Increased rates of indeterminate results in QuantiFERON-TB gold in-tube during the COVID-19 epidemic in Hunan province, China.

Increased rates of indeterminate QuantiFERON-TB Gold In-Tube (QFT-GIT) results have been reported since the COVID-19 epidemic in Hunan Province, China. The indeterminate result (ITR) rate of QFT increased from an average of 5.2% to 12.4%, paralleling the first COVID-19 pandemic wave in the region. QFT-GIT results of 243 hospitalized patients with COVID-19 from January 2022 to April 2023 at Xiangya Hospital of Central South University were analyzed. Of the 243 patients, 71 (29.2%) had ITRs due to reduced interferon-gamma production in the positive control. Multiple factors are associated with ITRs, such as disease severity, respiratory failure incidence, immunosuppressant use, and prognosis. Additionally, interferon-gamma (Mitogen-Nil) levels differed significantly depending upon disease severity, prognosis, immunosuppressant use, sepsis symptoms, respiratory failure, or hyperlipidemia. An abnormal increase in the ITR rate in the QFT was observed after the COVID-19 pandemic, and an optimal machine learning predictive model for indeterminate QFT results was established.

Indeterminate results of QuantiFERON-TB Gold in-tube due to high nil concentration and methodological exploration and improvement.

BACKGROUND: The features of indeterminate results (ITRs) due to high interferon gamma (IFN-γ > 8.0 IU/mL) concentrations in Nil tubes of QuantiFERON-TB Gold in-Tube (QFT-GIT) have not been well studied. Therefore, this study aimed at investigating the features of ITRs and optimization alternatives for this method. METHODS: We used the plasma exchange method to reduce the ITR rate due to high Nil concentrations (Nil > 8.0 IU/mL) between March 2020 and September 2021 at Xiangya Hospital of Central South University in China. One hundred and eleven out of 28,193 patient samples were considered ITRs due to Nil > 8.0 IU/mL. Of these 111, blood was re-sampled from 82 patients (pretreated group) who received the plasma exchange. Moreover, 40 out of 82 (blood volume ≥ 5 mL) received pretreated QFT-GIT and standard QFT-GIT (untreated group) simultaneously, while the remaining 42 received pretreated QFT-GIT only. The statistical difference between groups was evaluated. Cohen's kappa coefficient was used to assess the level of agreement between the pretreated and untreated group. RESULTS: Of the 28,193 subjects, 1,083 (3.8%) had ITRs, and 111 (0.4%) had ITRs due to Nil > 8.0 IU/mL. The population studied had a mean age of 52.9 years, and 70.3% were men, which is a larger proportion than that in patients with ITR and the overall population. Significantly decreased IFN-γ levels in Nil tubes were detected using the pretreated QFT-GIT compared with standard QFT-GIT (p < 0.01). The determinate results rate in the pretreated group was significantly higher than that of the untreated group (80% (32/40) vs 57.5%, (23/40), p = 0.03). Further comparison revealed that the pretreated group was consistent with the untreated group in 17/20 (85%) positive tests, 3/3 (100%) negative tests, and 6/17 (35.3%) ITRs. The overall agreement rate was 26/40 (65%) among all 40 subjects, and the κ value was 0.39 (minimal agreement). The majority of results obtained after pretreatment were positive (71.2%, 59/82) and the agreement rate between clinical diagnosis and pretreated QFT-GIT was at least 61.0% (39/59). CONCLUSION: Plasma exchange pretreated QFT-GIT yields more reliable results than untreated QFT-GIT when processing high Nil concentrations.

Correlation of PMN elastase and PMN elastase-to-neutrophil ratio with disease activity in patients with myositis.

BACKGROUND: Polymorphonuclear (PMN) elastase plays an important role in a variety of inflammatory disorders. Our aim was to analyse PMN elastase in idiopathic inflammatory myopathies (IIMs) and its association with disease activity. METHODS: PMN elastase levels were measured using enzyme-linked immunosorbent assay in serum samples obtained from 74 patients with myositis (58 with dermatomyositis [DM] and 16 with polymyositis [PM]) and 22 healthy controls. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the discriminant capacity of PMN elastase level and PMN elastase-to-neutrophil ratio (ENR) in patients with active and remission myositis. The association of serum PMN elastase level and ENR with disease variables was evaluated in patients with IIMs. The disease specificity of PMN elastase level and ENR was further examined in 60 patients with other systemic autoimmune diseases. RESULTS: PMN elastase level and ENR were significantly higher in patients with active IIMs, DM, and PM than in patients with remission. ROC curve analysis revealed that PMN elastase level and ENR both outperformed creatine kinase (CK), the currently used laboratory marker, and strongly discriminated patients with active disease and those with remission of IIMs, DM, and PM (area under the ROC curve [AUC] 0.9, 0.9, and 0.88 for PMN elastase; AUC 0.96, 0.96, and 1.0 for ENR; AUC 0.72, 0.70, and 0.80 for CK, respectively). PMN elastase level and ENR were positively correlated with myositis disease activity assessment, CK, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, C-reactive protein, and erythrocyte sedimentation rate. PMN elastase level and ENR were higher in the anti-PM-Scl positive myositis group than those in the anti-PM-Scl negative myositis group. Nevertheless, PMN elastase was not a specific disease marker for IIMs when compared with other autoimmune diseases. CONCLUSIONS: PMN elastase, particularly ENR, were significantly correlated with disease activity and could serve as useful biochemical markers for evaluating the disease activity of patients with IIMs. Thus, they are potentially helpful in monitoring disease progression and guiding treatment.