The Use of TB-Specific Antigen/Phytohemagglutinin Ratio for Diagnosis and Treatment Monitoring of Extrapulmonary Tuberculosis

Diagnostic Values of Peripheral Blood T-Cell Spot Test for Tuberculosis (T-SPOT.TB) for Spinal Tuberculosis

Background: The T-cell spot test for tuberculosis (T-SPOT.TB) with false positives and false negatives exists in the diagnosis of spinal infection. The objective of this study was to increase the diagnostic value precision and specificity of T-SPOT.TB in the identification of spinal tuberculosis (TB). Patients and Methods: Fifty-two patients suspected of having spinal TB from April 2020 to December 2021 were included, and all patients received T-SPOT.TB tests and surgical treatment. The composite reference standard was used to diagnose spinal TB. The T-SPOT.TB values were compared according to whether spinal TB was diagnosed, and the optimal cutoff values of diagnosis was determined by receiver operating characteristic (ROC) curve analysis. Results: All patients were followed up for at least one year. The sensitivity, specificity, positive predictive value, and negative predictive value of the T-SPOT.TB test in assisting the diagnosis of spinal TB were 91.67%, 71.43%, 73.33%, and 90.9%, respectively. We determined that the values of early secreted antigen target 6 (ESAT-6) antigen and culture filter protein 10 (CFP-10) antigen were determined to be diagnostic for spinal tuberculosis, with areas under the curve equal to 0.776 and 0.852, respectively; the cutoff values for the diagnosis of ESAT-6 antigen and CFP-10 antigen were calculated as 40.5 spot forming cells (SFCs) per 10⁶ peripheral blood mononuclear cells (PBMCs) and 26.5 SFCs/10⁶ PBMCs, respectively. Follow-up for all patients was 12 months, and in this period, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), visual analog scale (VAS) score, and Oswestry Dysfunction Index (ODI%) were different between groups (p < 0.05). Conclusions: The T-SPOT.TB test is considered a milestone discovery in the diagnosis of TB; there are still many false-positive samples, but the diagnostic specificity was improved in the study, allowing spinal infections to be treated accurately and in a timely manner.

Identification of host biomarkers from dried blood spots for monitoring treatment response in extrapulmonary tuberculosis

There is a lack of objective tools for monitoring treatment response in extrapulmonary tuberculosis (EPTB). This study aimed to explore the utility of inflammatory biomarkers from the dry blood spots (DBS) as a tool for monitoring treatment response in EPTB. In a prospective cohort study, 40 inflammatory biomarkers were investigated in DBS samples from 105 EPTB cases using a Luminex platform. The samples were taken before, and, at the end of the 2nd and 6th months of treatment. A total of 11 inflammatory host biomarkers changed significantly with treatment in all EPTB patients. CXCL9/MIG, CCL20, CCL23, CXCL10/IP-10, CXCL1, CXCL2, and CXCL8 significantly declined in our cohort of EPTB (48 TB pleuritis and 57 TB lymphadenitis) patients at both time points. A biosignature consisting of MIG, CCL23, and CXCL2, corresponded with the treatment response in 81% of patients in the 2nd month and 79% of patients at the end of treatment. MIG, CCL23, IP-10, and CXCL2 changed significantly with treatment in all patients including those showing partial clinical response at the 2nd month of treatment. The changes in the levels of inflammatory biomarkers in the DBS correspond with the treatment success and can be developed as a routine test in low-resource settings.

Preparation of a novel monoclonal antibody against active components of PHA-L from Phaseolus vulgaris and its functional characteristics

Background

Leukocyte phytohemagglutinin (PHA-L), derived from the L4 tetramer of PHA, has been frequently employed as a mitogen to induce T lymphocyte proliferation in vitro. The biological application of PHA-L in cancer diagnosis and treatment has gained traction in recent years. However, it has been noted that PHA-L obtained using traditional procedures has a massive amount of impurities or toxic components, which interfere with the activity of PHA-L. Preparation of a monoclonal antibody against active PHA-L is a significant tool for studying PHA-L's function and therapeutic potential.

