Effect of time, temperature and pH on Mycobacterium tuberculosis culture positivity of gastric aspirate: An experimental study

BACKGROUND

The culture of gastric aspirate (GA) has been used for bacteriological confirmation of pulmonary tuberculosis in children and patients who are unable to expectorate. Sodium bicarbonate neutralization of gastric aspirates is commonly recommended to increase culture positivity. We aim to study Mycobacterium tuberculosis (MTB) culture positivity of GA collected from confirmed case of pulmonary tuberculosis after storing it at different temperature, pH & time.

METHODS

GA specimens from 865 patients of either sex predominately non-expectorating children/adults with suspected pulmonary TB were collected. Gastric lavage was performed in the morning after an overnight fasting (at least 6hrs fasting). The GA specimens were tested by CBNAAT (GeneXpert) and AFB microscopy & those who were positive on CBNAAT were further processed with MTB culture on Growth Indicator Tube (MGIT™) culture. pH neutralized and non-neutralized CBNAAT positive GA specimens were culture within 2 hours of collection and 24 hours after storage at 4 °C & room temperature.

RESULTS

MTB was detected in 6.8% of collected GA specimens by CBNAAT. Culture positivity of neutralized GA specimens when processed within 2 hours of collection, was higher compared to paired non-neutralized GA specimens. Neutralized GA specimens had higher contamination rate than non-neutralized GA specimens. Storage of GA specimens at $Deg C had better culture yield than those stored at room temperature.

CONCLUSION

Early neutralization of acid in Gastric aspirate (GA) is essential for better culture positivity of M. tuberculosis (MTB). If there is a delay in processing GA, it should be kept at 4 °C after neutralization; however, positivity decreases with time.

Quality assurance of paediatric lateral chest radiographs

INTRODUCTION

Lateral chest radiographs aid in paediatric clinical practice in countries where the diagnosis of primary pulmonary tuberculosis (PTB) still relies heavily on the chest radiograph. This study aimed to create a validated quality assurance (QA) tool investigating the diagnostic performance of this projection by applying this to a database of lateral chest radiographs in children with suspected PTB.

METHOD

The QA tool was built to include a compilation of criteria from the different sources, accompanied by graphic representations and objective measurements where appropriate. Each defined criterion (radiographic error) was evaluated by implementing the QA tool on 300 radiographs, scored by three readers. The sample was subjected to two separate sets of data analysis, based on averages, and on majority decision methodology.

RESULTS

The QA tool was based on existing published criteria, as well as under-collimation and under-inspiration, two de novo criteria. For the total 900 reads, errors were categorized as patient-related in 681 (75.7%) and radiographer-related in 421 (46.8%) and 122 (13.6%) had no errors. The average number of errors per radiograph ranged from 0.9 to 4.7 errors out of the 11 quality factors reviewed. When considering the majority decision, the median errors per radiograph was 1 (IQR 1-2) (range 0-5). Inter-rater agreement varied for different criteria.

CONCLUSION

A novel QA tool for evaluating lateral chest radiographs was developed which requires further efforts of refinement regarding criteria such as exposure, field of view: under-collimation, and motion artifact, which remain subjective. The designed QA tool will allow comparison of radiograph quality before and after interventions. Furthermore, the tool can be used in tackling childhood PTB in low- and middle-income countries (LMICs) since the hallmark of the disease is lymphadenopathy, which is often depicted best on lateral chest radiographs.

Utility of RNTCP (NTEP) guidelines in microbiological confirmation of pediatric tuberculosis

OBJECTIVE

To estimate the proportion of microbiologically confirmed disease among children diagnosed with tuberculosis using RNTCP guidelines.

MATERIALS AND METHODS

Retrospective chart review of a cohort of 151 children (aged between 1 month and 18 years) diagnosed with Tuberculosis between December 2016 and June 2020 at a pediatric department of a tertiary care hospital. We collected information on AFB (Acid Fast Bacillus) smear and Cartridge Based Nucleic Acid Amplification Test (CB NAAT) results.

RESULTS

Out of 151 children with a diagnosis of Tuberculosis, 66 (44%) children were found to have microbiologically confirmed disease. Confirmatory rate was almost equal in children less than <5 and >5 years (48% vs 52%). Confirmatory rate did not differ between pulmonary and extra pulmonary samples (49% and 53%). Cartridge Based Nucleic Acid Amplification Test outperformed AFB by 10%, which was statistically significant (p = .000 by fisher exact test).

