Tuberculosis Research and Treatment / 2017 / Article / Tab 4

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 4

Comparison of predicted to actual MGIT PZA susceptibility test results stratified by inoculation method. Cumulative results of 9 laboratories each testing 20 isolates in duplicate.

Isolate
number
Predicted
result (category)
Actual number of results
by inoculation method
BDAC
SRSRSR

1S (A)180180180
4R (A)018018018
7S (A)171170161
8S (A)180180180
11S (A)180140120
12S (P)116135153
13S (P)126180170
14R (A)018215216
16S (P)99152180
17R (P)2169978
18S (A)144180180
19INC135180180
20S (A)171180180
21INC612135144
22S (A)180180180
23S (A)170160120
24S (P)315117153
25S (P)126180170
26S (P)126153171
27INC711144135

Results for one laboratory excluded due to <70% reproducibility. Isolate numbers correspond to those in Table 1. S: susceptible; R: resistant; INC: inconclusive; A: always; P: predominately. Total results by method less than 18 (9 laboratories × 2 tests per isolate) indicate that some tests “Timed-Out” prior to a result. All 4 false-susceptible results occurred in the same laboratory.

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