Tuberculosis in children-is PCR the diagnostic solution?

Tuberculosis in the paediatric population of Madrid in the last 26 years

INTRODUCTION

Tuberculosis (TB) continues to be a serious public health problem and establishing a definitive diagnosis among children is extremely challenging. Pulmonary tuberculosis is the most prevalent form, with children under the age of 2 years being at greatest risk of severe and disseminated forms. The aim of this study was to describe TB among children in Spain in recent years.

PATIENTS AND METHODS

A retrospective study of paediatric patients diagnosed with TB in two hospitals of the Community of Madrid over a 26-year period (1991-2017). Epidemiological and clinical variables, additional tests and treatments received were analysed.

RESULTS

170 children were included. The two most-affected age groups were infancy and adolescence. 42.9% of patients were immigrant children (South-America or Morocco). The main reasons for consultation were TB contact (20.6%) and fever (15.3%). At diagnosis, 61.8% of cases referred an epidemic environment, and 30.6% were asymptomatic. The Mantoux tuberculin skin test was positive in 92.2% of patients and IGRA was positive in 70.6%. Pulmonary TB was identified in 91.8% of children vs. 8.2% with extrapulmonary forms. Gastric juice culture was positive in 36.9% of cases and three strains resistant to isoniazid were isolated. All patients were cured without complications except one who died.

CONCLUSIONS

Pulmonary TB continues to be the most prevalent form among children and presumptive diagnosis (symptoms consistent with positive Mantoux test or suggestive X-ray) is the most common form of diagnosis. It is important to conduct a contact investigation in order to control the spread of TB.

Newer Diagnostic Tests and their Application in Pediatric TB

The diagnosis of childhood tuberculosis is a challenge due to the pauci-bacillary nature of infection and the difficulty in obtaining appropriate sample. In the past 2-3 decades, many new tests were introduced for the diagnosis of tuberculosis (TB) and some of them have been evaluated for their application in pediatric tuberculosis as well. There is an attempt to improve smear microscopy by introducing light-emitting diode (LED) fluorescence microscopy and there are also some automated digital microscopy platforms under evaluation. Introduction of automated liquid culture platform along with rapid molecular based identification methods have considerably reduced the time delay in mycobacterial culture. Recent addition of many nucleic acid amplification platforms like Amplicor PCR, Genprobe, Xpert MTB/Rif, line probe assays, loop mediated isothermal amplification etc are also been found to be useful. Latest techniques like microarray and gene sequencing are also being used in clinical laboratories with variable results. Indirect methods of TB diagnosis like T cell based assays including tuberculin skin test and interferon-gamma release assays have their role primarily in the diagnosis of latent TB. Biomarkers are the latest addition in the battery of TB diagnostic tests facilitating diagnosis using easily accessible samples like urine, blood and breath of patients. Many biomarkers are still under evaluation and some of them are found to have a potential role as promising diagnostic tests of future.

Review of literature on disseminated tuberculosis with emphasis on the focused diagnostic workup

Disseminated tuberculosis (TB) is a life-threatening disease resulting from the hematogenous spread of Mycobacterium tuberculosis. The diagnosis is challenging owing to its subtle nonspecific clinical presentation, which usually reflects the underlying organ involved. Besides, tools for confirmatory laboratory diagnosis are limited. Therefore, a high index of suspicion is required for early diagnosis. Miliary pattern on chest radiography is a common finding that has an important role in the early detection of the disease. Nevertheless, approximately 10%-15% of patients have normal chest radiography. Although abnormalities are present, basic hematologic and biochemical tests as well as tuberculin skin test are nonspecific for the diagnosis. Imaging studies are helpful adjunct tools for disseminated TB as they can help determine the involved sites and guide technicians to obtain appropriate specimens for diagnosis. Clinical confirmation of the diagnosis of disseminated TB is usually based on bacteriological or histological evidence. Response to first-line anti-TB drugs is good as evidenced by many reports. This review aims to present a current update on disseminated TB with emphasis on the diagnostic workup of this devastating condition.

Real time PCR in childhood tuberculosis: a valuable diagnostic tool

The present study was conducted to detect and quantitate Mycobacterium tuberculosis from various body fluid specimens of cases of tuberculosis by real time PCR technique and compare results with conventional PCR technique and culture. One hundred fifteen children (<18 y) with tuberculosis (diagnosed as per IAP guidelines) and 32 disease matched controls from the Department of Pediatrics, S.N. Medical College, Agra, were included in the study. Different body fluids (CSF, gastric aspirate, pleural fluid, ascitic fluid and lymph node aspirate) were subjected to culture, conventional PCR targeting insertion sequence 1S6110 and Real time PCR targeting 16srRNA of Mycobacterium tuberculosis. Real time PCR showed significantly better results than culture in all body fluids (p < 0.05). It was superior to conventional PCR in CSF (p < 0.05) but showed comparable results in gastric aspirate, pleural fluid, ascitic fluid and lymph node aspirate (p > 0.05). Hence, real time PCR is a promising diagnostic tool for childhood tuberculosis, particularly tubercular meningitis.

