Comparison of time to positive and colony counting in an early bactericidal activity study of anti-tuberculosis treatment

Abstract

TTP measured by an automated, standardized, commercially available culture system correlates with cfu determinations. EBA measured by TTP provides similar information to cfu counting, and is reproducible across sites and in different patient populations. These findings support replacing cfu counting with TTP as the primary measurement in EBA studies.

Xpert MTB/RIF Testing in a Low Tuberculosis Incidence, High-Resource Setting: Limitations in Accuracy and Clinical Impact

“…This is suggested by the substantial number of asymptomatic subjects in our study. Furthermore, the time to positivity of mycobacterial cultures in our participants was longer than the expected average for liquid cultures, suggesting a low bacillary load-notably in those with negative Xpert results [21].…”

Differences in EBA in the first two days of standard anti-tuberculosis treatment in different geographic regions

“…1 The mean EBA 0-2, measured in colony forming units (CFU), from 40 patients receiving directly observed therapy (DOT) was 0.26 ± 0.24 log 10 CFU/ml/day. This result was similar to an EBA 0-2 value of 0.28 ± 0.42 log 10 CFU/ml/day we calculated using data from an earlier 2003 clinical trial conducted at the same site.…”

Robust Bayesian nonlinear mixed‐effects modeling of time to positivity in tuberculosis trials

“…If no positive mycobacteria growth indicator tube culture is reported after a specified maximum number of hours, the sputum sample status is reported as "no mycobacterial growth". 7 The TTP endpoint is considered more sensitive than CFU count in the evaluation of TB treatments. 8 Moreover, the collection of CFU counts is prone to contamination and involves a time-consuming and expensive counting process.…”

“…Time to positivity is the time it takes for a given sputum sample to yield a positive mycobacteria growth indicator tube culture. If no positive mycobacteria growth indicator tube culture is reported after a specified maximum number of hours, the sputum sample status is reported as “no mycobacterial growth” . The TTP endpoint is considered more sensitive than CFU count in the evaluation of TB treatments .…”