Results

We successfully prepared monoclonal antibodies against the active components of PHA-L based on the whole PHA-L protein as an antigen, and found that monoclonal antibody 3C1C6G11 can be employed in western blot, immunofluorescence, and immunohistochemistry detection. Importantly, preliminary result shows that the mAb 3C1C6G11 may prevent PHA-L-induced cell aggregation and AICD (activation-induced cell death).

Conclusions

The monoclonal antibody mAb 3C1C6G11 prepared in this study can be used as an effective tool for detecting PHA-L active components, investigating PHA-L's function and antineoplastic application.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12896-022-00761-7.

Review and Updates on the Diagnosis of Tuberculosis

Diagnosis of tuberculosis, and especially the diagnosis of extrapulmonary tuberculosis, still faces challenges in clinical practice. There are several reasons for this. Methods based on the detection of Mycobacterium tuberculosis (Mtb) are insufficiently sensitive, methods based on the detection of Mtb-specific immune responses cannot always differentiate active disease from latent infection, and some of the serological markers of infection with Mtb are insufficiently specific to differentiate tuberculosis from other inflammatory diseases. New tools based on technologies such as flow cytometry, mass spectrometry, high-throughput sequencing, and artificial intelligence have the potential to solve this dilemma. The aim of this review was to provide an updated overview of current efforts to optimize classical diagnostic methods, as well as new molecular and other methodologies, for accurate diagnosis of patients with Mtb infection.

Using TBAg/PHA Ratio for Monitoring TB Treatment: A Prospective Multicenter Study

The way to monitor tuberculosis (TB) treatment is extremely lacking in clinical practice. The aim of the study is to assess the role of the TBAg/PHA ratio in the treatment monitoring of TB. TB patients were followed up for 6 months and serial T-SPOT.TB (T-SPOT) assays were performed. In patients with successful treatment outcomes, the ESAT-6 sfc, CFP-10 sfc, and TBAg/PHA ratio all showed a decreased trend after the initiation of treatment. Conversely, PHA sfc showed an increased trend after 2 months of treatment. However, these indicators had moderate performance in distinguishing between before and after 6 months of treatment, and the AUC ranged from 0.702 to 0.839. Notably, the TBAg/PHA ratio in patients without risk factors was of important value in differentiation between before and after treatment. The optimal AUC of TBAg/PHA ratio reached up to 0.890. Patients with unsuccessful treatment outcomes showed persistently high levels of TBAg/PHA ratio. The TBAg/PHA ratio in patients after 6 months of treatment showed a certain potential in distinguishing between patients with successful and unsuccessful treatment outcomes. A further calculation of the TBAg/PHA ratio in T-SPOT assay has potential value in the treatment monitoring of TB, but further confirmation is needed.

Tuberculosis-Specific Antigen/Phytohemagglutinin Ratio Combined With GeneXpert MTB/RIF for Early Diagnosis of Spinal Tuberculosis: A Prospective Cohort Study

Spinal tuberculosis (TB), the most common form of musculoskeletal tuberculosis, is an infection-related disease globally, with paraplegia occurring in severe cases. Therefore, identification of spinal TB at an early stage is important for early intervention and eventual therapy. In this study, we conducted a prospective cohort study in routine clinical practice to investigate the diagnosis of different TB tests. A total of 519 patients were recruited based on the radiology of spinal TB. The diagnostic model was computed by regression analysis and was determined by receiver operating characteristic (ROC) curve analysis. Specificity, sensitivity, predictive value, likelihood ratio, and accuracy were also computed and compared. GeneXpert MTB/RIF showed a higher positive rate compared to that in the acid-fast bacilli smear and Mycobacterium culture. The results also showed that the Mycobacterium tuberculosis-specific antigen/phytohemagglutinin ratio in the T-SPOT assay had a good performance in the preoperative diagnosis and prediction of spinal TB. The diagnostic model based on the ratio of tuberculosis-specific antigen/phytohemagglutinin combined with GeneXpert MTB/RIF showed better efficiency for spinal TB diagnosis. In summary, the tuberculosis-specific antigen/phytohemagglutinin ratio combined with GeneXpert MTB/RIF could provide an early diagnosis of spinal TB.

Diagnostic Model for Discrimination Between Tuberculous Meningitis and Bacterial Meningitis

Background

The differential diagnosis between tuberculous meningitis (TBM) and bacterial meningitis (BM) remains challenging in clinical practice. This study aimed to establish a diagnostic model that could accurately distinguish TBM from BM.