[Description of tuberculosis outbreak and usefulness of mediastinal ultrasound]

OBJECTIVES

Describe a school outbreak of tuberculosis and compare the features with other outbreaks. Propose mediastinal ultrasound as an aid in its diagnosis and monitoring.

PATIENTS AND METHODS

Retrospective descriptive study of the transmission of tuberculosis infection in a micro-epidemic. Infection criteria: Mantoux ≥ 5mm, asymptomatic patient, with normal radiological, microbiological and analytical studies. Disease criteria: Mantoux ≥ 5mm and any of the above pathological studies. Mediastinal ultrasound was used as a complementary method of chest radiography (CXR). Computed tomography (CT) as the combined result of ultrasound and CXR was inconclusive.

RESULTS

Seventeen out of 412 students were infected and 16 with tuberculosis disease. In addition, 4 out-school contacts were diagnosed of tuberculosis.

CLINICAL MANIFESTATIONS

one erythema nodosum, one Henoch-Schönlein purpura, twelve with cough and fever nine. CXR results in patients: 3 normal, 7 inconclusive, and 10 with the following findings: 2 pneumonia, 2 pulmonary atelectasis, 2 primary complexes, 4 patients only with lymphadenopathy. All patients with normal or indeterminate CXR showed mediastinal lymphadenopathy visualized on ultrasound but 3 demonstrated by CT. Microbiological isolation: 6 cases (31%).

CONCLUSIONS

The number of infected patients was higher compared to other outbreaks There is great variability in the diagnostic approach to tuberculosis micro-epidemics. It is complex to differentiate between infection and disease. The clinical, laboratory and CXR are nonspecific. There are patients with normal CXR, pathological ultrasound and microbiological isolation. Mediastinal ultrasound can play an important role in the diagnosis and management of tuberculosis disease.

Promising directions in the diagnosis of childhood tuberculosis

Estimates of the burden of childhood tuberculosis have been hampered by the lack of a reliable diagnostic test. Clinical scoring systems, radiological findings and tuberculin skin testing (the traditional methods used for diagnosis) are unreliable, particularly in the era of HIV. Microbiologic confirmation using induced sputum is feasible and has become increasingly important to define the burden of disease and to enable appropriate treatment. The availability of a rapid molecular diagnostic test (Xpert® MTB/RIF; Cepheid) is an important advance that can improve case detection in children and enable rapid detection of mycobacterial drug resistance. Xpert testing of two induced sputum specimens detected approximately 75% of children with culture-confirmed disease. Urine lipoarabinomannan has shown promise as a rapid diagnostic in a subgroup of HIV-infected severely immunocompromised adults, but there have been no data in children so far. Further research is needed to develop a rapid point-of-care, reliable and affordable diagnostic test for childhood tuberculosis that can be widely used.

Usefulness of thoracic CT to diagnose tuberculosis disease in patients younger than 4 years of age

BACKGROUND

There is controversy over the need of using thoracic CT (TCT) systematically for differentiating disease from tuberculosis infection in young children. This distinction is important when making a diagnosis of TB as the treatment changes from a single drug to a multidurug regimen with reported side-effects.

AIM

To determine the usefulness of using TCT to diagnose pulmonary tuberculosis (PTB) in patients younger than 4 years of age who have TB infection (IBI).

MATERIALS AND METHODS

After the simultaneous detection of four cases of PTB in children who attended the same class, a study on the contact among workers and children was carried out. One hundred sixteen children younger than 4 years and 20 adults were included. The tuberculin skin test (TST) was performed on all of them. CHEST XR (CXR) and TCT were performed on children with positive TST and three samples of gastric acid were taken. CXR and sputum testing were performed on adults with positive TST.

RESULTS

TST was positive in 28 children (24.1%). In 92.8% of children with positive TST and normal CXR, TCT showed features compatible with PTB. Out of the 28 children with positive TST, 27 (96.4%) were diagnosed with PTB and only one with latent TBI (4%).

CONCLUSIONS

In children younger than 4-year old with positive TST and normal CXR, it would be advisable to perform a TCT since the findings could change the diagnosis from TBI to TB disease.

Infantile pulmonary tuberculosis: the great mimic

PURPOSE

Infantile tuberculosis is common in developing countries and rarely presents as space occupying thoracic lesions mimicking congenital malformations. This case series reviews four such infants with varied presentations and their outcome.

METHODS

Four cases of infantile pulmonary/mediastinal tuberculosis that presented like congenital thoracic lesions are described. Details of demography, symptomatology, contact history, immunization status, provisional diagnosis, tuberculin testing, imaging, histopathology, final diagnosis, management and outcome were retrospectively collated and analyzed.