CONCLUSION

Although considered paucibacillary in nature, microbiological confirmation can be obtained in almost up to half of children with a diagnosis of TB by using RNTCP guidelines. Neither young age nor type of TB is a deterrent to bacteriologically confirm TB in children.

Xpert MTB/RIF assay can be used on archived gastric aspirate and induced sputum samples for sensitive diagnosis of paediatric tuberculosis

BACKGROUND

Tuberculosis (TB) in children is neglected, mainly due to lack of sensitive diagnostic tools. Recently Xpert MTB/RIF assay has revolutionized the diagnostic field, but its usefulness in pediatric TB has not been reported from India and no report is available on its use on long term archived samples.

METHODS

We recruited 130 pediatric patients with probable intrathoracic tuberculosis and their gastric aspirate (GA) and induced sputum (IS) samples on 2 consecutive days were collected between January 2009 and December 2012. All samples (n = 520) were subjected to smear examination, BACTEC-MGIT culture and in-house multiplex PCR. An aliquot of each sample was stored at -80 °C and tested in Xpert MTB/RIF assay in 2013.

RESULTS

Sample wise and patient wise detection rate of smear microscopy was 4.4 % and 10 %, while for BACTEC-MGIT culture this rate was 24.4 % and 46.9 %, respectively. Of the 130 day 1 GA samples, 31.5 % and 27.7 % day 2 GA samples were culture positive. Only 17.7 % GA samples were positive on both days. Of the 130 IS samples collected on day 1 and day 2, 15.4 % and 23.1 % samples were culture positive. A combination of GA and IS yielded best results. Combining both GA and IS, the overall sensitivity of Xpert MTB/RIF on smear and culture positive samples was 95.6 %. In smear negative and culture positive samples its sensitivity was 62.5 %. The duration of sample storage impacted the Xpert MTB/RIF test performance (p = 0.0001). In smear positive samples stored for 650-849 days, its sensitivity was 85.7 % and 77.1 % for IS and GA samples which dropped to 33.3 % and 50 %, respectively, if stored for more than 1050 days.

DISCUSSION

Confirmatory diagnosis of tuberculosis particularly in children is a medical challenge. No laboratory or radiological test can reach to a satisfactory level of diagnostic sensitivity. However, in this study we found that combination of multiple samples and multiple diagnostic tests can give much better yield, though not optimum. In present study, combination of 2 gastric aspirates (GA) and 2 induced sputum (IS) samples collected on two consecutive days, and tested on three diagnostic methods yielded a significantly high detection rate. Despite long term storage, the overall sensitivity of Xpert MTB/RIF on smear and -culture positive samples remained very high. But after storing these samples under subfreezing conditions the sensitivity of Xpert MTB/RIF decreased significantly. This is expected because even if the sample is smear and culture positive, the count of surviving mycobacteria goes down, after several years this count can reach to a undetectable level.

CONCLUSION

This report shows that smear and culture positive samples stored at subfreezing conditions for several years can be used in the Xpert MTB/RIF assay, while maintaining appreciable diagnostic test sensitivity and specificity.

Trends in childhood tuberculosis in Zambia: a situation analysis

OBJECTIVES

To ascertain childhood tuberculosis (TB) trends, human immunodeficiency virus (HIV) co-infection rates and multi-drug resistant TB (MDR-TB) prevalence rates in Zambia.

METHODS

A retrospective review of Zambian annual TB notification data and National TB Programme reports for a 7 year period (2004-2011). TB trends were stratified by age and HIV status.

RESULTS

The total number of children notified during this period with all forms of TB was 40 976. A total of 2670 of 40 976 (6%) were smear-positive cases. Notification rates of all forms of childhood TB show a decline in trends from 135 per 100 000 population in 2004, to 69 per 100 000 population in 2011.

CONCLUSIONS

Childhood TB is an important but neglected problem in Zambia highlighted by the fact that no data exists on HIV co-infection and MDR-TB. Strengthening of the National TB Programme and diagnostics services/algorithms are required to accurately define the TB burden, HIV co-infection and MDR-TB rates in children in Zambia.

