Diagnosis of Tuberculosis Following World Health Organization-Recommended Criteria in Severely Malnourished Children Presenting With Pneumonia

Advances in TB testing

Globally, tuberculosis (TB) was the leading cause of death from a single infectious agent until the coronavirus (COVID-19) pandemic. In 2020, an estimated 10 million people fell ill with TB and a total of 1.5 million people died from the disease. About one-quarter of the global population, almost two billion people, is estimated to be latently infected with Mycobacterium tuberculosis (MTB). Although latent TB infection (LTBI) is asymptomatic and noncontagious, about 5-10% of LTBI patients have a lifetime risk of progression to active TB. The diagnosis and treatment of active cases are extremely vital for TB control programs. However, achieving the End TB goal of 2035 without the ability to identify and treat the pool of latently infected individuals will be a big challenge. To do so, improved technology to provide more accurate diagnostic tools and accessibility are crucial. Therefore, this chapter covers the current WHO-endorsed tests and advances in diagnostic and screening tests for active and latent TB.

A systematic review of clinical, epidemiological and demographic predictors of tuberculosis in children with pneumonia

Background

Tuberculosis (TB) can present as acute, severe pneumonia in children, but features which distinguish TB from other causes of pneumonia are not well understood. We conducted a systematic review to determine the prevalence and to explore clinical and demographic predictors of TB in children presenting with pneumonia over three decades.

Methods

We searched for peer-reviewed, English language studies published between 1990 and 2020 that included children aged between 1 month and 17 years with pneumonia and prospectively evaluated for TB. There were 895 abstracts and titles screened, and 72 full text articles assessed for eligibility.

Results

Thirteen clinical studies, two autopsy studies and one systematic review were included in analyses. Majority of studies were from Africa (12/15) and included children less than five years age. Prevalence of bacteriologically confirmed TB in children with pneumonia ranged from 0.2% to 14.8% (median = 3.7%, interquartile range (IQR) = 5.95) and remained stable over the three decades. TB may be more likely in children with pneumonia if they have a history of close TB contact, HIV infection, malnutrition, age less than one year or failure to respond to empirical antibiotics. However, these features have limited discriminatory value as TB commonly presents as acute severe pneumonia – with a short duration of cough, and clinical and radiographic features indistinguishable from other causes of pneumonia. Approximately half of patients with TB respond to initial empirical antibiotics, presumably due to bacterial co-infection, and follow-up may be critical to detect and treat TB.

Conclusion

TB should be considered as a potential cause or comorbidity in all children presenting with pneumonia in high burden settings. Clinicians should be alert to the presence of known risk factors for TB and bacteriological confirmation sought whenever possible. Quality data regarding clinical predictors of TB in childhood pneumonia are lacking. Further, prospective research is needed to better understand predictors and prevalence of TB in childhood pneumonia, particularly in TB endemic settings outside of Africa and in older children. Children of all ages with pneumonia should be included in research on improved, point-of-care TB diagnostics to support early case detection and treatment.

Lipoarabinomannan Antigen Assay (TB-LAM) for Diagnosing Pulmonary Tuberculosis in Children with Severe Acute Malnutrition in Mozambique

BACKGROUND

Tuberculosis (TB) and malnutrition are important causes of morbidity and mortality in children in the developing world.

AIMS

To assess the prevalence of pulmonary TB in severely malnourished children and evaluate TB detection using the urine lipoarabinomannan antigen assay (TB-LAM).

METHODS

A retrospective analysis was conducted in all pediatric inpatients with severe acute malnutrition at a rural health center in Mozambique, from February to August 2018. All children underwent a physical examination and chest X-ray, and their nasopharyngeal aspirates and stool specimens were studied for mycobacterial culture and subjected to the Xpert MTB/RIF assay. TB-LAM tests were performed on urine.

RESULTS

Of 45 included cases, 17 (37.8%) were clinically diagnosed as pulmonary TB. None of these were detected by the Xpert MTB test; 4 (8.9%) nasopharyngeal aspirates were TB-culture positive. Seventeen patients (37.8%)-all clinically diagnosed with TB-tested positive on the TB-LAM, while 23 (51.1%) were negative. In 5 (11.1%), the urine LAM was not done.

CONCLUSION

Although our sample size was small, TB was diagnosed and treated in more than a third of included children. The urine TB-LAM test showed a perfect correlation with clinical diagnosis of childhood TB.

LAY SUMMARY

Severe acute malnutrition makes children more vulnerable to tuberculosis (TB) infections, but it is difficult to detect TB in children because they cannot always cough up phlegm, which is used in diagnostic processes. This study aimed to find out how many severely malnourished children had TB in Gaza, Mozambique, and to test the accuracy of a less-used diagnostic test: the lipoarabinomannan assay (TB-LAM). Of the 45 severely malnourished children who were admitted to our hospital, 17 were diagnosed with TB by their doctor. The TB-LAM corroborated the clinical diagnosis in all cases, while the other tests (Xpert MTB/RIF assay) and cultures failed to detect most of them. Overall, more than a third of severely malnourished children had TB, and the TB-LAM test-a simple, point-of-care method-was a highly accurate way to diagnose them. While larger studies are needed to confirm these results, our findings suggest that the TB-LAM could vastly improve TB diagnosis in malnourished children.

Impact of negative tuberculin skin test on growth among disadvantaged Bangladeshi children

Millions of children are suffering from tuberculosis (TB) worldwide and often end-up with fatal outcome especially in resource-poor settings. Tuberculin skin test (TST) is a conventionally used diagnostic test, less sensitive but highly specific for the diagnosis of clinical TB especially in undernourished children. However, we do not have any data on the role of TST positivity among the children who received nutritional intervention. Our aim was to examine the growth differences between TST-positive and TST-negative undernourished children aged 12 to 18 months who received nutritional intervention prospectively for 90 feeding days. Our further aim was to explore the determinants of TST positivity at enrollment. TB screening as one of the secondary causes of malnutrition was performed on 243 stunted [length for age Z score (LAZ) <-2 standard deviations] or at-risk of stunting (LAZ score between <-1 and -2 standard deviations) children in a community-based intervention study designed to improve their growth parameters. Differences of growth between TST-positives (n = 29) and TST-negatives (n = 214) were compared using paired samples t-test and multivariable linear regression from anthropometric data collected before and after nutritional intervention. Multivariable logistic regression was used to find out possible predictors of TST positivity using baseline sociodemographic data. Of the 243 children screened, 29 (11.9%) were TST-positive and 11 (4.5%) had clinically diagnosed pulmonary TB. Statistically significant improvement of LAZ and weight for age Z-score (WAZ) were observed among the TST-negative participants at the end of intervention period (p = 0.03 for LAZ and p = 0.01 for WAZ). However, we did not find any association between TST status and response to nutritional intervention in our multivariable linear regression models. Our study findings demonstrated a positive impact of nutritional intervention on growth parameters among TST-negative participants.