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. 2021 Sep 24;10(19):4357.
doi: 10.3390/jcm10194357.

Frequency and Factors of Indeterminate QuantiFERON-TB Gold In-Tube and QuantiFERON-TB Gold PLUS Test Results in Rheumatic Diseases

Sung Soo Ahn  1 , Hyung Woo Kim  2 , Younhee Park  3
Affiliations

Frequency and Factors of Indeterminate QuantiFERON-TB Gold In-Tube and QuantiFERON-TB Gold PLUS Test Results in Rheumatic Diseases

Sung Soo Ahn et al. J Clin Med. .

Abstract

We compared the results and differences of indeterminate rates between the QuantiFERON-TB Gold In-Tube (QFT-GIT) and QuantiFERON-TB Gold PLUS (QFT-PLUS) tests in patients with rheumatic diseases and analyzed the associated factors. Data of patients with rheumatic diseases who had undergone the QFT-GIT or QFT-PLUS test were used, and information regarding patient demographics, primary diagnosis, laboratory results, and medications was collected. Furthermore, indeterminate result rates of the patient cohort and healthy controls were also compared. A total of 177 (43.4%) and 231 (56.6%) patients had undergone QFT-GIT and QFT-PLUS tests, respectively. Among them, four (2.3%) and seven (3.0%) patients had indeterminate results, which did not differ between the QFT-GIT and QFT-PLUS groups. Indeterminate results were significantly higher among patients with rheumatic diseases than in healthy controls (2.7% vs. 0.2%, p < 0.001). Multivariate logistic regression revealed that the lymphocyte count (hazard ratio (HR) 0.998, 95% confidence interval (CI) 0.997, 1.000; p = 0.012) and albumin level (HR 0.366, 95% CI 0.150, 0.890; p = 0.027) were predictive of indeterminate results. A lymphocyte count of ≤810/mm3 and an albumin level of ≤3.7 mg/dL were capable of discriminating between indeterminate and determinate results. The QFT-GIT and QFT-PLUS tests have comparable diagnostic performances in patients with rheumatic diseases. Decreased lymphocyte and albumin levels contribute to indeterminate results.

Keywords: QuantiFERON-TB Gold In-Tube; QuantiFERON-TB Gold PLUS; factors; indeterminate; rheumatic diseases.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Patient selection and exclusion. QFT-GIT: QuantiFERON-TB Gold In-Tube; QFT-PLUS: QuantiFERON-TB Gold PLUS.
Figure 2
Figure 2
Cut-off values of absolute lymphocyte count and albumin levels associated with indeterminate results. In the receiver operating characteristic curve analysis, (A) a lymphocyte count of ≤810 mm3 or (B) an albumin level of ≤3.7 mg/dL was capable of discriminating between indeterminate and determinate results of interferon-gamma release assays. AUC: area under the curve; CI: confidence interval.
Figure 3
Figure 3
Relative risk of indeterminate results according to lymphocyte count and albumin level. Patients with (A) a lymphocyte count of ≤810 mm3 and (B) an albumin level of ≤3.7 mg/dL had a significantly higher risk of indeterminate results being reported than those who did not meet these criteria. In addition, the RR increased in those with both (C) a lymphocyte count of ≤810 mm3 and an albumin level of ≤3.7 mg/dL. RR: relative risk.
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