Diagnostic potential of an enzyme-linked immunospot assay in tuberculous pericarditis

Diagnostic values of Xpert MTB/RIF, T-SPOT.TB and adenosine deaminase for HIV-negative tuberculous pericarditis in a high burden setting: a prospective observational study

The diagnosis of tuberculous pericarditis (TBP) remains challenging. This prospective study evaluated the diagnostic value of Xpert MTB/RIF (Xpert) and T-SPOT.TB and adenosine deaminase (ADA) for TBP in a high burden setting. A total of 123 HIV-negative patients with suspected TBP were enrolled at a tertiary referral hospital in China. Pericardial fluids were collected and subjected to the three rapid tests, and the results were compared with the final confirmed diagnosis. Of 105 patients in the final analysis, 39 (37.1%) were microbiologically, histopathologically or clinically diagnosed with TBP. The sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio and diagnostic odds ratio (DOR) for Xpert were 66.7%, 98.5%, 96.3%, 83.3%, 44.0, 0.338, and 130.0, respectively, compared to 92.3%, 87.9%, 81.8%, 95.1%, 7.6, 0.088, and 87.0, respectively, for T-SPOT.TB, and 82.1%, 92.4%, 86.5%, 89.7%, 10.8, 0.194, and 55.8, respectively, for ADA (≥ 40 U/L). ROC curve analysis revealed a cut-off point of 48.5 spot-forming cells per million pericardial effusion mononuclear cells for T-SPOT.TB, which had a DOR value of 183.8, while a cut-off point of 41.5 U/L for ADA had a DOR value of 70.9. Xpert (Step 1: rule-in) followed by T-SPOT.TB [cut-off point] (Step 2: rule-out) showed the highest DOR value of 252.0, with only 5.7% (6/105) of patients misdiagnosed. The two-step algorithm consisting of Xpert and T-SPOT.TB could offer rapid and accurate diagnosis of TBP.

Prospective comparison of two enzyme-linked immunosorbent spot assays for the diagnosis of Lyme neuroborreliosis

Commercial cellular tests are used to diagnose Lyme borreliosis (LB), but studies on their clinical validation are lacking. This study evaluated the utility of an in‐house and a commercial enzyme‐linked immunosorbent spot (ELISpot) assay for the diagnosis of Lyme neuroborreliosis (LNB). Prospectively, peripheral blood mononuclear cells (PBMCs) were isolated from patients and controls and analysed using an in‐house Borrelia ELISpot assay and the commercial LymeSpot assay. B. burgdorferi B31 whole cell lysate and a mixture of outer surface proteins were used to stimulate the PBMCs and the numbers of interferon‐gamma‐secreting T cells were measured. Results were evaluated using receiver operating characteristic (ROC) curve analysis. Eighteen active and 12 treated LNB patients, 10 healthy individuals treated for an early (mostly cutaneous) manifestation of LB in the past and 47 untreated healthy individuals were included. Both assays showed a poor diagnostic performance with sensitivities, specificities, positive and negative predictive values ranging from 44.4–66.7%, 42.0–72.5%, 21.8–33.3% and 80.5–87.0%, respectively. The LymeSpot assay performed equally poorly when the calculation method of the manufacturer was used. Both the in‐house and the LymeSpot assay are unable to diagnose active LNB or to monitor antibiotic treatment success.

Application Values of T-SPOT.TB in Clinical Rapid Diagnosis of Tuberculosis

BACKGROUND

This paper aims to explore the application value of tuberculosis-specific enzyme-linked immunospot assay (T-SPOT.TB) in the diagnosis of tuberculosis.

METHODS

Fifty one patients with tuberculosis (TB) admitted to Wuxi No.5 People's Hospital, Wuxi, China from June 2015 to June 2017 were selected as the TB group, and 40 patients without tuberculosis admitted in the same period were randomly selected as the non-TB group. Patients in the two groups received T-SPOT.TB, TB antibody (TB-Ab) test and mycobacterium TB deoxyribonucleic acid (TB-DNA) test, and the results were compared.

