The simple one-step stool processing method to diagnose tuberculosis is robust enough for global scale up
P de Haas(1) B Yenew(2) A Slyzkyi(1) K Kremer(1) E Klinkenberg(3) E Tiemersma(1)
1:KNCV Tuberculosis Foundation; 2:Ethiopian Public Health Institute; 3:Independent consultant, Connect TB
The diagnosis of pulmonary tuberculosis (TB) in children and people living with HIV is hampered because of nonspecific symptoms and lack of laboratory confirmation due to paucibacillary load and difficulty to obtain sputum. Use of stool as an alternative non-invasive sample is recommended by the World Health Organization as an initial diagnostic test for the detection of TB and rifampicin resistance in children with signs and symptoms of pulmonary TB.
The simple one step stool processing (SOS) method and Xpert-Ultra testing were used to detect Mycobacterium tuberculosis and rifampicin resistance. This method uses the same supplies and equipment as used for sputum testing. Several countries have introduced this method at program level. We have investigated the robustness of the SOS method by varying the quantity of stool, storage temperature, sedimentation time, shaking method and transport conditions.
In total 2,963 Xpert-Ultra results from 132 stool specimens of 47 TB patients were obtained. We compared Xpert-Ultra processing errors and MTB-positivity rates between the standard and modified stool processing procedures. Minor deviations from the standard SOS method did not significantly impact the Xpert-Ultra test results.
We confirmed the robustness of the SOS stool processing method and Xpert-Ultra testing for the detection of TB. The results showed that a wider range of stool quantity (0.3-0.8g) than we advised previously (0.8g) can be used without compromising Xpert test results. The SOS method provides a simple and cost-effective work-up close to point of care that is sufficiently robust for global scale-up.