Applied Visual Sciences, Inc. (APVS.OB)
Today PLoS One (the Public Library of Science) releases the results of a TBDx™ study that models the cost effectiveness of combining TBDx™ with molecular diagnostic technologies, such as GeneXpert. Entitled Cost Effectiveness of Automated Digital Microscopy for Diagnosis of Active Tuberculosis (1), the study has been authored by renowned experts in the field of tuberculosis and diagnostic technologies.
Study Phase One
This is the second study of a two-phased research effort. The first study, published by the American Journal of Respiratory and Clinical Care Management, presented the evaluation of the TBDx™ automated microscopy system in algorithms for the diagnosis of TB.
This first phase concluded: “The TBDx™ system demonstrated potential as a useful triage tool, with GXP used to confirm intermediate results. This novel system could also potentially serve as a triage test for other emerging technologies, ensuring that these tools are efficiently used while maintaining good performance. As a stand-alone microscopy system, its performance was equivalent to that of a highly experienced TB microscopist, and its use has the potential to improve upon the existing diagnostic standard of care.”
Study Phase Two
The purpose of this second phase has been to assess the cost effectiveness of TBDx™ as a triage technology, in highly burdened countries, particularly where molecular tests are too expensive for routine use. The study evaluated the costs and effectiveness of four approaches:
- sputum smear microscopy alone;
- TBDx™ alone;
- TBDx™ with confirmation of low positive results using molecular testing; and,
- TBDx™ with confirmation of ALL positive results using molecular testing.
Performance data were drawn from the first phase, and unit costs were obtained from existing scientific literature for sputum microscopy, GeneXpert, and TBDx™. Overhead, utilities, quality assurance, training, shipping, import duties, maintenance, personnel, capital hardware and software licenses, and treatment costs were included in the overall evaluation.
Summary Findings Provided in the Report:
In both moderate (30 test / day) and high (100+ tests / day) volume laboratory settings the per-test cost of TBDx™ is approximately 33% of the cost of GeneXpert (Xpert MTB/RIF) (or 67% less than Xpert)
If TBDx™ is used as a triage technology, where Xpert confirms ONLY low positive cases, and all heavily burdened cases are automatically placed on treatment, 79% – 84% of Xpert positive cases could be diagnosed at 50%-60% of the cost of Xpert. This strategy has a favorable cost-effectiveness ratio of $1,280 per TB diagnosis, relative to manual smear microscopy performing at a 68% sensitivity rate. If manual sputum smears performance drops to 50% sensitivity (the performance of an average microscopist) the TBDx™ usage would lower the costs to $677 per TB diagnosis.
Use of TBDx™ as a triage tool would be a preferred strategy where resources are insufficient for universal Xpert testing, or where the “willingness to pay” falls within a cost ranging from $1,280 ($677 if smear microscopy performance averages 50%) and $1, 927.
Under most sensitivity analysis, the algorithm providing the most TB diagnosis per dollar spent was a TBDx™ triage test, followed by Xpert confirmation of low positive results, counting “Scanty 1” cases as negative.
Triage tests are intended to reduce costs, and provide a more favorable cost effectiveness ratio such that it is preferable to perform the triage test on the full population rather than the confirmatory test on part of it. This economic evaluation demonstrates precisely this result, specifically that automated digital microscopy can reduce the overall costs of diagnostic testing substantially, and be performed at a cost-effectiveness ratio that is generally favorable to that of universal Xpert. As the data show, TBDx™ is particularly attractive in settings where manual microscopy cannot be performed with consistent quality.
By reducing the costs of Xpert MTB / RIF testing while still providing the majority of the benefits (in terms of TB diagnosis) automated digital microscopy has the potential to fill an important niche in the TB diagnostic landscape.
(1) The study authors represent industry-leading universities and institutions who have played leadership roles in the evaluation and analysis of TB diagnostic technologies,. These include the Department of Epidemiology, The Johns Hopkins Bloomberg School of Public Health; The Center for Tuberculosis National Institute for Communicable Diseases in Johannesburg, South Africa; the Department of Microbiology at the University of Pretoria, Pretoria, South Africa; Aurum Institute in Johannesburg, South Africa; MRC Tropical Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK; and, School of Public Health, University of the Witswatersrand, Johannesburg, South Africa.