Performance and variability of QuantiFERON Gold Plus assay associated with phlebotomy type

Area of Science:

• Infectious Diseases
• Clinical Diagnostics
• Tuberculosis Screening

Background:

• The QuantiFERON Gold Plus (Plus) assay offers two blood collection methods: direct in-tube (Plus direct) and blood transfer from a lithium heparin tube (Plus transfer).
• Limited data exists comparing QuantiFERON Gold In-Tube (Gold) results with the Plus assay based on blood collection methods.

Purpose of the Study:

• To compare the performance of QuantiFERON Gold (Gold) and QuantiFERON Gold Plus (Plus) assays using direct in-tube and blood transfer methods for tuberculosis infection screening.
• To evaluate the agreement between different blood collection methods for the Plus assay and the Gold assay.

Main Methods:

• A study was conducted with 300 high-risk healthcare workers undergoing annual tuberculosis infection screening.
• Blood samples were collected concurrently for QuantiFERON Gold In-Tube (Gold), QuantiFERON Gold Plus direct in-tube (Plus direct), and QuantiFERON Gold Plus transfer (Plus transfer) assays.

Main Results:

• The proportion of positive results was 10% for Gold, 12% for Plus direct, and 17% for Plus transfer.
• Agreement between Gold and Plus direct was 91% (κ = 0.56), Gold and Plus transfer was 91% (κ = 0.59), and Plus direct and Plus transfer was 85% (κ = 0.37).

Conclusions:

• The Gold Plus assay yielded a higher proportion of positive tuberculosis infection results compared to the Gold assay in a low-prevalence setting.
• Unexpectedly low agreement was observed between the assays and collection methods, highlighting potential variability with blood transfer protocols.