Methods

Patients with TBM or BM were recruited between January 2017 and January 2021 at Tongji Hospital (Qiaokou cohort) and Sino-French New City Hospital (Caidian cohort). The detection for indicators involved in cerebrospinal fluid (CSF) and T-SPOT assay were performed simultaneously. Multivariate logistic regression was used to create a diagnostic model.

Results

A total of 174 patients (76 TBM and 98 BM) and another 105 cases (39 TBM and 66 BM) were enrolled from Qiaokou cohort and Caidian cohort, respectively. Significantly higher level of CSF lymphocyte proportion while significantly lower levels of CSF chlorine, nucleated cell count, and neutrophil proportion were observed in TBM group when comparing with those in BM group. However, receiver operating characteristic (ROC) curve analysis showed that the areas under the ROC curve (AUCs) produced by these indicators were all under 0.8. Meanwhile, tuberculosis-specific antigen/phytohemagglutinin (TBAg/PHA) ratio yielded an AUC of 0.889 (95% CI, 0.840–0.938) in distinguishing TBM from BM, with a sensitivity of 68.42% (95% CI, 57.30%–77.77%) and a specificity of 92.86% (95% CI, 85.98%–96.50%) when a cutoff value of 0.163 was used. Consequently, we successfully established a diagnostic model based on the combination of TBAg/PHA ratio, CSF chlorine, CSF nucleated cell count, and CSF lymphocyte proportion for discrimination between TBM and BM. The established model showed good performance in differentiating TBM from BM (AUC: 0.949; 95% CI, 0.921–0.978), with 81.58% (95% CI, 71.42%–88.70%) sensitivity and 91.84% (95% CI, 84.71%–95.81%) specificity. The performance of the diagnostic model obtained in Qiaokou cohort was further validated in Caidian cohort. The diagnostic model in Caidian cohort produced an AUC of 0.923 (95% CI, 0.867–0.980) with 79.49% (95% CI, 64.47%–89.22%) sensitivity and 90.91% (95% CI, 81.55%–95.77%) specificity.

Conclusions

The diagnostic model established based on the combination of four indicators had excellent utility in the discrimination between TBM and BM.

Extrapulmonary tuberculosis

Introduction: Tuberculosis (TB) is a major cause of morbidity and mortality globally. Extrapulmonary TB (EPTB) constitutes about 15%-20% of all TB patients, but accounts for 50% among HIV-coinfected. Confirmation of microbial diagnosis of EPTB is usually challenging.Areas covered: Availability of newer imaging modalities like ¹⁸FDG-PET-CT and PET-MRI has facilitated precise anatomical localization of the lesions and mapping the extent of EPTB. The use of image- and endoscopy-guided invasive diagnostic methods has made procurement of tissue/body fluids for diagnostic testing possible. With the advent of universal drug-susceptibility testing, a rapid diagnosis of drug-resistance is now possible in EPTB. Drug-susceptible EPTB usually responds well to first-line anti-TB treatment; TB meningitis, bone and joint TB and lymph node TB requires longer durations of treatment.Expert opinion: Adjunctive use of corticosteroids in the initial period is recommended in the central nervous system and pericardial TB. Surgical intervention is helpful to obtain tissue samples for diagnosis. Adjunctive surgical treatment along with medical treatment is useful in treating complications like hydrocephalus, Pott's spine. Follow-up of EPTB patients is crucial as treatment period is usually prolonged, requires recognition of development of immune reconstitution and inflammatory syndrome (IRIS), monitoring of adverse events, serious adverse events like anti-TB drug-induced hepatotoxicity, organ-related complications, and treatment adherence.

