[Application and process optimization of automated magnetic bead sorting technology in T-SPOT.TB assay for...

To evaluate the clinical application value of magnetic bead sorting technology (MBS) using the T-cell select kit combined with an automatic cell sorter for isolating peripheral blood mononuclear cells (PBMCs) to realize automated specimen pre-processing and process optimization in T-SPOT.TB assay. A cross-sectional study was conducted involving 300 patients recruited from the first affiliated hospital of Air Force Medical University from March 2023 to July 2024. Among them, there were 167 males and 133 females. The age range of the patients was 18 to 65 years, with a median age of 49.0 (33.3, 59.0) years and a mean age of (46.4±13.9) years. 4 ml of anticoagulated whole blood samples in duplicate were collected from each patient. One fresh sample (0-4 h) was processed immediately using density gradient centrifugation (DGC) for PBMC isolation, while the other was processed using MBS method at either 0-4 h or 34-54 h post-collection. The cycles for cell enrichment step of the automatic cell sorter were adjusted from the conventional 4 cycles to 2 cycles. Statistical analysis was performed using Cohen's Kappa test to evaluate the concordance of T-SPOT.TB results across all processing groups. The results showed that for fresh samples (0-4 h), the T-SPOT.TB results for samples processed with 4-cycle and 2-cycle MBS enrichment steps demonstrated positive concordance rates of 91.7% and 93.1%, negative concordance rates of 100% for both, overall concordance rates of 98.0% and 97.9%, and Kappa values of 0.94 and 0.95, respectively, compared with the reference results for paired samples processed using DGC. Correspondingly, the results for samples processed with the 4-cycle and 2-cycle MBS methods at 34-54 h post-collection yielded positive concordance rates of 90.0% and 81.3%, negative concordance rates of 95.1% and 100%, overall concordance rates of 93.0% and 82.9%, and Kappa values of 0.86 and 0.43, respectively, compared with the reference results for fresh samples processed using DGC. In conclusion,for 0-4 h samples, the T-SPOT.TB results from both 4-cycle and 2-cycle MBS enrichment protocols were highly consistent with the reference results from conventional DGC methods. However, for 34-54 h stored samples, results from the 4-cycle MBS method rather than the 2-cycle protocol exhibited significantly superior concordance with the reference results. The MBS method using T-Cell Select kit achieves automated sample pre-processing for T-SPOT.TB assay, reduces hands-on time, and provides a viable alternative with reliable results for long-stored specimens.