Decreased Time to Treatment Initiation for Multidrug-Resistant Tuberculosis Patients after Use of Xpert MTB/RIF Test, Latvia

Abstract

Few studies have examined whether the Xpert MTB/RIF test improves time to treatment initiation for persons with multidrug-resistant tuberculosis (MDR TB). We determined the impact of this test in Latvia, where it was introduced in 2010. After descriptive analyses of pulmonary MDR TB patients in Latvia during 2009-2012, time to treatment initiation was calculated, and univariate and multivariable accelerated failure time models were constructed. Univariate results showed strong evidence of an association between having rifampin-resistant TB detected by Xpert MTB/RIF and reduced time to treatment initiation versus the test not being used. A multivariable model stratifying by previous TB showed similar results. Our finding that in Latvia, time to treatment initiation was decreased for MDR TB cases that were rifampin-resistant TB by XpertMTB/RIF has implications for the use of this test in other settings with a high burden of MDR TB in which rifampin resistance is highly predictive of MDR TB.

Keywords: Latvia; MDR TB; Xpert MTB/RIF; antimicrobial resistance; bacteria; molecular diagnostics; multidrug resistance; multidrug-resistant tuberculosis; pulmonary; rifampin; time to treatment initiation; tuberculosis and other mycobacteria.

Figure 1

Diagnostic pathways for patients with multidrug-resistant tuberculosis, Latvia, 2012. A) With use of Xpert MTB/RIF; B) without use of Xpert MTB/RIF. A line probe assay was used if Xpert and DST showed discordant results. MTB, Mycobacterium tuberculosis; RIF, rifampin; TB, tuberculosis; DST, drug sensitivity testing; Xpert, Xpert MTB/RIF.

Figure 2

Conceptual framework of relationship between use of Xpert MTB/RIF and time to treatment initiation among patients with multidrug-resistant tuberculosis (MDR TB), Latvia, 2009–2012. Demographic and geographic variables were sex, age, country of birth, and region of Latvia. Clinical variables were previously having had tuberculosis, site of disease, and HIV status. Social risk factor variables were history of imprisonment, history of or current drug abuse, current homelessness, current dependence on alcohol. MTB, Mycobacterium tuberculosis; RIF, rifampin.

Figure 3

Relationship between use of Xpert MTB/RIF (Xpert) and time to treatment initiation among patients with multidrug-resistant tuberculosis (MDR TB) Latvia, 2009–2012. Shown are percentages of MDR-TB patients that underwent Xpert MTB/RIF testing (bars) and median time to treatment initiation (lines) with binomial distribution–derived CIs (error bars) for A) all patients and B) patients with and without testing by Xpert. MTB, Mycobacterium tuberculosis; RIF, rifampin.

Figure 4

Quantile–quantile plots of time to multidrug-resistant tuberculosis (MDR TB) treatment initiation by use and results of Xpert MTB/RIF (Xpert) for patients with MDR TB, Latvia, 2009–2012. Shown are time to MDR TB treatment initiation (days) for patients A) who were not tested by Xpert vs. those who had rifampin-resistant TB by Xpert, B) those who were not tested vs. those who had a negative result for rifampin-resistant TB, and C) those who were tested by Xpert and had positive vs. negative results for rifampin-resistant TB. MTB, Mycobacterium tuberculosis; RIF, rifampin.

Figure 5

Kaplan-Meier plot of time to treatment initiation by use and results of Xpert MTB/RIF in patients with multidrug-resistant tuberculosis (MDR TB), Latvia, 2009–2012. Shown is time to MDR TB treatment initiation (days) for patients who were not tested by Xpert MTB/RIF (dark gray line) and those who had rifampin-resistant TB by Xpert MTB/RIF (light gray line). MTB, Mycobacterium tuberculosis; RIF, rifampin.