Use of Rv0222-Rv2657c-Rv1509 Fusion Protein to Improve the Accuracy of an Antibody ELISA for Extra-Pulmonary Tuberculosis in Humans

(1) Background: Tuberculosis (TB) in humans is a serious chronic epidemic disease caused by Mycobacterium tuberculosis (M. tb). The diagnosis of TB, especially extra-pulmonary TB (EPTB), is difficult. Isolation of M. tb from culture has a low sensitivity in patients with TB and an even lower sensitivity in cases of EPTB. Although Xpert MTB/RIF assays and serological tests are more sensitive than the above tests, they still lack sensitivity for EPTB diagnosis. (2) Methods: To improve the accuracy of TB diagnosis, a Rv0222-Rv2657c-Rv1509 fusion protein based iELISA was constructed, the diagnosis of TB, pulmonary TB (PTB) and EPTB was then evaluated. Sera of 40 TB patients including 14 with PTB, 14 with EPTB and 12 with no information about the form of TB, and five pneumonia patients were investigated. (3) Results: The sensitivity of the ELISA in TB, PTB and EPTB patients was 80% (95% CI: 64.4, 90.9%), 85.7% (95% CI: 57.2, 98.2%) and 92.8% (95% CI: 66.1, 99.8%), respectively, with a specificity of 70% (95% CI: 53.5, 83.4%). Both the sensitivity and specificity with this fusion protein were higher than for CFP10/ESAT6 (used as reference antigen) fusion protein (71.4%; 95% CI: 41.9, 91.6%, and 67.5%; 95% CI: 50.9, 81.4%), respectively, in cases of EPTB. All pneumonia patients’ sera tested negative in both ELISAs. (4) Conclusion: use of these new fusion proteins as antigens in serological assays has the potential to improve the diagnosis of all forms of TB in humans, especially EPTB.

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.

Lymphocyte Non-Specific Function Detection Facilitating the Stratification of Mycobacterium tuberculosis Infection

Background

Inadequate tuberculosis (TB) diagnostics, especially for discrimination between active TB (ATB) and latent TB infection (LTBI), are major hurdle in the reduction of the disease burden. The present study aims to investigate the role of lymphocyte non-specific function detection for TB diagnosis in clinical practice.

Methods

A total of 208 participants including 49 ATB patients, 64 LTBI individuals, and 95 healthy controls were recruited at Tongji hospital from January 2019 to October 2020. All subjects were tested with lymphocyte non-specific function detection and T-SPOT assay.

Results

Significantly positive correlation existed between lymphocyte non-specific function and phytohemagglutinin (PHA) spot number. CD4⁺ T cell non-specific function showed the potential for differentiating patients with negative T-SPOT results from those with positive T-SPOT results with an area under the curve (AUC) of 0.732 (95% CI, 0.572-0.893). The non-specific function of CD4⁺ T cells, CD8⁺ T cells, and NK cells was found significantly lower in ATB patients than in LTBI individuals. The AUCs presented by CD4⁺ T cell non-specific function, CD8⁺ T cell non-specific function, and NK cell non-specific function for discriminating ATB patients from LTBI individuals were 0.845 (95% CI, 0.767-0.925), 0.770 (95% CI, 0.683-0.857), and 0.691 (95% CI, 0.593-0.789), respectively. Application of multivariable logistic regression resulted in the combination of CD4⁺ T cell non-specific function, NK cell non-specific function, and culture filtrate protein-10 (CFP-10) spot number as the optimally diagnostic model for differentiating ATB from LTBI. The AUC of the model in distinguishing between ATB and LTBI was 0.939 (95% CI, 0.898-0.981). The sensitivity and specificity were 83.67% (95% CI, 70.96%-91.49%) and 90.63% (95% CI, 81.02%-95.63%) with the threshold as 0.57. Our established model showed superior performance to TB-specific antigen (TBAg)/PHA ratio in stratifying TB infection status.

Conclusions

Lymphocyte non-specific function detection offers an attractive alternative to facilitate TB diagnosis. The three-index diagnostic model was proved to be a potent tool for the identification of different events involved in TB infection, which is helpful for the treatment and management of patients.

Combination of prealbumin and tuberculosis-specific antigen/phytohemagglutinin ratio for discriminating active tuberculosis from latent tuberculosis infection

BACKGROUND

Given that there is no rapid and effective method for distinguishing active tuberculosis (ATB) from latent tuberculosis infection (LTBI), the discrimination between these two statuses remains challenging. This study sought to investigate the value of nutritional indexes and tuberculosis-specific antigen/phytohemagglutinin ratio (TBAg/PHA ratio) for distinguishing ATB from LTBI.

