Higher T-SPOT.TB threshold may aid in diagnosing active tuberculosis?: A real-world clinical practice in a general hospital

Integrating systemic immune-inflammation index, fibrinogen, and T-SPOT.TB for precision distinction of active pulmonary tuberculosis in the era of mycobacterial disease research

Background

The clinical challenge of differentiating suspected tuberculosis with positive T-SPOT.TB results persist. This study aims to investigate the utility of the Systemic Immune-Inflammation Index (SII), Fibrinogen, and T-SPOT.TB in distinguishing between active pulmonary tuberculosis (PTB) and non-tuberculous lung diseases.

Methods

A retrospective analysis included 1,327 cases of active PTB with positive T-SPOT.TB results and 703 cases of non-tuberculous lung diseases from May 2016 to December 2020 at Meizhou People's Hospital. These were designated as the case group and the control group, respectively. The detection indicators of T-SPOT.TB: Early Secreted Antigenic Target 6 (ESAT-6), Culture Filtrate Protein 10 (CFP-10), as well as SII and Fibrinogen levels-were compared and analyzed for association and joint diagnostic value between the two groups.

Results

The case group showed higher values of ESAT-6, CFP-10, SII, and Fibrinogen compared to the control group (all p < 0.001). In the case group, SII and Fibrinogen did not correlate with ESAT-6 and CFP-10 (∣rs∣ all < 0.3) but were positively correlated with C-reactive protein (CRP; rs all > 0.3). SII and Fibrinogen values in smear-positive pulmonary tuberculosis were higher than in smear-negative cases (all p < 0.05). The optimal diagnostic thresholds for ESAT-6, CFP-10, SII, and Fibrinogen in differentiating between active PTB and non-tuberculous lung diseases were 21.50 SFCs/106 PBMC, 22.50 SFCs/106 PBMC, 2128.32, and 5.02 g/L, respectively. Regression logistic analysis showed that ESAT-6 < 21.5 (OR: 1.637, 95% CI: 1.311-2.043, p < 0.001), CFP-10 < 22.5 (OR: 3.918, 95% CI: 3.138-4.892, p = 0.025), SII < 2128.32 (OR: 0.763, 95% CI: 0.603-0.967, p < 0.001), and FIB < 5.02 (OR: 2.287, 95% CI: 1.865-2.806, p < 0.001) were independent risk factors for active PTB. The specificity for ESAT-6 + CFP-10, ESAT-6 + CFP-10 + SII, ESAT-6 + CFP-10 + FIB, and ESAT-6 + CFP-10 + SII + FIB was 82.5%, 83.2%, 95.8%, and 80.1%, respectively, while sensitivity was 52.6%, 53.0%, 55.8%, and 44.7%, and positive predictive values were 85.0%, 85.6%, 84.1%, and 89.6%, respectively.

Conclusion

SII and Fibrinogen are positively correlated with the degree of tuberculosis inflammation and the bacterial load of Mycobacterium tuberculosis. The combined detection of SII, Fibrinogen, and T-SPOT.TB is significant in distinguishing between active PTB with positive T-SPOT.TB results and non-tuberculous lung diseases.

Clinical Features and Risk Factors for Active Tuberculosis in Takayasu Arteritis: A Single-Center Case-Control Study

Backgrounds

Takayasu arteritis (TAK) is a chronic, granulomatous vasculitis correlated with tuberculosis (TB). The two diseases share similar pathological characteristics and clinical manifestations which increase the difficulty to diagnose. Active tuberculosis (ATB) has implications for treatment strategies in TAK patients. Therefore, the investigation of clinical features and potential risk factors of ATB in TAK patients is vital.

Methods

The study reviewed hospitalized patients diagnosed with TAK in our hospital from 2008, to 2021. TAK patients with ATB were enrolled as the case group. The control group was randomly selected in a 3:1 ratio. The clinical characteristics of TAK patients with and without ATB were compared. Multivariate logistic regression analysis was performed to determine risk factors for ATB in TAK patients.

Results

We reviewed 1,789 patients and ultimately identified 30 (1.7%) ATB cases. TAK patients with ATB were more prone to develop symptoms including fever (p=0.001), fatigue (p=0.003), cough (p=0.037), expectoration (p<0.001), weight loss (p=0.003), and night sweating (p<0.001). Increased level of hypersensitive C reactive protein (hsCRP, p=0.001), decreased level of albumin (p=0.031), and higher positive rate of T-SPOT.TB test (p<0.001) were observed in the case group. Multivariate logistic regression analysis revealed that hsCRP >8 mg/L (OR 9.108; 95% CI, 1.096-75.711; p=0.041) and positive T-SPOT.TB result (OR 68.669; 95% CI, 7.291-646.738; p<0.001) were risk factors for ATB in TAK patients. The proportion of patients undergoing subsequent surgery for Takayasu arteritis was lower in patients with ATB (p<0.001).

Conclusion

Our study suggested that the diagnosis of ATB should be considered when TAK patients experienced symptoms including fever, fatigue, weight loss, etc. hsCRP >8 mg/L and positive T-SPOT.TB result were identified as independent risk factors for ATB in TAK patients.

The TBAg/PHA ratio in T-SPOT.TB assay has high prospective value in the diagnosis of active tuberculosis: a multicenter study in China

Background

The positive rate of pathogenic examination about tuberculosis is low. It is still difficult to achieve early diagnosis for some TB patients. The value of Interferon-gamma release assays (IGRA) in the diagnosis of active tuberculosis remains controversial. The purpose of this multicenter prospective study was to verify and validate the role of TBAg/PHA ratio (TB-specific antigen to phytohaemagglutinin) of T-SPOT.TB assay in diagnosing ATB.

Methods

We prospectively enrolled 2390 suspected pulmonary tuberculosis patients with positive T-SPOT assay results from three tertiary hospitals.

Results

A total of 1549 ATB (active tuberculosis) patients (including 1091 confirmed and 458 probable ATB) and 724 non-tuberculosis (non-TB) patients with positive T-SPOT results were included. The results of this study showed that ESAT-6 and CFP-10 in the T-SPOT.TB assay were significantly higher in the ATB group compared with the non-TB group, while PHA was lower in the ATB group. Results of ESAT-6, CFP-10 and PHA show a certain diagnostic performance, but moderate sensitivity and specificity. The TBAg/PHA ratio, a further calculation of ESAT-6, CFP-10 and PHA in T-SPOT.TB assay showed improved performance in the diagnosis of active Tuberculosis. If using the threshold value of 0.2004, the specificity and sensitivity of TBAg/PHA ratio in distinguishing ATB from non-TB were 92.3% and 74.4%, PPV was 95.4, PLR was 9.6.

Conclusion

By recalculating the results of T-SPOT.TB Assay, the TBAg/PHA ratio shows high prospect value in the diagnosis of active tuberculosis in high prediction areas.