RESULTS

Comparisons of the sensitivity of the three methods showed that the sensitivity of T-SPOT.TB was the highest, followed by TB-DNA from sputum samples, and that of TB-Ab was the lowest. The specificity of TB-Ab was the highest, followed by T-SPOT.TB, and that of TB-DNA from sputum samples was the lowest. In the receiver operating characteristic (ROC) curve analysis, the area under curve (AUC) of T-SPOT.TB (0.896) was the highest, followed by TB-DNA from sputum samples (0.772), and that of sputum smears (0.698) was the lowest.

CONCLUSION

T-SPOT.TB can quickly and accurately determine the presence of tuberculosis infection, and it is a non-invasive examination, which can further assist in the diagnosis and guide the treatment.

Comparison between the diagnostic validities of Xpert MTB/RIF and interferon-γ release assays for tuberculous pericarditis using pericardial tissue

BACKGROUND

This study aimed to assess the diagnostic performance of Xpert MTB/RIF for tuberculous pericarditis (TBP) using pericardial tissues.

METHODS

The study involved 30 patients admitted with suspected TBP from January-December 2016; three patients were later excluded. The interferon-γ release assay (T-SPOT.TB) and the Xpert MTB/RIF test were performed using peripheral blood and pericardial tissues, respectively. TBP was confirmed using pericardial histopathology and a composite reference standard (CRS). We analyzed the sensitivity, specificity, predictive value (PV), likelihood ratio (LR), and area under curve (AUC) of both assays.

RESULTS

Fourteen patients were confirmed as TBP, 10 as non-TBP, and 3 as probable TBP. The sensitivity, specificity, positive PV (PPV), negative PV (NPV), PLR, NLR, and AUC (95% confidence interval [CI]) of the Xpert MTB/RIF assay were 78.6% (49.2-95.3%) and 70.6% (44.0-89.7%); 92.3% (64.0-99.8%) and 100% (69.2-100%); 91.7% (61.5-99.8%) and 100% (73.5-100%); 80.0% (51.9-95.7%) and 66.7% (38.4-88.2%); 10.21 (1.52-68.49) and the PLR value was undefined with CRS as the reference; 0.23 (0.08-0.64) and 0.29(0.14-0.61); and 0.854 (0.666-0.959) and 0.853 (0.664-0.959), against histopathology and CRS, respectively. The sensitivity, specificity, PPV, NPV, PLR, NLR, and AUC values (95% CI) of T-SPOT.TB were 92.9% (66.1-99.8%) and 94.1% (71.3-99.9%); 15.4% (1.9-45.5%) and 20.0% (2.5-55.6%); 54.2% (32.8-74.5%) and 66.7% (44.7-84.4%); 66.7% (9.4-99.2%) and 66.7% (9.4-99.2%); 1.10 (0.83-1.44) and 1.18 (0.84-1.6); 0.46 (0.05-4.53) and 0.29 (0.03-2.85); and 0.541(0.340-0.733) and 0.571(0.367-0.758), against histopathology and CRS, respectively. The differences in sensitivity, PPV, and AUC of Xpert MTB/RIF and T-SPOT.TB were not statistically significant (P > 0.05), compared to those of histopathology and CRS. However, the differences in specificity and NPV of the two assays were significant (P < 0.05), compared to those of histopathology and CRS.

CONCLUSIONS

Xpert MTB/RIF test is a valid diagnostic technique for TBP with higher sensitivity and specificity than T-SPOT.TB.

Towards standardized automated immunomonitoring: an automated ELISpot assay for safe and parallelized functionality analysis of immune cells

The ELISpot assay is used for the detection of T cell responses in clinical trials and vaccine evaluations. Standardization and reproducibility are necessary to compare the results worldwide, inter- and intra-assay variability being critical factors. To assure operator safety as well as high-quality experiment performance, the ELISpot assay was implemented on an automated liquid handling platform, a Tecan Freedom EVO. After validation of the liquid handling, automated loading of plates with cells and reagents was investigated. With step by step implementation of the manual procedure and liquid dispensing optimization on the robot platform, a fully automated ELISpot assay was accomplished with plates remaining in the system from the plate blocking step to spot development. The mean delta difference amounted to a maximum of 6%, and the mean dispersion was smaller than in the manual assay. Taken together, we achieved with this system not only a lower personnel attendance but also higher throughput and a more precise and parallelized analysis. This platform has the potential to guarantee validated, safe, fast, reproducible and cost-efficient immunological and toxicological assays in the future.

