Cartridge-based nucleic acid amplification test (Xpert Mycobacterium tuberculosis/Rifampicin Assay): An essential molecular diagnostic test for early diagnosis and initiation of treatment in childhood tuberculous meningitis and primary multidrug-resistant cases

Abstract

Background: Tuberculosis (TB) still remains the major public health threat in India. Early diagnosis, so as to initiate early treatment is a priority as any delay, may complicate the prognosis further leading to the failure of an effective control. India accounts for 6% incidence of pediatric TB cases in a population that has 40% as estimated latent TB cases. Pediatric samples were considered as the key population in the study. TB remains the most common cause of childhood meningitis in high burden countries. India accounted for the highest number of TB deaths among children in the year 2015, followed by Nigeria and China. Of which, tuberculous meningitis (TBM) stands to be the most common cause of morbidity. Extrapulmonary TB accounts for 25% of the total TB cases reported among which the most severe form being TBM. Although severe and difficult to diagnose due to lack of specific tests to get confirmed, cartridge-based nucleic acid amplification test (CBNAAT) is the only solution for microbiological confirmation of the disease for early treatment initiation and reduction of morbidity and mortality. Previously, due to lower case detection rates owing to inadequate diagnostic facilities of higher analytical sensitivity, the mortality and morbidity continued to be in the higher range, and empirical treatment modality was the mainstay till the CBNAATs came into existence. The increase in the case detection for tuberculous meningitis at a manageable stage of the disease would help in decreasing the mortality rates. The study explores the increased case detection rates among pediatric population suffering from tuberculous meningitis from referral units to Intermediate Reference Laboratory (IRL), Kolkata. Cerebrospinal fluid (CSF) from the pediatric patients has not been very difficult procedure though invasive, especially in the pediatric age group, and can be practiced at peripheral unit having CBNAAT facility. Methods: CSF from pediatric patients showing obvious clinical signs of meningitis was collected from tertiary unit linked to IRL, Kolkata, and tested on CBNAAT by Xpert Mycobacterium tuberculosis/ rifampicin (RIF) (Cepheid) along with all the pulmonary and extrapulmonary samples based on the manufacturer's instruction. The data were captured in the Inbuilt software of the GeneXpert MTB/RIF (Xpert) and Genotype MTBDRplus (DRplus) (Cepheid , USA) of the cartridge based nucleic acid amplification test machines automatically during the tests and exported to the Microsoft Excel sheets for further analysis. A defined study design against each and every objective was setup to analyze the effective detection of tuberculous meningitis case and their resistance to RIF along with the other pulmonary and extrapulmonary samples. Results and Conclusions: The study concluded the confirmation of tuberculous meningitis cases by the help of CBNAAT. The detection of microbiologically confirmed TB by these specimens sent from the referral unit linked with IRL, Kolkata, for pulmonary and extrapulmonary cases along with tuberculous meningitis cases is significant and facilitates the early initiation of treatment for TB and more so to those who are newly detected as multidrug-resistant TB especially below the 6 months of age. About 5% prevalence and around 4.9% incidence are an alarming situation in the TB control scenario of West Bengal. The positive case detection among the CSF samples was found to be more in the 0.6–1-year group followed by the age group of 1–5 years. The percentage positivity of CSF is recorded as 2.38%, and the percentage of RIF resistance among positive cases from CSF was found to be 13.79% (n = 28).

Keywords

• cartridge-based nucleic acid amplification test
• cerebrospinal fluid
• childhood pulmonary tuberculosis