METHODS

Participants were consecutively recruited based on positive T-SPOT.TB results between January 2018 and January 2020. ATB was diagnosed by positive mycobacterial culture and/or positive GeneXpert MTB/RIF, with clinical symptoms and radiological characteristics suggestive of ATB. Individuals with positive T-SPOT.TB but without the evidence of ATB were defined as LTBI. Patients younger than 17 years and undergoing anti-TB treatment were excluded.

RESULTS

A total of 709 (312 ATB and 397 LTBI) and another 309 (120 ATB and 189 LTBI) subjects were respectively recruited from Tongji Hospital (Qiaokou cohort) and Sino-French New City Hospital (Caidian cohort). The level of prealbumin was significantly lower in ATB than in LTBI. With a cut-off value of 139 mg/L, the sensitivity and specificity of prealbumin in distinguishing ATB from LTBI were 50.96% (45.41%-56.51%) and 91.69% (88.97%-94.40%). Meanwhile, TBAg/PHA ratio was found statistically higher in ATB compared with LTBI. If using the threshold of 0.29, the sensitivity and specificity of TBAg/PHA ratio were 65.71% (60.44%-70.97%) and 90.93% (88.11%-93.76%), respectively. Moreover, the combination of prealbumin and TBAg/PHA ratio (obtaining by diagnostic model) yielded better specificity (90.18%, [87.25%-93.10%]) and sensitivity (87.18%, [83.47%-90.89%]), while the clinical utility index (CUI) positive and CUI negative were respectively 0.76 and 0.81. After anti-TB treatment, TBAg/PHA ratio was declined while the level of prealbumin was restored (Wilcoxon test, P < 0.001). Furthermore, the performance of diagnostic model obtained in Qiaokou cohort was confirmed in Caidian cohort.

CONCLUSIONS

The diagnostic model based on combination of prealbumin and TBAg/PHA ratio is a rapid and accurate tool for discriminating ATB from LTBI.

Functional Component Isolated from Phaseolus vulgaris Lectin Exerts In Vitro and In Vivo Anti-Tumor Activity Through Potentiation of Apoptosis and Immunomodulation

Phytohemagglutinin (PHA), the lectin purified from red kidney bean (Phaseolus vulgaris), is a well-known mitogen for human lymphocyte. Because it has obvious anti-proliferative and anti-tumor activity, PHA may serve as a potential antineoplastic drug in future cancer therapeutics. However, the literature is also replete with data on detrimental effects of PHA including oral toxicity, hemagglutinating activity, and immunogenicity. There is a critical need to evaluate the functional as well as the toxic components of PHAs to assist the rational designs of treatment with it. In this report, we performed SDS-PAGE to identify components of PHA-L, the tetrameric isomer of PHA with four identical L-type subunits, and then characterized biological function or toxicity of the major protein bands through in vitro experiments. It was found that the protein appearing as a 130 kD band in SDS-PAGE gel run under the condition of removal of β-mercaptoethanol from the sample buffer together with omission of a heating step could inhibit tumor cell growth and stimulate lymphocyte proliferation, while most of the 35 kD proteins are likely non-functional impurity proteins and 15 kD protein may be related to hemolytic effect. Importantly, the 130 kD functional protein exhibits promising in vivo anti-tumor activity in B16-F10 melanoma C57 BL/6 mouse models, which may be achieved through potentiation of apoptosis and immunomodulation. Altogether, our results suggest that PHA-L prepared from crude extracts of red kidney bean by standard strategies is a mixture of many ingredients, and a 130 kD protein of PHA-L was purified and identified as the major functional component. Our study may pave the way for PHA-L as a potential anticancer drug.

Diagnostic Value of T-SPOT.TB Assay for Tuberculous Peritonitis: A Meta-Analysis

Background: Tuberculous peritonitis (TP) is a common form of abdominal tuberculosis (TB). Diagnosing TP remains challenging in clinical practice. The aim of the present meta-analysis was to evaluate the diagnostic accuracy of peripheral blood (PB) T-SPOT and peritoneal fluid (PF) T-SPOT for diagnosing TP.

Methods: PubMed, EmBase, Cochrane, Scopus, Google scholar, China national knowledge internet, and Wan-Fang databases were searched for relevant articles from August 1, 2005 to July 5, 2020. Statistical analysis was performed using Stata, Revman, and Meta-Disc software. Diagnostic parameters including pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were determined. Summary receiver operating characteristic curve was used to determine the area under the curve (AUC).

