Impact of the interferon-γ release assay and glomerular filtration rate on the estimation of active tuberculosis risk before bronchoscopic examinations: a retrospective pilot study

In-hospital blood collection increases the rate of indeterminate results in interferon-gamma release assays

Background:

The interferon (IFN)-γ release assay (IGRA) has recently been established as a method to evaluate the infection status of tuberculosis instead of the tuberculin skin test. However, indeterminate results can create challenges to interpretation. The IGRA has been available in Japan since 2005, including the recently launched QuantiFERON-TB Gold Plus (QFT-plus) assay.

Objectives:

The aim of this study was to investigate the clinical features and predictors of indeterminate results by the QFT-plus test in routine practice.

Methods:

This was a cross-sectional study of 1258 patients. Multivariate logistic regression models were employed to investigate the clinical factors related to indeterminate results by the QFT-plus.

Results:

Overall, 91.8% of results were found to be conclusive and 8.2% were indeterminate. The QFT-plus indeterminate results were predominantly due to a low level of IFN-γ production by mitogens. Multivariate analysis indicated that an indeterminate result was significantly associated with age, sex, corticosteroid use, autoimmune disease, and inpatient setting.

Conclusion:

Certain types of individuals are at higher risk of an indeterminate IGRA result. The QFT-plus test for hospitalized patients should be avoided as much as possible, and it is better to perform the test for those patients in outpatient settings.

Combination of anti-glycopeptidolipid-core IgA antibody and clinical features for diagnosing potential nontuberculous mycobacterium pulmonary disease in routine practice

Background:

The anti- Mycobacterium avium complex (MAC) antibody test measures levels of IgA antibody against the glycopeptidolipid (GPL) core in the bacterial cell walls and is a useful clinical indicator of nontuberculous mycobacterium pulmonary disease (NTM-PD). However, it is not currently possible to diagnose the disease using anti-MAC antibodies alone.

Objectives:

The study aim was to assess the efficacy of the combination of anti-MAC antibodies and clinical findings for diagnosing potential NTM-PD.

Methods:

This cross-sectional study included 938 patients tested using the anti-MAC antibody. NTM-PD was diagnosed by multiple positive cultures of the same species in sputum samples. Multivariate logistic regression models were used to identify the clinical factors related to NTM-PD.

Results:

Overall, 19.6% (184/938) of participants were diagnosed with NTM-PD. In multivariate analysis, positive anti-MAC antibodies, low body mass index, absence of malignancy, and cavity-forming lung lesions were significantly associated with NTM-PD at diagnosis. The positive rates of the anti-MAC antibody test were 79.4% (135/170) for MAC and 55.6% (5/9) for Mycobacterium abscessus complex, respectively.

Conclusions:

Bronchoscopic examinations should be performed especially in certain types of individuals from whom sputum samples cannot be obtained. Anti-MAC antibodies are also positive in patients other than those harboring MAC, but the rate may be low because of the different components in GPLs.