RESULTS

They were 4-6-month males, term-born and immunized. They presented with pneumonia/hyperactive airway disease since 2-12 weeks. One had a suspect and another a close tuberculous contact. The provisional diagnosis after imaging were infected congenital lung cyst, posterior mediastinal cyst and bronchopulmonary malformation. Two were tuberculin positive; none had gastric acid-fast bacilli. One underwent a pulmonary lobectomy for necrotic lung cyst; the second had a biopsy and drainage of a posterior mediastinal cyst that contained caseating material and was densely adherent to the esophagus. Surgical biopsy showed necrotizing granulomatous inflammation in both; one with acid-fast bacilli. Both succumbed to postoperative complications. The other two with tuberculous contacts who were managed with early antituberculous therapy, responded well and recovered uneventfully.

CONCLUSIONS

Infantile pulmonary/mediastinal tuberculosis may mimic congenital thoracic malformations. A review of contact history, investigations and imaging help to establish the tuberculous etiology, avoids surgical misadventures and prompts early antituberculous therapy to achieve a favorable outcome.

Diagnosis of pulmonary tuberculosis in children: new advances

The global burden of childhood pulmonary TB has been underappreciated, in part due to difficulties in obtaining microbiological confirmation of disease. Most HIV-uninfected children can be diagnosed using a combination of clinical and epidemiological features, tuberculin skin testing and chest radiography, as represented in different scoring systems. However, accurate microbiologic diagnosis has become increasingly important for timely use of effective treatment. Mycobacterial culture confirms the diagnosis of TB and provides drug susceptibility data but is not available in most areas with a high TB prevalence. Moreover, culture has poor sensitivity in children who usually have paucibacillary disease. The HIV epidemic has made definitive diagnosis even more challenging due to nonspecific clinical and radiological signs. In high HIV-prevalence areas, scoring systems have been especially variable, lacking sensitivity and specificity. Newer methods for diagnosis are aimed either at detecting the organism or a specific host immune response. Methods for organism detection have focused on collection of better samples, improved culture techniques, molecular methods or antigen detection. Recent advances include the use of sputum induction for obtaining a more reliable specimen, faster and more sensitive culture methods, and rapid detection of the organism and drug resistance based on nucleic acid amplification. Improved methods for detecting a specific host response have largely focused on the use of IFN-g release assays. Even with newer methods, accurately diagnosing childhood TB may be challenging. Greater efforts to obtain a microbiologic diagnosis should be made in children, even in primary care settings. Further research to develop a more accurate, cost-effective and simple diagnostic test for childhood TB is urgently needed.

[Diagnosis of tuberculosis in pediatrics. Consensus document of the Spanish Society of Pediatric Infectology (SEIP) and the Spanish Society of Pediatric Pneumology (SENP)]

Tuberculosis is one of the most important health problems worldwide. There are an increased number of cases, including children, due to different reasons in developed countries. The most likely determining cause is immigration coming from high endemic areas. Measures to optimize early and appropriate diagnosis of the different forms of tuberculosis in children are a real priority. Two Societies of the Spanish Pediatric Association (Spanish Society of Pediatric Infectology and Spanish Society of Pediatric Pneumology) have agreed this Consensus Document in order to homogenize diagnostic criteria in pediatric patients.

Clinical practice: diagnosis of childhood tuberculosis

Childhood tuberculosis (TB) represents an important part of the disease burden, yet its diagnosis remains challenging. This review summarizes the clinical, radiological, and bacteriological approaches to diagnose TB infection and disease in children. Fever (possibly intermittent or low grade), weight loss or failure to thrive, and a persistent cough for >2 weeks are the most important clinical signs for pulmonary tuberculosis. Extra-pulmonary TB, which might occur in over 40% of the patients, can have in addition some specific clinical symptoms or signs. Chest radiographs provide important information in many patients and advanced imaging can be applied in case of (and should be restricted to) inconclusive diagnosis. The Mantoux test is positive in up to 70% of non-immunocompromised TB patients, whereas HIV co-infection or malnourishment results in a lower reactivity. Evidence of an adult TB index case is clue for diagnosis of childhood TB in low-endemic countries. Bacteriological confirmation remains difficult and is useful for doubtful cases or when drug resistance is suspected.

Tuberculosis in children

Tuberculosis (TB) control poses one of the major global health challenges in the new millennium. Children in TB-endemic areas suffer severe TB related morbidity and mortality, despite the availability of cheap and effective TB treatment. However, providing an accurate TB diagnosis together with access to supervised, child friendly treatment remains difficult in resource-limited settings. This review provides a broad overview of recent advances related to child TB, focusing on intra-thoracic disease manifestations. It summarizes current understanding of TB epidemiology, disease prevention, diagnosis and treatment, but also introduces novel concepts for further discussion and future evaluation.