Diagnostic Value of Interferon-γ Release Assays on Pericardial Effusion for Diagnosis of Tuberculous Pericarditis

Diagnosis of tuberculous pericarditis remains a challenge. We aimed in this study to evaluate the diagnostic value of T-SPOT.TB on pericardial effusion for diagnosis of tuberculous pericarditis. Patients with suspected tuberculous pericarditis were enrolled consecutively between August 2011 and December 2015. T-SPOT.TB was performed on both pericardial effusion mononuclear cells (PEMCs)and peripheral blood mononuclear cells (PBMCs). Sensitivity, specificity, predictive value (PV), and likelihood ratio (LR) of T-SPOT.TB on PEMCs and PBMCs were analyzed. Among the 75 patients enrolled, 24 patients (32%) were diagnosed with tuberculous pericarditis, 38 patients (51%) with nontuberculous pericarditis, and 13 patients (17%) were clinically indeterminate and were excluded from the final analysis. The sensitivity, specificity, positive PV (PPV), negative PV (NPV), positive LR (LR+), and negative LR (LR-) of T-SPOT.TB on PEMCs was 92%,92%,88%,95%,11.61, and 0.09, respectively, compared to 83%, 95%, 91%, 90%,15.83, and 0.18, respectively of T-SPOT.TB on PBMCs. In patients with tuberculous pericarditis, the median frequencies of spot-forming cells (SFCs) of T-SPOT.TB on PEMCs and PBMCs was 172SFCs/106MCs (IQR 39~486), and 66 SFCs/106MCs (IQR 24~526), respectively, but the difference was not statistically significant (P = 0.183). T-SPOT.TB on PEMCs appeared to be a valuable and rapid diagnostic method for diagnosis of tuberculous pericarditis with high sensitivity and specificity.

Diagnosis and treatment of extrapulmonary tuberculosis

Extrapulmonary tuberculosis (EPTB) constitutes about 20% of all cases of tuberculosis (TB) in Korea. Diagnosing EPTB remains challenging because clinical samples obtained from relatively inaccessible sites may be paucibacillary, thus decreasing the sensitivity of diagnostic tests. Whenever practical, every effort should be made to obtain appropriate specimens for both mycobacteriologic and histopathologic examinations. The measurement of biochemical markers in TB-affected serosal fluids (adenosine deaminase or gamma interferon) and molecular biology techniques such as polymerase chain reaction may be useful adjuncts in the diagnosis of EPTB. Although the disease usually responds to standard anti-TB drug therapy, the ideal regimen and duration of treatment have not yet been established. A paradoxical response frequently occurs during anti-TB therapy. It should be distinguished from other causes of clinical deterioration. Surgery is required mainly to obtain valid diagnostic specimens and to manage complications. Because smear microscopy or culture is not available to monitor patients with EPTB, clinical monitoring is the usual way to assess the response to treatment.

Utility of T-cell interferon-γ release assays for diagnosing tuberculous serositis: a prospective study in Beijing, China

BACKGROUND

Diagnosis of tuberculous serositis remains a challenge. The aim of this study was to evaluate the diagnostic efficiency of T-SPOT.TB on serous effusion mononuclear cells (SEMC) for diagnosing tuberculous serositis in a high TB burden area.

METHODS

The present prospective study enrolled patients with suspected tuberculous serositis in a tertiary referral hospital in Beijing, China, to investigate the diagnostic sensitivity, specificity, predictive value (PV), and likelihood ratio(LR) of these tests. Clinical assessment, T-SPOT.TB on SEMC, and T-SPOT.TB on PBMC were performed. Test results were compared with the final confirmed diagnosis.

