Equipment and supply costs are a barrier to scaling up Xpert in many countries.
Countries also need to factor in the cost of treatment for each MDR-TB case detected by Xpert. The cost of drugs for treating an MDR-TB case is 50 to 200 times greater than treating a drug-sensitive TB case, and the overall costs to care for each MDR-TB case are 10 times higher.9 Many countries do not currently have the financial resources to treat their existing MDR-TB patients, and the detection of additional cases by Xpert is likely to further strain such health systems.
Prioritizing According to Country Circumstances
When, where, and how to use Xpert depends on the national commitment to draft policies and implementation strategies; available funds; accessibility, availability, and geographic distribution of adequate diagnostic services; and the epidemiology of TB in the country (especially HIV-associated TB and MDR-TB). Positioning of Xpert machines in the country needs to balance available resources, national capacity building, and accessibility to persons suspected of having TB that would most benefit from the diagnostic test.
Because it is a new and expensive technology, many countries are placing their first machines in central- and regional-level labs to gain knowledge, build a cadre of staff who can provide technical assistance on the assay, and most importantly, test as many people suspected of having TB as possible. Given limited resources, Xpert should be targeted to at-risk populations, particularly those with suspected HIV-associated TB and/or MDR-TB, to produce a high yield and high impact of early diagnosis. In addition, many countries continue to do parallel diagnostic smear microscopy to preselect persons suspected of having TB and build the local evidence base, but also because their national policies to treat and monitor TB patients rely on smear microscopy status.
Testing and Treatment Algorithms
Xpert should be incorporated into a diagnostic and treatment algorithm that includes all diagnostic tests needed to place a patient on an adequate drug regimen. In some settings, such as among populations with a low frequency of MDR-TB or high frequency of RIF-resistant TB, this may include confirmation of RIF resistance or MDR-TB by conventional culture and DST.
Diagnosing and Treating MDR-TB
Many countries currently have limited ability to address drug-resistant TB. Lack of TB culture and DST facilities and referral systems continues to delay diagnosis and treatment. Drugs for MDR-TB are available, but they are expensive and often require injections and up to 2 years of treatment. Similarly, weak MDR-TB treatment capacity, including facilities and staff, means that confirmed drug-resistant cases may go untreated until these systems are strengthened. This poses a substantial dilemma for countries who must weigh the benefits of diagnosing MDR-TB against the ethics of not being able to provide sufficient treatment. Increased capacity to detect MDR-TB should dictate that countries and their partners significantly ramp up treatment capacity.