Diagnostic value of an enzyme-linked immunospot assay for interferon-γ in cutaneous tuberculosis

Screening for Latent Tuberculosis Infection in Adults: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force

Importance

Latent tuberculosis infection (LTBI) can progress to active tuberculosis disease, causing morbidity and mortality.

Objective

To review the evidence on benefits and harms of screening for and treatment of LTBI in adults to inform the US Preventive Services Task Force (USPSTF).

Data Sources

PubMed/MEDLINE, Cochrane Library, and trial registries through December 3, 2021; references; experts; literature surveillance through January 20, 2023.

Study Selection

English-language studies of LTBI screening, LTBI treatment, or accuracy of the tuberculin skin test (TST) or interferon-gamma release assays (IGRAs). Studies of LTBI screening and treatment for public health surveillance or disease management were excluded.

Data Extraction and Synthesis

Dual review of abstracts, full-text articles, and study quality; qualitative synthesis of findings; meta-analyses conducted when a sufficient number of similar studies were available.

Main Outcomes and Measures

Screening test accuracy; development of active tuberculosis disease, transmission, quality of life, mortality, and harms.

Results

A total of 113 publications were included (112 studies; N = 69 009). No studies directly evaluated the benefits and harms of screening. Pooled estimates for sensitivity of the TST were 0.80 (95% CI, 0.74-0.87) at the 5-mm induration threshold, 0.81 (95% CI, 0.76-0.87) at the 10-mm threshold, and 0.60 (95% CI, 0.46-0.74) at the 15-mm threshold. Pooled estimates for sensitivity of IGRA tests ranged from 0.81 (95% CI, 0.79-0.84) to 0.90 (95% CI, 0.87-0.92). Pooled estimates for specificity of screening tests ranged from 0.95 to 0.99. For treatment of LTBI, a large (n = 27 830), good-quality randomized clinical trial found a relative risk (RR) for progression to active tuberculosis at 5 years of 0.35 (95% CI, 0.24-0.52) for 24 weeks of isoniazid compared with placebo (number needed to treat, 112) and an increase in hepatotoxicity (RR, 4.59 [95% CI, 2.03-10.39]; number needed to harm, 279). A previously published meta-analysis reported that multiple regimens were efficacious compared with placebo or no treatment. Meta-analysis found greater risk for hepatotoxicity with isoniazid than with rifampin (pooled RR, 4.22 [95% CI, 2.21-8.06]; n = 7339).

Conclusions and Relevance

No studies directly evaluated the benefits and harms of screening for LTBI compared with no screening. TST and IGRAs were moderately sensitive and highly specific. Treatment of LTBI with recommended regimens reduced the risk of progression to active tuberculosis. Isoniazid was associated with higher rates of hepatotoxicity than placebo or rifampin.

Mandibular Nodule Caused by Mycobacterium marinum with False Positive Interferon-γ Release Assay. A Case Report

Mycobacterium marinum is a ubiquitous organism inhabiting both fresh and salt water. It can cause human diseases such as skin and soft tissue infection. The organism is also known to cause a false positive reaction to interferon-γ release assay, the test to diagnose latent tuberculosis infection. Here, we present a case of submandibular nodule caused by M. marinum with positive T-SPOT.TB test, which was likely to be false positive.

Delayed diagnosis and comprehensive treatment of cutaneous tuberculosis: A case report

BACKGROUND

Tuberculosis (TB) is a widespread infectious disease, with an incidence that is increasing worldwide. Cutaneous TB (CTB) occurs rarely, accounting for less than 1% of all TB cases. Due to the clinical presentation and diagnostic difficulties, CTB is often clinically neglected and misdiagnosed.

CASE SUMMARY

A 32-year-old man underwent several debridement surgeries and skin flap transplantation after trauma. The wound remained unhealed, accompanied by sinus formation. According to empirical judgment, T-cell spot of TB test, and bacterial culture of pyogenic fluids, he was diagnosed with CTB due to infection with exogenous Mycobacterium tuberculosis. A comprehensive anti-TB regimen that included isoniazid, rifampicin, ethambutol, and pyrazinamide was applied. The sinus was filled with a hydrophilic fiber-containing silver dressing, and wound-protecting sponges were applied to part of the wound. The wound healed after 40 d. No ulceration was found within 2 mo after discharge; further follow-up will be conducted.

CONCLUSION

A non-healing wound may be caused by TB infection. Comprehensive treatment of CTB is effective.

