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Abbott Provides Update on Multi-Drug Resistant TB Test for Centralized Labs

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NEW YORK (GenomeWeb) – Abbott Diagnostics has recently completed a study in South Africa of its CE-marked multi-drug resistant tuberculosis test, the first on the market to identify resistance to both rifampin and isoniazid.

The study found that the assay, which runs on the firm's automated m2000 RealTime System qPCR platform, is at least as sensitive as current commercial molecular tests designed for decentralized testing, such as Cepheid's GeneXpert MTB/RIF.

In addition, a representative from Abbott told GenomeWeb this week that even though the m2000 system is designed primarily for use in centralized laboratories, it may still provide some advantages for TB testing in resource-poor areas of the world.

Decentralized testing is currently the preferred approach to combating tuberculosis, and platforms that accomplish point-of-care diagnosis are heavily subsidized.

Although developing countries with a high burden of TB infections often have fewer centralized labs and fewer well-trained people to run them compared to developed countries, centralized lab testing has some advantages in these regions.

Firstly, no decentralized platform is yet capable of running assays for both rifampin and isoniazid resistance. Cepheid's GeneXpert MTB/RIF, the most widely deployed test in areas with high disease burden, tests only for rifampin resistance genes.

Cepheid has described development of a new assay for extensive drug resistance, called Xpert XDR-TB, which will detect resistance to other drugs, including isoniazid, rifampin, aminoglycosides, and fluoroquinolones. But that test may not be ready for launch until 2017.

Secondly, although expert technicians may be scarce in developing countries, they are likely to be more adept at running diagnostics tests and provide more reliable results.

With the new Abbott assay, centralized testing can thus "provide the ability to identify both resistant strains and improved sensitivity," Robert Bilkovski, senior associate medical director of molecular diagnostics at Abbott, told GenomeWeb in an email.

Citing the World Health Organization Global TB report of 2014, Bilkovski noted that isoniazid resistance is now the most common type of TB infection resistance worldwide.

Abbott recently presented a head-to-head trial of its test at the International Aids Society conference in July. In a poster, the firm showed preliminary data from a trial in South Africa aimed at detecting so-called paucibaccilary TB, which is defined as a bacterial burden below 130 colony-forming units per ml.

In the trial, 302 patients with suspected TB were enrolled after visiting Hillbrow Community Health Center in Johannesburg, South Africa. They provided sputum samples that were tested in parallel using Xpert MTB/RIF and the Abbott MTB test.

The Abbott test was performed on the firm's m2000 real-time PCR instrument, with sample prep preformed on the mSample preparation system. The high-throughput testing was automated, required little hands-on time, and could test 94 samples per run with a turn-around time of 8 hours.

Positive specimens were reflexed to the automated Abbott RIF/INH resistance assay, which provides drug resistance profiles in an additional three hours using the same platform.

The poster noted that the Abbott test was able to detect six additional infections from raw sputum, and that overall sensitivity was statistically similar to the Xpert test.

Furthermore, the test was designed to reduce the risk to technicians of handling infectious specimens by employing a bacterial inactivation step. And co-infection with HIV, which is a massive problem in some TB-endemic areas, could be determined by running additional assays on the same instrument.

"This could also cut capital costs and technician training time," Bob Kunkler, senior director of global strategic marketing for molecular at Abbott also noted.

He noted that the assay is part of a much broader menu of infectious disease assays, which would also be available to any lab with the m2000 instrument.

Cepheid's qualitative HIV assay was recently CE marked, and a representative from that firm noted previously that systems purchased through the high-burden developing country program for TB testing can now run both HIV and TB assays.

The need and the market

A recent survey of all labs in the city of Kampala, Uganda published in PLoS One in July noted that city has 954 public, private, and academic laboratories running a total of 100 different diagnostics tests. These labs serve a city of 1.7 million people, and run an estimated 3.3 million tests annually.

The researchers assessed the cost and availability of all diagnostics tests —which included a few PCR-based diagnostics — and also assigned a quality score to each lab based on certain criteria.

The smaller laboratories in Kampala, which ran primarily point-of-care tests, tended to be the labs with the lowest quality scores, the study noted, adding, "The benefits of the POC format must be balanced against the challenge of assuring quality in the laboratories that will likely be using the tests."

In Kampala, the study found a notable gap in availability of TB testing. This is important, because TB is a member of the triumvirate of high-burden infectious diseases — along with HIV and malaria — responsible for around 30 percent of deaths in this region in a 2010 assessment.

High-volume laboratories account for only 2 percent of laboratories in Kampala, but perform 45 percent of overall testing volume, Lee Schroeder, a clinical pathologist at the University if Michigan and corresponding author on the Kampala study told GenomeWeb in an email.

Thus, "offering [a TB test] in high-volume, central laboratories will offer significant availability," he suggested.

Still, he pointed out that the widely most available tests in Kampala are ones that can be offered in both high complexity labs and at the point-of-care or in physician offices, and it is likely that low prices of $4 or less play a role in this highly availability.

Another recent study, published in a supplementary issue on tuberculosis by the Journal of Infectious Diseases, attempted to use input from the stakeholder community to describe an ideal test, providing a "target product profile" for a TB molecular diagnostic.

Notably, the cost of the ideal test was left undetermined by this analysis.

A higher price than that of the available technologies — Xpert MTB/RIF and Hain Genotype MTBDRplus are currently available under preferential pricing for approximately $10 per test, the study said — would be justified only if the new tests bring substantial added value in terms of improved performance, greater suitability for decentralization, and the number of drugs for which resistance can be detected.

With respect to pricing, Abbott's Kunkler said that the firm has been "providing cost-effective solutions for scale up of HIV viral load testing for years, including specialized services to support the development of testing capabilities and partnerships with NGOs, ministries of health, and funder countries on a global basis."

Furthermore, in June the firm was selected by the Global Fund as a panel supplier to offer one low access price for HIV scale-up testing and services to low- and middle-income countries receiving funding from that agency.

Abbott also committed to extend this price to other important infectious disease tests available on the m2000 system, including the TB assay, as well as hepatitis B and C viruses, human papillomavirus, and chlamydia and gonorrhea, Kunkler said.

Offering a consolidated testing solution could save users on capital costs, reduce technician training time, help minimize procurement of stock items, and allow scale-up for future testing needs of other diseases, he noted.

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