Results: Twelve studies were eligible and included in the meta-analysis. The analysis showed that the pooled sensitivity and specificity of PB T-SPOT in diagnosing TP were 0.91 (95% CI, 0.88–0.94) and 0.78 (95% CI, 0.73–0.81), respectively, while the pooled PLR, NLR, and DOR were 4.05 (95% CI, 2.73–6.01), 0.13 (95% CI, 0.07–0.23), and 37.8 (95% CI, 15.04–94.98), respectively. On the other hand, the summary estimates of sensitivity, specificity, PLR, NLR, and DOR of PF T-SPOT for TP diagnosis were 0.90 (95% CI, 0.85–0.94), 0.78 (95% CI, 0.72–0.83), 6.35 (95% CI, 2.67–15.07), 0.14 (95% CI, 0.09–0.21), and 58.22 (95% CI, 28.76–117.83), respectively. Furthermore, the AUC of PB T-SPOT and PF T-SPOT for TP diagnosis were 0.91 and 0.94, respectively.

Conclusions: Our results indicate that both PB T-SPOT and PF T-SPOT can be served as sensitive approaches for the diagnosis of TP. However, the unsatisfactory specificities of these two methods limit their application as rule-in tests for TP diagnosis. Furthermore, the standardization of the operating procedure of PF T-SPOT is further needed.

A combination of iron metabolism indexes and tuberculosis-specific antigen/phytohemagglutinin ratio for distinguishing active tuberculosis from latent tuberculosis infection

BACKGROUND

Discriminating active tuberculosis (ATB) from latent tuberculosis infection (LTBI) remains challenging. This study aimed to investigate a diagnostic model based on a combination of iron metabolism and the TB-specific antigen/phytohemagglutinin ratio (TBAg/PHA ratio) in T-SPOT.TB assay for differentiation between ATB and LTBI.

METHODS

A total of 345 participants with ATB (n=191) and LTBI (n=154) were recruited based on positive T-SPOT.TB results at Tongji hospital between January 2017 and January 2020. Iron metabolism analysis was performed simultaneously. A diagnostic model for distinguishing ATB from LTBI was established according to multivariate logistic regression.

RESULTS

The TBAg/PHA ratio showed 64.00% sensitivity and 90.10% specificity in distinguishing ATB from LTBI when a threshold of 0.22 was used. All iron metabolism biomarkers in the ATB group were significantly different from those in the LTBI group. Specifically, serum ferritin and soluble transferrin receptor in ATB were significantly higher than LTBI. On the contrary, serum iron, transferrin, total iron binding capacity, and unsaturated iron binding capacity in ATB were significantly lower than LTBI. The combination of iron metabolism indicators accurately predicted 60.00% of ATB cases and 91.09% of LTBI subjects, respectively. Moreover, the combination of iron metabolism indexes and TBAg/PHA ratio resulted in a sensitivity of 88.80% and specificity of 90.10%. Furthermore, the performance of models established in the Qiaokou cohort was confirmed in the Caidian cohort.

CONCLUSIONS

The data suggest that the combination of iron metabolism indexes and TBAg/PHA ratio could serve as a biomarker to distinguish ATB from LTBI in T-SPOT-positive individuals.

Combination of mean spot sizes of ESAT-6 spot-forming cells and modified tuberculosis-specific antigen/phytohemagglutinin ratio of T-SPOT.TB assay in distinguishing between active tuberculosis and latent tuberculosis infection

OBJECTIVES

Distinguishing between active tuberculosis (ATB) and latent tuberculosis infection (LTBI) remains challenging.

METHODS

The modified T-SPOT.TB assay was performed in 499 participants (243 ATB and 256 LTBI) and another 322 participants (162 ATB and 160 LTBI) who were diagnosed in Qiaokou (training) and Caidian (validation) cohort respectively.

