™ Blood Genomic DNA Extraction Kit. They compared DNA from QFT tubes with DNA from standard EDTA tubes. DNA concentration and purity were measured on a Multiskan SkyHigh Microplate Spectrophotometer and DNA integrity was checked by agarose gel electrophoresis. To show the DNA worked in molecular tests, they ran ARMS-PCR and performed whole exome sequencing (WES). They found no differences between EDTA and QFT tubes in amount, purity, or suitability for PCR and sequencing. Extracted DNA had A260/280 ratios of 1.7–1.9 and concentrations of 4.9–118.5 µg/mL. Agarose gels showed intact genomic DNA and clear PCR bands. WES yielded 6.47–8.71 GB per sample, 42.8–57.7 M reads, GC content 49.29%–52.54%, with Q20 over 98.6% and Q30 above 95%.

The study presents an optimized, reproducible protocol that turns QFT tubes into a source of DNA suitable for both PCR-based assays and next-generation sequencing. By showing equivalent performance between QFT and EDTA tubes, the work removes a practical barrier that has kept QFT-collected blood out of molecular workflows. This has clear advantages for diagnostic laboratories: it can save time and resources by removing the need for extra blood draws, make better use of routine clinical specimens, and allow combined immunodiagnostic and genomic analyses from the same sample. The authors highlight the approach as cost-effective and especially useful in resource-limited settings, and they suggest it could support future biomarker discovery and precision diagnostics research by enabling wider integration of genomic methods into TB testing pipelines.