(i) Assays with improved T cell phenotyping, like TAM-TB assay which has a sensitivity of 83.3% and specificity 96.8% but is not field ready as yet.
(ii)Using a selection of markers as a point of care screening test, by identifying a serological finger print of active TB--promising combinations have been identified but require validation.
(iii) Microscopically observed drug susceptibility (MODS) assay that has been successfully used in Peru and Hanoi and shown to be as sensitive as the GeneXpert. It is cheap with a quick turnaround time, but requires a BSL 2 laboratory facility, and is operator dependent.
(iv) PCR based Xpert MTB/RIF has been shown to be good also for extra thoracic samples like FNAB, bone marrow, and other tissue fluid. The new Xpert Ultra has a further improved sensitivity.
(v) The String test-- a noninvasive test for collecting sputum sample by swallowing a tablet with a thin string which is taped inside the patient's cheek--after 4 hours the string is withdrawn obtaining the sample. It is used in adults who cannot produce sputum. But the yield in children is lower and kids.
(vi) Stool samples by GeneXpert are being used to diagnose TB in children living with HIV
Creating child-friendly drug formulations and speeding the development of new childhood TB treatments is another issue that needs serious attention. In 2010 WHO had released revised dosing guidelines for paediatric TB drug doses (increasing the dosage per kg body weight for isoniazid, rifampicin and pyrazinamide), based on evidence that children were not receiving enough TB medicines. The guidance and policy changed, but treatments conforming to these guidelines were not produced. To this day, providers concoct their own formulations by splitting or crushing pills that are made for adults, leading to improper treatment, and resulting in poor health outcomes and development of drug resistance.
Lamenting that even today there is a lack of appropriately dosed quality assured easy to administer drugs for children with TB, Dr Cherise Scott of TB Alliance told CNS, "TB Alliance has been working with other partners for making paediatric formulations of the current first line TB drugs. It has developed child-friendly products, in the correct dosages, that are better tasting and simpler to administer. We hope these will be available in the market by 2016".
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