RESULTS

The mean spot sizes (MSS) of early secreted antigenic target 6 (ESAT-6) spot-forming cells (SFC) of T-SPOT.TB assay in ATB patients was significantly higher than that in LTBI individuals. 1.0 × 10⁵ was the optimal number of cells added to phytohaemagglutinin (PHA) well for obtaining more accurate TB-specific antigen to phytohaemagglutinin (TBAg/PHA) ratio. The area under the curve of the diagnostic model by combination of ESAT-6 SFC MSS and modified TBAg/PHA ratio in distinguishing ATB from LTBI was 0.959 in training cohort, with a sensitivity of 90.12% and a specificity of 91.02% when a cutoff value of 0.46 was used. This diagnostic model showed similar performance in the validation cohort. The area under the curve, sensitivity, and specificity were 0.962, 93.21%, and 90.00%, respectively. Further flow cytometry analysis showed that ESAT-6 stimulation induced a significantly higher mean fluorescence intensity of IFN-γ⁺ cells in lymphocytes compared with culture filtrate protein 10 (CFP-10) stimulation. In contrast, CFP-10 stimulation induced a significantly higher percentage of IFN-γ⁺ cells in lymphocytes compared with ESAT-6 stimulation.

CONCLUSIONS

The combination of the MSS of ESAT-6 SFC and the modified TBAg/PHA ratio of T-SPOT.TB assay showed great value in discriminating ATB from LTBI.

Combination of Xpert MTB/RIF and TBAg/PHA Ratio for Prompt Diagnosis of Active Tuberculosis: A Two-Center Prospective Cohort Study

The prompt diagnosis of active tuberculosis (ATB) is still a challenge in clinical practice, especially in TB-endemic countries. We prospectively enrolled consecutive patients with suspected pulmonary TB from two tertiary hospitals. Acid-fast staining (AFS), Xpert MTB/RIF (Xpert), Mycobacterium tuberculosis culture, and T-SPOT.TB were simultaneously performed. 226 ATB and 348 non-TB patients were diagnosed in Tongji hospital (test cohort), and 86 ATB and 110 non-TB patients were diagnosed in Guangzhou Chest Hospital (validation cohort). Using ATB as patient group and non-TB as control group, for diagnosis of ATB in Tongji Hospital, the sensitivity of AFS was 17.70% (95% CI: 13.08–23.44%). The sensitivity of Xpert and culture were 53.54% (95% CI: 46.81–60.14%) and 46.46% (95% CI: 39.86–53.19%), respectively. The sensitivity of T-SPOT.TB was 81.42% (95% CI: 75.60–86.14%), but the specificity was 71.55% (95% CI: 66.60–76.04%). Calculation of the ratio of TB-specific antigen to phytohaemagglutinin (TBAg/PHA) of T-SPOT.TB assay increased the specificity but with a loss of sensitivity. Combination of Xpert and culture slightly increased the sensitivity compared to using these methods separately. Combination of Xpert and TBAg/PHA ratio (defined as Xpert positive or TBAg/PHA ≥ 0.2) increased diagnostic accuracy, and the sensitivity and specificity of combination of them were 85.84% (95% CI: 80.45–89.98%) and 95.98% (95% CI: 93.36–97.59%), respectively. The diagnostic model was also established based on combination of Xpert and TBAg/PHA ratio. The area under the curve of the diagnostic model was 0.952 (95% CI: 0.932–0.973) for diagnosis of ATB, with a sensitivity of 88.05% (95% CI: 83.10–91.98%) and a specificity of 96.26% (95% CI: 93.70–98.00%) when a cutoff value of 0.44 was used in Wuhan cohort. The performance of combination of Xpert and TBAg/PHA ratio was similar in Guangzhou Chest Hospital. Our data suggest that combination of Xpert and TBAg/PHA ratio may be a good algorithm for prompt diagnosis of ATB in high endemic areas.

Can Interferon-γ Release Assays Be Useful for Monitoring the Response to Anti-tuberculosis Treatment?: A Systematic Review and Meta-analysis

