Stool processing methods for Xpert Ultra testing in childhood tuberculosis: A prospective, multi-country accuracy...

Area of Science:

• Microbiology
• Infectious Diseases
• Pediatrics

Background:

• Centrifuge-free methods for stool Xpert Ultra testing in childhood tuberculosis (TB) are emerging.
• Limited data exist on the accuracy, acceptability, and usability of these novel TB diagnostic approaches.

Purpose of the Study:

• To prospectively evaluate the accuracy, acceptability, and usability of three centrifuge-free stool processing methods for Xpert Ultra testing in children with presumptive TB.
• To compare the performance of Stool Processing Kit (SPK), Simple One-Step (SOS), and Optimized Sucrose Flotation (OSF) against reference standards.

Main Methods:

• A prospective study involving 607 children (<15 years) with presumptive TB across India, South Africa, and Uganda.
• Stool samples were processed using SPK, SOS, and OSF, followed by Xpert Ultra testing.
• Accuracy was assessed against a microbiological reference standard (MRS) and a composite reference standard (CRS); laboratory staff usability and acceptability were surveyed.

Main Results:

• Sensitivities for SPK, SOS, and OSF against MRS were 36.9%, 38.6%, and 31.3%, respectively; specificities were high (97.1-98.2%).
• Laboratory staff found the methods acceptable and usable, with SOS noted as most feasible for peripheral settings.
• Sensitivity improved significantly in culture-positive children (55-77.3%) but remained low against the CRS (13-16.7%).

Conclusions:

• Centrifuge-free stool processing methods (SPK, SOS, OSF) for Xpert Ultra are acceptable and usable for childhood TB diagnosis.
• The methods demonstrated similar performance, with notable improvements in sensitivity for culture-positive TB cases.
• Further research may be needed to optimize sensitivity, particularly against composite reference standards.