RESULTS

Of the 187 participants, 74 (39.6%) were microbiologically or clinically diagnosed as tuberculous serositis and 93(49.7%) were ruled out. The remaining 20 (10.7%) patients were clinically indeterminate and excluded from the final analysis. Compared to that on PBMC, T-SPOT.TB on SEMC showed higher sensitivity (91.9%vs73.0%, P = 0.002), specificity (87.1%vs.73.1%, P = 0.017), PPV (85.0%vs.68.4%, P = 0.013), NPV (93.1%vs.77.3%, P = 0.003), LR+ (7.12vs.2.72) and LR- (0.09vs.0.37), respectively. The frequencies of spot forming cells (SFCs) for T-SPOT.TB on SEMC were 636 per million SEMC (IQR, 143-3443) in patients with tuberculous serositis, which were 4.6-fold (IQR, 1.3-14.3) higher than those of PBMC. By ROC curve analysis, a cut-off value of 56 SFCs per million SEMC for T-SPOT.TB on SEMC showed a sensitivity of 90.5% and specificity of 89.2% for the diagnosis of tuberculous serositis.

CONCLUSIONS

T-SPOT.TB on SEMC could be an accurate diagnostic method for tuberculous serositis in TB endemic settings. And 56 SFCs per million SEMC might be the optimal cut-off value to diagnose tuberculous serositis.

Immunospot assay based on fluorescent nanoparticles for Dengue fever detection

Dengue fever is one of the most neglected tropical diseases and of highest international public health importance, with 50 million cases worldwide every year. Early detection can decrease mortality rates from more than 20% to less than 1% and the relevant early diagnosis analyte is the viral non-structural glycoprotein, NS1. Currently, enzyme linked immunosorbent assay (ELISA) is the method of choice to detect NS1. However, this is a time consuming method, requiring 3-5h, and it is the bottleneck for routine of clinical analysis laboratory in epidemic periods, when hundreds of samples should be tested. Here we describe an easy method combining principles of fluorophore linked immunosorbent assay (FLISA) and enzyme linked immunospotting (ELISPOT). For detection, we used mouse anti-NS1 IgG labeled with fluorescent nanoparticles. The presented procedure needs only 4 μL of serum samples and requires 45-60 min. The detection limit, 5.2 ng/mL, is comparable to ELISA tests. The comparison of 83 samples with a commercial ELISA revealed a sensitivity of 81% and specificity of 88%. The use of fluorescent nanoparticles provides a higher sensitivity than an assay using usual fluorescent dye molecules, besides avoiding bleaching effects. Based on the results, the proposed method provides fast, specific and sensitive results, and proves to be a suitable method for Dengue NS1 detection in impoverished regions or epidemic areas.

HIV-1 infection alters CD4+ memory T-cell phenotype at the site of disease in extrapulmonary tuberculosis

HIV-1-infected people have an increased risk of developing extrapulmonary tuberculosis (TB), the immunopathogenesis of which is poorly understood. Here, we conducted a detailed immunological analysis of human pericardial TB, to determine the effect of HIV-1 co-infection on the phenotype of Mycobacterium tuberculosis (MTB)-specific memory T cells and the role of polyfunctional T cells at the disease site, using cells from pericardial fluid and blood of 74 patients with (n=50) and without (n=24) HIV-1 co-infection. The MTB antigen-induced IFN-γ response was elevated at the disease site, irrespective of HIV-1 status or antigenic stimulant. However, the IFN-γ ELISpot showed no clear evidence of increased numbers of antigen-specific cells at the disease site except for ESAT-6 in HIV-1 uninfected individuals (p=0.009). Flow cytometric analysis showed that CD4⁺ memory T cells in the pericardial fluid of HIV-1-infected patients were of a less differentiated phenotype, with the presence of polyfunctional CD4⁺ T cells expressing TNF, IL-2 and IFN-γ. These results indicate that HIV-1 infection results in altered phenotype and function of MTB-specific CD4⁺ T cells at the disease site, which may contribute to the increased risk of developing TB at all stages of HIV-1 infection.