Tuberculosis Research and Treatment / 2017 / Article / Tab 2

Research Article

Using Reduced Inoculum Densities of Mycobacterium tuberculosis in MGIT Pyrazinamide Susceptibility Testing to Prevent False-Resistant Results and Improve Accuracy: A Multicenter Evaluation

Table 2

Compiled PZA results for 14 susceptible and 3 resistant isolates tested in duplicate by 9 laboratories.

OutcomePredicted totalNumber (%) by inoculation method

True-susceptible252186 (61.2)226 (76.4)230 (79.2)
True-resistant5452 (17.1)42 (14.2)42 (14.5)
False-resistant064 (21.1)17 (5.7)8 (2.8)
False-susceptible02 (0.7)11 (3.7)9 (3.1)

Total valid tests306304296289
Timed Out02 (0.7)10 (3.3)17 (5.6)

Total tests306306306306

Results from three isolates categorized as “inconclusive” not included. Results for one laboratory excluded due to <70% reproducibility. 18 of the false-susceptible results occurred in isolate 17. The remaining 4 occurred in isolate 14, all in the same laboratory. Denominators used to calculate outcome percentage. Test result not achieved within the 21-day instrument protocol. 19 of these events occurred in one strain (isolates 11 and 23). Denominator used to calculate Timed-Out percentages.

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