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

Saroochi Agarwal,Duc T Nguyen,Edward A Graviss,Justin D Lew,Marc Tebruegge

doi:10.1371/journal.pone.0207892

Abstract

BackgroundQuantiFERON Gold Plus (Plus) assay has two approved methods for blood collection: direct in-tube (Plus direct) or the transfer of blood from a lithium heparin tube (Plus transfer). Currently, there is little data comparing the results of Plus and the QuantiFERON Gold In-Tube (Gold) based on blood collection.MethodsIn 2017, high risk healthcare workers undergoing annual tuberculosis infection screening at Houston Methodist Hospital, a private hospital in the Texas Medical Center (Houston, TX, U.S.A.) were consented and enrolled in a study comparing the Gold-in-tube (Gold), Plus direct in-tube, and Plus transfer assays. Blood was drawn concurrently for all 3 assays.ResultsPhlebotomy occurred on 300 consecutive, consented and enrolled participants in the study. The proportion of positive test results for the Gold, Plus direct and Plus transfer assays were 10% (29/300), 12% (35/299) and 17% (51/299), respectively. The agreement in the results of Gold versus Plus direct, Gold versus Plus transfer, and Plus direct versus Plus transfer was 91%, kappa (κ) = 0.56; 91%, κ = 0.59; and 85%, κ = 0.37, respectively.ConclusionsAmong high risk healthcare workers in a low prevalence tuberculosis setting, the Gold Plus assay had a higher proportion of positive results than the Gold in-tube assay. The agreement between the Gold, Plus direct and Plus transfer assays was unexpectedly low for simultaneously obtained samples. Blood transfer using lithium heparin offers individual clinics and public health programs greater ability to customize protocols, but variability of results still exists.

Highlights

There are several diagnostic and screening assays for tuberculosis (TB) infection (TBI) including the tuberculin skin test (TST) and interferon gamma release assays (IGRAs), which include the QuantiFERON-TB Gold in-tube (QFT-G) (QIAGEN, Germantown, MD, USA) and T-SPOT.TB (Oxford Immunotec, Inc., Marlborough, MA, USA) assays
Among high risk healthcare workers in a low prevalence tuberculosis setting, the Gold Plus assay had a higher proportion of positive results than the Gold in-tube assay
QuantiFERON Plus comparison study tubes and kits were provided in-kind by QIAGEN Inc., the company had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Summary

Introduction

There are several diagnostic and screening assays for tuberculosis (TB) infection (TBI) including the tuberculin skin test (TST) and interferon gamma release assays (IGRAs), which include the QuantiFERON-TB Gold in-tube (QFT-G) (QIAGEN, Germantown, MD, USA) and T-SPOT.TB (Oxford Immunotec, Inc., Marlborough, MA, USA) assays. A new IGRA, QuantiFERON-TB Gold Plus (QFT-P) (QIAGEN, Germantown, MD, USA), was approved by the U. The QFT-P is approved for a direct in-tube phlebotomy draw or an indirect phlebotomy draw into a lithium heparin (LiHp) tube, where the blood is subsequently transferred into the four QFT-P tubes. This standardized transfer procedure is expected to reduce indeterminate results caused by pre-analytical errors such as tubes not being shaken as the transfer will be conducted in the laboratory by trained technicians [1]. There is little data comparing the results of Plus and the QuantiFERON Gold In-Tube (Gold) based on blood collection

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