Does Neutralization of Gastric Aspirates from Children with Suspected Intrathoracic Tuberculosis Affect Mycobacterial Yields on MGIT Culture?

Parashar, Deepak; Kabra, S. K.; Lodha, Rakesh; Singh, Varinder; Mukherjee, Aparna; Arya, Tina; Grewal, Harleen M. S.; Singh, Sarman

doi:10.1128/jcm.00202-13

Cited by 21 publications

(8 citation statements)

References 12 publications

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“…19 The wide difference in yield between smear and culture, in contrast to our study, was probably due to patients having early disease with minimal changes on 20 In our study, although the samples were not neutralised, the contamination rate was significantly higher in specimens with >5 ml volume, presumably because of the fluid instilled before aspiration.…”

Section: Discussioncontrasting

confidence: 83%

Gastric specimens for diagnosing tuberculosis in adults unable to expectorate in Rawalpindi, Pakistan

Aslam¹,

Tahseen²,

Schomotzer

et al. 2017

public health action

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Section: Discussioncontrasting

confidence: 83%

Gastric specimens for diagnosing tuberculosis in adults unable to expectorate in Rawalpindi, Pakistan

Aslam¹,

Tahseen²,

Schomotzer

et al. 2017

public health action

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“…Samples of 5 to 10 ml are collected on 3 consecutive days, and if not processed within 4 h of collection, they should be adjusted to neutral pH with sodium carbonate since long-term exposure to acid can be detrimental to mycobacteria (10). However, one recent study reported that culture yield of nonneutralized specimens was, in fact, superior to neutralized specimens (11). Additionally, many recent studies have demonstrated that sputum can be induced from children as young as 1 month of age and that the microbiologic yield from one wellcollected induced sputum (IS) is similar to that from 3 gastric aspirates (4).…”

Section: Specimen Selection Collection and Transportmentioning

confidence: 99%

Laboratory Diagnosis of Mycobacterium tuberculosis Infection and Disease in Children

2016

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Diagnosis of tuberculosis in children is challenging; even with advanced technologies, the diagnosis is often difficult to confirm microbiologically in part due to the paucibacillary nature of the disease. Clinical diagnosis lacks standardization, and traditional and molecular microbiologic methods lack sensitivity, particularly in children. Immunodiagnostic tests may improve sensitivity, but these tests cannot distinguish tuberculosis disease from latent infection and some lack specificity. While molecular tools like Xpert MTB/RIF have advanced our ability to detectMycobacterium tuberculosisand to determine antimicrobial resistance, decades old technologies remain the standard in most locales. Today, the battle against this ancient disease still poses one of the primary diagnostic challenges in pediatric laboratory medicine.

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“…We have earlier reported that GA samples provide better yields than IS samples [ 19 ]. In a subsequent report we also showed that neutralizing the pH of gastric aspirate before processing leads to a higher rate of contamination without improving the detection rate [ 20 ]. In the present study we report on the performance of the Xpert MTB/RIF on archived GA and IS samples collected on two consecutive days from children with probable intrathoracic TB, recruited as part of a double blinded randomized controlled trial to study the role of micronutrient supplementation in children with intra-thoracic tuberculosis.…”

Section: Introductionmentioning

confidence: 99%

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

Singh

Prajapati

et al. 2015

BMC Microbiol

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BackgroundTuberculosis (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.MethodsWe 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.ResultsSample 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.DiscussionConfirmatory 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 foundthat combination of multiple samples and multiple diagnostic tests can give much better yield, though notoptimum. 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 thesensitivity 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.ConclusionThis 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.

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Does Neutralization of Gastric Aspirates from Children with Suspected Intrathoracic Tuberculosis Affect Mycobacterial Yields on MGIT Culture?

Cited by 21 publications

References 12 publications

Gastric specimens for diagnosing tuberculosis in adults unable to expectorate in Rawalpindi, Pakistan

Gastric specimens for diagnosing tuberculosis in adults unable to expectorate in Rawalpindi, Pakistan

Laboratory Diagnosis of Mycobacterium tuberculosis Infection and Disease in Children

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

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