Cutaneous Mycobacterial Infections

Humans encounter mycobacterial species due to their ubiquity in different environmental niches. In many individuals, pathogenic mycobacterial species may breach our first-line barrier defenses of the innate immune system and modulate the activation of phagocytes to cause disease of the respiratory tract or the skin and soft tissues, sometimes resulting in disseminated infection. Cutaneous mycobacterial infections may cause a wide range of clinical manifestations, which are divided into four main disease categories: (i) cutaneous manifestations of Mycobacterium tuberculosis infection, (ii) Buruli ulcer caused by Mycobacterium ulcerans and other related slowly growing mycobacteria, (iii) leprosy caused by Mycobacterium leprae and Mycobacterium lepromatosis, and (iv) cutaneous infections caused by rapidly growing mycobacteria. Clinically, cutaneous mycobacterial infections present with widely different clinical presentations, including cellulitis, nonhealing ulcers, subacute or chronic nodular lesions, abscesses, superficial lymphadenitis, verrucous lesions, and other types of findings. Mycobacterial infections of the skin and subcutaneous tissue are associated with important stigma, deformity, and disability. Geography-based environmental exposures influence the epidemiology of cutaneous mycobacterial infections. Cutaneous tuberculosis exhibits different clinical phenotypes acquired through different routes, including via extrinsic inoculation of the tuberculous bacilli and dissemination to the skin from other sites, or represents hypersensitivity reactions to M. tuberculosis infection. In many settings, leprosy remains an important cause of neurological impairment, deformity, limb loss, and stigma. Mycobacterium lepromatosis, a mycobacterial species related to M. leprae, is linked to diffuse lepromatous leprosy of Lucio and Latapí. Mycobacterium ulcerans produces a mycolactone toxin that leads to subcutaneous tissue destruction and immunosuppression, resulting in deep ulcerations that often produce substantial disfigurement and disability. Mycobacterium marinum, a close relative of M. ulcerans, is an important cause of cutaneous sporotrichoid nodular lymphangitic lesions. Among patients with advanced immunosuppression, Mycobacterium kansasii, the Mycobacterium avium-intracellulare complex, and Mycobacterium haemophilum may cause cutaneous or disseminated disease. Rapidly growing mycobacteria, including the Mycobacterium abscessus group, Mycobacterium chelonei, and Mycobacterium fortuitum, are increasingly recognized pathogens in cutaneous infections associated particularly with plastic surgery and cosmetic procedures. Skin biopsies of cutaneous lesions to identify acid-fast staining bacilli and cultures represent the cornerstone of diagnosis. Additionally, histopathological evaluation of skin biopsy specimens may be useful in identifying leprosy, Buruli ulcer, and cutaneous tuberculosis. Molecular assays are useful in some cases. The treatment for cutaneous mycobacterial infections depends on the specific pathogen and therefore requires a careful consideration of antimicrobial choices based on official treatment guidelines.

Cutaneous Tuberculosis

Cutaneous tuberculosis (TB) may present in various clinical manifestations. Skin involvement may occur as a result of exogenous inoculation, contiguous spread from a nearby focus of infection, or by hematogenous spread from a distant focus. Because the clinical presentation of cutaneous TB can vary widely, it is important to have a high index of suspicion in appropriate clinical settings. In this chapter, the various clinical manifestations of clinical TB are classified by source of infection (exogenous, endogenous, and hematogenous spread). These are linked to the clinical appearance and histology of the skin lesions. Hopefully, this will resolve the confusion created by the myriad of terms previously used in the medical literature. Once a diagnosis of cutaneous TB is entertained, a biopsy for both culture and histopathology should be submitted. In some cases histopathology may show nonspecific inflammation without classic granuloma formation. In these cases, monoclonal antibodies and polymerase chain reaction (PCR) testing may be useful. In fact, in recent years, PCR amplification has proven to be invaluable in assisting identification of M. tuberculosis from skin biopsies in patients with negative TB cultures. In most instances, treatment of cutaneous TB requires combination chemotherapy. This is especially important in patients with extra cutaneous disease, multiple skin lesions, and those with profound immunosuppression. Surgery also may play both a diagnostic and therapeutic role.

An unusual perineal plaque

We present the case of a 61-year-old male with a long-standing perineal and scrotal lesion. Investigations eventually revealed cutaneous tuberculosis, with complete resolution after appropriate treatment. It highlights the variable presentation of cutaneous tuberculosis and the importance of considering the diagnosis in chronic lesions.

Cutaneous tuberculosis: diagnosis, histopathology and treatment - part II

The evolution in the knowledge of tuberculosis' physiopathology allowed not only a better understanding of the immunological factors involved in the disease process, but also the development of new laboratory tests, as well as the establishment of a histological classification that reflects the host's ability to contain the infectious agent. At the same time, the increasing bacilli resistance led to alterations in the basic tuberculosis treatment scheme in 2009. This article critically examines laboratory and histological investigations, treatment regimens for tuberculosis and possible adverse reactions to the most frequently used drugs.

Evaluation of an enzyme-linked immunospot assay for the immunodiagnosis of atypical spinal tuberculosis (atypical clinical presentation/atypical radiographic presentation) in China

Background

Methods

Results

Conclusions

Interferon-gamma release assays for the diagnosis of extrapulmonary tuberculosis: a systematic review and meta-analysis

Interferon -gamma release assays (IGRAs) provide a new diagnostic method for Mycobacterium tuberculosis (TB) infection. However, the diagnostic value of IGRAs for extrapulmonary TB (EPTB) has not been clarified. We searched several databases and selected papers with strict inclusion criteria, evaluated the evidence of commercially available IGRAs (QuantiFERON(®) -TB Gold QFT-G or QFT-GIT and T-SPOT(®) .TB) on blood and the tuberculin skin test (TST) using random effects models. Twenty studies with 1711 patients were included. After excluding indeterminate results, pooled sensitivity for the diagnosis of EPTB was 72% [95% confidence interval (CI) 65-79%] for QFT-G or GIT and 90% (95% CI, 86-93%) for T-SPOT; in high-income countries the sensitivity of QFT-G or GIT (79%, 95% CI 72-86%) was much higher than that (29%, 95% CI 14-48%) in low/middle-income countries. Pooled specificity for EPTB was 82% (95% CI 78-87%) for QFT-G or GIT and 68% (95% CI 64-73%) for T-SPOT. Pooled sensitivity of TST from four studies in high-income countries was lower than that of IGRAs. T-SPOT was more sensitive in detecting EPTB than QFT-G or GIT and TST. However, both IGRAs and TST have similar specificity for EPTB. IGRAs have limited value as diagnostic tools to screen and rule out EPTB, especially in low/middle-income countries. The immune status of patients does not affect the diagnostic accuracy of IGRAs for EPTB.