Abstract
ObjectiveThe neutrophil-to-lymphocyte ratio (NLR) has been shown to predict adverse outcomes in several pathologic conditions. The majority of indeterminate interferon (IFN)-γ release assays were due to inadequate IFN-γ response to the phytohemagglutinin. We sought to study the value of NLR to predict an indeterminate result of QuantiFERON-TB Gold In-Tube (QFT-GIT) performed in routine laboratory practice.MethodsResults from 2,773 QFT-GIT assays were analyzed. Data collection included demographic data, the level of IFN-γ to nil, mitogen, and TB antigen of QFT-GIT, total WBC, and a differential count. We calculated the absolute neutrophil count, lymphocyte count, and NLR.ResultsOf the total, 224 (8.1%) indeterminate results were observed. Twelve (1.8%) showed indeterminate results in the NLR range from 1.71 to 2.84, but 132 (19.2%) had indeterminate results in NLR≥5.18 (p<0.0001). The likelihood ratio for indeterminate results were 2.70 (95% CI, 2.36-3.08) in NLR ≥5.18 and 1.93 (95% CI, 1.64-2.27) in lymphocyte count ≤1050/μL. NLR and neutrophil count were independent predictors for indeterminate QFT-GIT result in multiple regression analysis. The IFN-γ response to PHA was negatively associated with NLR (r=-0.33, p<0.001).ConclusionWe showed that the NLR is an independent predictor of indeterminate QFT-GIT result. Low frequency of indeterminate results in group with normal NLR may imply the importance of a balance between two cellular compartments in physiological and pathological conditions.
Highlights
The likelihood ratio for indeterminate results were 2.70 in neutrophil-to-lymphocyte ratio (NLR) 5.18 and 1.93 in lymphocyte count 1050/μL
We showed that the NLR is an independent predictor of indeterminate QuantiFERON-TB Gold In-Tube (QFT-GIT) result
Low frequency of indeterminate results in group with normal NLR may imply the importance of a balance between two cellular compartments in physiological and pathological conditions
Summary
The neutrophil-to-lymphocyte ratio (NLR) is a simple ratio of the absolute neutrophil and lymphocyte counts obtained on the differential section of the total white blood cell count (WBC) of a complete blood cell (CBC) count. NLR is a marker of inflammatory response and has been shown to be associated with poor outcomes in patients with several types of disease. The NLR has shown to be a useful marker in kidney transplantation [7], schizopherenia [8], bacterial pneumonia [9], and Alzheimer's disease [10]. The interferon-gamma (IFN-γ) release assay (IGRA) was developed after it was recognized that IFN-γ plays a critical role in regulating cell-mediated immune responses to Mycobacterium tuberculosis infection. In 2007, the QuantiFERON-TB Gold In-Tube (QFT-GIT) (Cellestis, Carnegie, Australia) became the third IGRA to be approved by the Food and Drug Administration (FDA) as an aid for diagnosing M. tuberculosis infection and has improved the limitations of a previous version of IGRA [11]. Interpretation criteria for QFT-GIT approved by the FDA were positive, negative, and indeterminate. The indeterminate interpretation has indicated an uncertain likelihood of M. tuberculosis infection
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