Prevention, diagnosis, and treatment of tuberculosis in children and mothers: evidence for action for maternal, neonatal, and child health services

Tuberculosis affected an estimated 8.8 million people and caused 1.4 million deaths globally in 2010, including a half-million women and at least 64 000 children. It also results in nearly 10 million cumulative orphans due to parental deaths. Moreover, it causes 6%-15% of all maternal mortality, which increases to 15%-34% if only indirect causes are considered. Increasingly, more women with tuberculosis are notified than men in settings with a high prevalence of human immunodeficiency virus (HIV), and maternal tuberculosis increases the vertical transmission of HIV. Tuberculosis prevention, diagnosis, and treatment services should be included as key interventions in the integrated management of pregnancy and child health. Tuberculosis screening using a simple clinical algorithm that relies on the absence of current cough, fever, weight loss, and night sweats should be used to identify eligible pregnant women living with HIV for isoniazid preventive therapy or for further investigation for tuberculosis disease as part of services for prevention of vertical HIV transmission. While implementing these simple, low-cost, effective interventions as part of maternal, neonatal, and child health services, the unmet basic and operational tuberculosis research needs of children, pregnant, and breastfeeding women should be addressed. National policy makers, program managers, and international stakeholders (eg, United Nations bodies, donors, and implementers) working on maternal, neonatal, and child health, especially in HIV-prevalent settings, should give due attention and include tuberculosis prevention, diagnosis, and treatment services as part of their core functions and address the public health impacts of tuberculosis in their programs and services.

Are children with tuberculosis in Pakistan managed according to National programme policy guidelines? A study from 3 districts in Punjab

BACKGROUND

The adherence to policies of National TB Control Programme (NTP) to manage a case of tuberculosis (TB) is a fundamental step to have a successful programme in any country. Childhood TB services faces an unmet challenge of case management due to difficulty with diagnosis and relatively new policies. For control of childhood TB in Pakistan, NTP developed and piloted its guidelines in 2006-2007. The objective of this study was to compare the documented case management practices of pediatricians and its impact on the outcome before and after introducing NTP policy guidelines.

FINDINGS

An audit of case management practices of a historical cohort study was done in children below 15 years who were put on anti-tuberculosis treatment at all nine public hospitals in three districts in province of Punjab. The study period was two years pre-intervention (2004-05) and two years post-intervention (2006-07) after implementation of new NTP policy guidelines for childhood TB. There were 920 childhood TB cases registered during four years, 189 in pre-intervention period and 731 in post-intervention period. The practices changed significantly in post-intervention period for use of tuberculin skin test (63% of pulmonary cases, 19% of extrapulmonary cases and 67% for site unknown), and for the use of chest x-ray (69% of pulmonary cases, 16% of extrapulmonary cases and 74% for site unknown). Diagnostic scores were recorded for only a minority of cases (18%). The proportion of correct drugs pre- and post-intervention remained same. There were unknown treatment outcomes in 38 out of 141 cases (27%) in pre-intervention and in 483 out of 551 cases (87%) post-intervention, all among the 692 cases without documented treatment supporter.

CONCLUSIONS

The study has shown that pediatricians have started following parts of the national policy guidelines for management of childhood TB. The documented use of diagnostic tools is increased but record keeping of case management practices remained inadequate. This seems to increase case finding substantially but the treatment outcomes were poor mainly due to unknown outcomes. Development and implementation of standardized operational tools and regular monitoring system may improve the services.

Tuberculosis as part of the natural history of HIV infection in developing countries

An enhanced, refocused research agenda is critical to reducing the burden of tuberculosis (TB) in the human immunodeficiency virus (HIV) epidemic in developing countries. TB threatens HIV-infected patients before and after initiation of antiretroviral therapy, is difficult to diagnose, is rapidly fatal when it is drug resistant, and is being spread in clinics and hospitals. Research priorities include improved and point-of-care TB diagnostics; TB treatment and prevention during HIV infection, drug-resistant TB, and childhood TB; and optimization of TB and HIV program integration. With new TB diagnostics and drugs reaching approval, research must focus on effectively deploying these advancements. Research must include evaluations of individual, household, health care, and community approaches. Studies must apply implementation science to determine how to increase and adapt effective interventions to reduce TB burden in the context of HIV infection. Investment in this research will improve the lives of persons infected with HIV and contribute to efforts to reduce the global TB burden.