29.05.2024 | Correspondence
Diagnostic Accuracy of Cartridge Based Nucleic Acid Amplification Test (CBNAAT) in Stool Samples in Pediatric Tuberculosis: Authors' Reply
verfasst von:
Richa Singhal, Rajeshwar Dayal, Shailendra Bhatnagar, Madhu Nayak, Neeraj Yadav, Pankaj Kumar, Santosh Kumar, Hari Singh, Geetu Singh
Erschienen in:
Indian Journal of Pediatrics
|
Ausgabe 10/2024
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Excerpt
To the Editor: We are very thankful to Singhal T for comments on our paper entitled “Diagnostic accuracy of cartridge based nucleic acid amplification test (CBNAAT) in stool samples in pediatric tuberculosis” published in IJP [
1,
2]. Our response is as follows:
1.
Of 100 patients enrolled, 76 were classified as having TB as per the NTEP guidelines [
3]. Thirty-two patients had pulmonary TB and 44 patients had extrapulmonary TB. Of 44 EPTB cases, 5 cases had abdominal TB, 19 cases were classified as TB meningitis, 6 patients had features of TB meningitis with pneumothorax and/ pleural effusion. Seven patients had generalized lymphadenopathy. Four patients had bilateral pleural effusion with cervical lymphadenopathy with hepatosplenomegaly with inflammatory granulomas in liver and spleen. Two patients had splenic granulomas with loculated ascites with pleural effusion/pneumothorax. One patient had generalized lymphadenopathy with Pott’s spine. Many of the index patients with EPTB had vague respiratory symptoms.
2.
Out of 21 smear positive samples in GA, 14 cases had pulmonary TB and 7 had extrapulmonary TB. As mentioned in discussion part of the article, the smear positivity rate of the present study is comparable to studies done by Leonor et al. and Ganiem et al. where smear positivity was 23.04% and 19.3% respectively [
4,
5]. Out of the positive 57 gastric aspirate samples, 29 were positive in pulmonary TB cases and 28 were positive in EPTB cases. Out of the corresponding 56 positive stool samples, 28 were positive in pulmonary TB cases and 28 were positive in EPTB cases. The positive gastric aspirate and stool samples in EPTB cases in the present study may be due to presence of pulmonary involvement in these cases which was not picked up on chest X-ray (CXR). Studies have shown that CXR is a specific but not a very sensitive tool for diagnosis of pulmonary TB. There is high inter- and intra- observer variability. A normal chest radiograph does not rule out tuberculosis [
6‐
10].
3.
The present study reports comparable results of gastric aspirate and stool Xpert. As mentioned in the manuscript, there are multiple studies which have shown comparable results between the 2 samples [
11,
12].
4.
Simple One Step (SOS) method for processing of stool was used for CBNAAT testing in the present study as recommended by the WHO [
13,
14]. The stool specimen (3–5 g) was collected in falcon tubes. Stool sample containers were sent immediately to the Intermediate Reference Laboratory at the State TB and Demonstration Centre, situated in authors’ medical college campus, where they were stored in the refrigerator at 2–8 °C until testing was performed. Before testing, the stool samples were allowed to warm up to room temperature. Approximately 0.8 g or a thumbnail size (1 × 1.5 cm) amount of stool was directly transferred from the stool container into the sample reagent (SR) bottle using a wooden stick or applicator. The mixture was shaken vigorously for 30 s and then incubated for 10 min at room temperature. This step was repeated once. Debris free supernatant sample of 2 ml was transferred to the CBNAAT cartridge. All samples, SR bottles and cartridges were carefully labeled with a unique patient identifier (ID). The cartridges were loaded into the GeneXpert instrument and results obtained.
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