Recent advances in the diagnosis of childhood tuberculosis

Children account for a major proportion of the global tuberculosis disease burden, especially in endemic areas. However, the accurate diagnosis of childhood tuberculosis remains a major challenge. This review provides an overview of the most important recent advances in the diagnosis of intrathoracic childhood tuberculosis: (1) symptom-based approaches, including symptom-based screening of exposed children and symptom-based diagnosis of active disease; (2) novel immune-based approaches, including T cell assays and novel antigen-based tests; and (3) bacteriological and molecular methods that are more rapid and/or less expensive than conventional culture techniques for tuberculosis diagnosis and/or drug-resistance testing. Recent advances have improved our ability to diagnose latent infection and active tuberculosis in children, but establishing a diagnosis of either latent infection or active disease in HIV-infected children remains a major challenge, particularly in high-burden settings. Although improved access to diagnosis and treatment is essential, ultimately the burden of childhood tuberculosis is determined by the level of epidemic control achieved in a particular community. Several recent initiatives, in particular the United Nations Millennium Developmental Goals, deal with the problem of poverty and disease in a holistic fashion, but global political commitment is required to support these key initiatives.

Childhood Pulmonary Tuberculosis

Childhood tuberculosis is neglected in endemic areas with resource constraints, as children are considered to develop mild forms of disease and to contribute little to the maintenance of the tuberculosis epidemic. However, children contribute a significant proportion of the disease burden and suffer severe tuberculosis-related morbidity and mortality, particularly in endemic areas. This review provides an overview of well-documented concepts and principles, and demonstrates how this "old wisdom" applies to current and future challenges in the field of childhood tuberculosis; the aim was to articulate some of the most pressing issues, to provide a rational framework for discussion, and to stimulate thought and further scientific study. The prechemotherapy literature that described the natural history of disease in children identified three central concepts: (1) the need for accurate case definitions, (2) the importance of risk stratification, and (3) the diverse spectrum of disease pathology, which necessitates accurate disease classification. The relevance of these concepts and their application to pertinent issues such as the diagnosis of childhood tuberculosis are discussed. The concepts are also linked to the basic principles of antituberculosis treatment, providing a simplified approach to the diagnosis and treatment of childhood tuberculosis that is independent of resource constraints. The main challenges for future research are highlighted and in conclusion it is emphasized that the infrastructure provided by the directly observed therapy, short-course strategy, combined with well-targeted interventions, slightly improved resources, and greatly improved political commitment, may lead to a dramatic reduction in tuberculosis-related morbidity and mortality among children.

Confidence in polymerase chain reaction diagnosis can be improved by Bayesian estimation of post-test disease probability

OBJECTIVE

Polymerase chain reaction (PCR) techniques allow highly sensitive detection of specific DNA for diagnosis of infectious and genetic disease, but uncertainty relating to sensitivity and contamination has frequently resulted in controversy over results. We propose a new design in which the PCR contamination rate is estimated experimentally. The sensitivity of duplicate test results, and hence the post-test disease probabilities, can be derived algebraically, but wide confidence limits around these point estimates reduce their usefulness.

STUDY DESIGN AND SETTING

We have developed a Bayesian method which gives better estimates of post-test disease probability and can substantially reduce uncertainty by using the prior belief that sensitivity is not lower than 90%.

RESULTS

With 100 duplicate test samples and 100 control samples, we find that the post-test disease probability for concordant results (both positive or both negative) is generally unequivocal. The post-test disease probability for discordant results (one test positive and one negative) is often sufficiently clear to allow useful interpretation of individual test results, depending on the context.

CONCLUSION

Using this approach, the performance of a PCR can be evaluated experimentally allowing post-test disease probability to be estimated, giving improved confidence in test results.

Childhood tuberculosis and its early diagnosis

Traditional methods for laboratory diagnosis of tuberculosis are unsatisfactory, especially for children, in whose specimens mycobacteria are usually sparse. Recent changes in tuberculosis epidemiology in developed countries, including a large increase in incidence in children from certain ethnic minorities, have prompted interest in newer diagnostic methods. Liquid-based culture detection systems offer improved sensitivity and speed of diagnosis, although the time taken for detection of growth is still upwards of 1 week. Nucleic acid amplification techniques offer more rapid results, but perform best on smear-positive samples; sensitivities may be as low as 50% in smear-negative specimens. Although these newer techniques are widely used in some developed countries, in others, they are not perceived as offering sufficient benefit to justify their routine use. The diagnostic accuracy of mycobacteriophage and serologic methods is insufficient to justify their wide use even in developing countries. Despite recent developments, there is still no panacea for diagnosis of childhood tuberculosis.