The number of studies which evaluated interferon-gamma release assays (IGRAs) results after anti-tuberculosis (TB) treatment has been rapidly increasing. The aim of this study was to investigate the potential use of IGRAs (QFT-GIT, T-SPOT.TB, QFT-Plus) in assessing the response to anti-TB treatment. We searched all studies in English language published from 1 October 2011 to 18 November 2018 in PubMed, Web of Science, and Scopus. Our search included the term "tuberculosis treatment AND interferon-γ release assay". We included studies evaluating the performance of commercial IGRAs (including QFT-GIT, T-SPOT.TB and QFT-Plus) before and after the anti-TB treatment. We performed subgroup analysis based on the age (children, adults), type of TB (active, latent, active and latent, and contacts exposed to MDR defined as MDR LTBI), type of IGRAs (QFT-GIT and T-SPOT.TB), and follow-up interval (2, 3, 4, 6, 9 months). Of the 18 included studies, 12 used QFT-GIT for assessment of IGRA performance after therapy, 1 used T-SPOT.TB, and 3 used both QFT-GIT and T-SPOT.TB. Since then, only two studies have assessed the QFT-Plus performance during therapy. According to the results of the meta-analysis, the pooled rate of positive IGRAs (QFT-GIT and T-SPOT.TB) following anti-TB therapy was estimated at 76% [95% CI 70-81%] and no difference was found compared to the pooled positive rate of IGRAs before initiation of therapy which was 76% [95% CI 60-89%]. The subgroup analysis showed that the pooled rate of positive IGRAs (QFT-GIT and T-SPOT.TB) after anti-TB therapy was significantly higher in monitoring active TB subjects [80% (95% CI 74-88%)] than LTBI [71% (95% CI 70-81%)]. Available data are now sufficient to suggest that monitoring changes in the IGRAs (QFT-GIT and T-SPOT.TB) response during anti-TB treatment may have limited use in evaluating the effectiveness of treatment, while the monitoring changes in QFT-Plus during anti-tubercular treatment are recommended to determine treatment efficacy or for treatment monitoring. Further research is needed to establish the efficacy of this new assay as marker on a larger scale for treatment monitoring.

The Performance of Pleural Fluid T-SPOT.TB Assay for Diagnosing Tuberculous Pleurisy in China: A Two-Center Prospective Cohort Study

The performance of T-SPOT.TB (T-SPOT) assay in diagnosing pleural tuberculosis (plTB) is inconsistent. In this study, we compared the performance of peripheral blood (PB) and pleural fluid (PF) T-SPOT assay in diagnosing plTB. Between July 2017 and March 2018, 218 and 210 suspected plTB patients were prospectively enrolled from Wuhan (training) and Guangzhou (validation) cohort, respectively. PB T-SPOT, PF T-SPOT, and other conventional tests were simultaneously performed. Our data showed the performance of PB T-SPOT in diagnosing plTB was limited, especially with low sensitivity. However, the results of early secreted antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10) in PF T-SPOT were significantly increased compared with those in PB T-SPOT in plTB patients. If using 76 as the cutoff value of MAX (the larger of ESAT-6 and CFP-10) in Wuhan cohort, the sensitivity and specificity of PF T-SPOT to diagnose plTB were 89.76 and 96.70%, respectively. The diagnostic accuracy of PF T-SPOT was better than other routine tests such as pathogen detection methods and biochemical markers. The diagnostic accuracy of PF T-SPOT in Guangzhou cohort was similar to that in Wuhan cohort, with a sensitivity and specificity of 91.07 and 94.90%, respectively. Furthermore, CD4⁺ T cells were more activated in PF compared with PB, and the frequency of mycobacterium tuberculosis-specific CD4⁺ T cells in PF was significantly higher than that in PB in plTB patients. In conclusion, the performance of PF T-SPOT is obviously better than PB T-SPOT or other laboratory tests, which suggests that PF T-SPOT assay has been of great value in the diagnosis of pleural tuberculosis.

Can we predict tuberculosis cure? What tools are available?

Antibiotic treatment of tuberculosis takes ≥6 months, putting a major burden on patients and health systems in large parts of the world. Treatment beyond 2 months is needed to prevent tuberculosis relapse by clearing remaining, drug-tolerant Mycobacterium tuberculosis bacilli. However, the majority of patients treated for only 2-3 months will cure without relapse and do not need prolonged treatment. Assays that can identify these patients at an early stage of treatment may significantly help reduce the treatment burden, while a test to identify those patients who will fail treatment may help target host-directed therapies.In this review we summarise the state of the art with regard to discovery of biomarkers that predict relapse-free cure for pulmonary tuberculosis. Positron emission tomography/computed tomography scanning to measure pulmonary inflammation enhances our understanding of "cure". Several microbiological and immunological markers seem promising; however, they still need a formal validation. In parallel, new research strategies are needed to generate reliable tests.