Evaluation of Induced Sputum against Gastric Juice Aspirate in the Diagnosis of Tuberculosis in Children: A Cross-sectional Study

Abstract

Introduction: Diagnosing Tuberculosis (TB) in children is difficult as they do not expectorate sputum on their own, and the sample is usually paucibacillary. Hence, alternative sampling methods like Gastric juice Aspiration (GA), which is the widely accepted method, and Induced Sputum (IS) collection, a more novel approach, are used. The IS method has several advantages, such as being less invasive, not requiring inpatient admission, causing less discomfort, and not necessitating overnight fasting, compared to the GA method. Aim: To evaluate IS against GA for diagnosing TB using XpertMTB/RIF assay, as well as mycobacterial culture, in children aged between 2 and 15 years. Materials and Methods: This cross-sectional study was conducted in the Department of Paediatrics at Christian Medical College and Hospital, Vellore, Tamil Nadu, India from June 2019 to March 2020, involving 138 children aged between 2 and 15 years who were being evaluated for TB. GA samples were collected after an overnight fast, and on the same day, atleast two hours later, IS samples were collected by trained staff. Both samples underwent mycobacterial smear and culture using the Mycobacteria Growth Indicator Tube (MGIT) method and Xpert MTB/RIF assay. Confirmation of pulmonary TB was based on atleast one of these tests being positive. The ‘Wong-Baker’ Visual Analogue Scale (VAS) was individually administered to each patient to compare the discomfort associated with GA and IS procedures. The differences in yield between IS and GA were tested for significance using the Two-sample test of proportions with a significance level set at 5%. McNemar's χ2 test was employed to compare matched observations. The Mann-Whitney test was used for comparing continuous variables, and the Chi-Square test for categorical variables. Cohen’s Kappa (κ) was used to assess interobserver agreement between the sampling methods using the different tests. Results: Out of the 138 cases recruited with suspected pulmonary TB, the diagnosis was microbiologically confirmed in 13 cases (9.4%). The overall diagnostic yield was 12/138 (8.7%) for GA and 10/138 (7.2%) for IS. In children under 10 years, GA outperformed IS with all three cases being positive by GA and none by IS. For those aged 10 years and above, 10 children (100%) tested positive with IS, while nine children (90%) were positive with GA. According to the Wong-Baker VAS measuring discomfort during the procedure, IS was favoured over GA (p-value<0.0001). Conclusion: IS performs similarly or better than GA in children over 10 years, while GA performs better than IS in children under 10 years of age. IS is reported to cause less discomfort than GA on the Wong-Baker VAS.

Keywords

• childhood tuberculosis
• diagnostic sampling
• gastric lavage
• paediatrics