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The cost effectiveness of nucleic acid amplification techniques for the diagnosis of tuberculosis |
Hughes R, Wonderling D, Li B, Higgins B |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. CRD summary This study assessed the cost-effectiveness of the available strategies for the routine diagnosis of tuberculosis, including nucleic acid amplification techniques (NAAT), culture, and sputum smear microscopy. The authors concluded that the best testing strategy was microscopy plus culture, while strategies including NAAT were not likely to be cost-effective, unless the prevalence of tuberculosis was high. The methods were valid and transparent, which supports the authors’ conclusions. Type of economic evaluation Study objective This study assessed the cost-effectiveness of the available strategies for the routine diagnosis of tuberculosis, including nucleic acid amplification techniques (NAAT), culture, and sputum smear microscopy. Interventions The analysis considered eleven testing strategies. Three options were microscopy followed by culture if the smear was positive, if the smear was negative, or for all smears. Another three options were microscopy followed by NAAT if the smear was positive and culture if it was negative, or vice versa, or NAAT for all smears and culture if the two results disagreed. Four options were NAAT followed by culture if the result was positive, if it was negative, or for all results, and NAAT alone. The last option was microscopy, NAAT, and culture for all results. Methods Analytical approach:The analysis was based on a decision-tree model, with a one-year time horizon. The authors stated that it was carried out from the perspective of the UK NHS and Personal Social Services (PSS). Effectiveness data:Most of the clinical data were identified by systematic reviews of the literature, and most of the evidence was from one UK health technology assessment. Some inputs were based on expert opinion, such as the prevalence of tuberculosis. The treatment effectiveness was assumed to be 100%, based on the results of a Cochrane review. The accuracy of the testing strategies was a key input for the model. The accuracy of culture was assumed to be 100% as it was the gold standard in most of the published analyses. Monetary benefit and utility valuations:The utility values were identified by searching the Cost Effectiveness Analysis (CEA) Registry, and were from published sources. Measure of benefit:Quality-adjusted life-years (QALYs) were the summary benefit measure. Cost data:The economic analysis included the costs of the tests, drugs, out-patient visits, and the management of multidrug resistant tuberculosis. The patterns of resource consumption were from the World Health Organization (WHO) guidance and published UK studies. The drug costs were from generic UK list prices. Out-patient costs were based on official Department of Health tariffs. The cost of managing multidrug resistant tuberculosis was from the guidelines of the National Institute for Health and Clinical Excellence (NICE). All costs were in UK pounds sterling (£). Analysis of uncertainty:Deterministic sensitivity analyses were carried out on selected inputs, using published ranges of values. A probabilistic sensitivity analysis was carried out by assigning conventional distributions to the model inputs. Results The mean one-year costs were £233.65 for culture if microscopy positive, £260.51 for culture if microscopy negative, £258.85 for microscopy and culture, £364.41 for microscopy and NAAT with culture if different, £273.67 for NAAT if microscopy positive and culture if negative, £349.57 for NAAT if microscopy negative and culture if positive, £374.56 for NAAT and culture, £352.88 for NAAT alone, £350.66 for culture if NAAT positive, £376.79 for culture if NAAT negative, and £390.50 for microscopy, NAAT and culture. The QALYs were 0.842 for culture if microscopy positive, 0.844 for culture if microscopy negative, 0.844 for microscopy and culture, 0.845 for microscopy and NAAT with culture if different, 0.844 for NAAT if microscopy positive and culture if negative, 0.845 for NAAT if microscopy negative and culture if positive, 0.846 for NAAT and culture, 0.844 for NAAT alone, 0.844 for culture if NAAT positive, 0.846 for culture if NAAT negative, and 0.846 for microscopy, NAAT and culture. After excluding the dominated strategies, which were less effective and more expensive or less cost-effective than another strategy, the most cost-effective option at a threshold of £20,000 per QALY, was microscopy and culture, with an incremental cost per QALY gained of £9,748, over culture if microscopy positive. The next most cost-effective option was microscopy, NAAT and culture, with an incremental cost per QALY gained of £64,723. The results were sensitive to changes in the prevalence. NAAT if microscopy negative and culture if positive was cost-effective at very high prevalence (above 46%), microscopy and culture remained the preferred option for rates between 10% and 46% (20% in the base case), and culture if microscopy positive was preferred for rates below 10%. In general, microscopy and culture remained the preferred option in most scenarios, and was cost-effective at the threshold of £20,000 per QALY gained, in 90% of simulations. Authors' conclusions The authors concluded that the best testing strategy was microscopy plus culture, while strategies including NAAT were not likely to be cost-effective, unless the prevalence of tuberculosis was high. CRD commentary Interventions:The rationale for the selection of the comparators was clear as the authors included all the available testing strategies. Bacterial culture was appropriately considered as the gold standard with 100% accuracy. Effectiveness/benefits:The clinical data were mainly from systematic reviews of the literature, which should have identified the most relevant studies, but these were not described. Some key estimates, such as the disease prevalence, were experts’ opinions and were substantially tested in the sensitivity analyses. The authors stated that the assumption of 100% accuracy for culture might not be true, and this could have biased the results against NAAT, but the results were generally quite stable to changes in the clinical parameters. QALYs were an appropriate benefit measure; they not only capture the impact of the disease on the patients’ health, but also allows comparisons to be made with the benefits of other health care interventions. Other model outcomes, such as the number of infections, false positives, and false negatives, were reported. UK sources appear to have been used for the utility weights. Costs:The economic analysis was appropriately carried out. The cost categories were consistent with the perspective adopted and the key unit costs and resource quantities were clearly reported. Official NHS sources were used for the costs, and the patterns of resource consumption reflected the conventional management of tuberculosis. The price year was not reported, preventing reflation exercises. The costs were varied in the probabilistic sensitivity analysis. Analysis and results:The expected costs and benefits were clearly presented and were combined, using an appropriate incremental approach. The uncertainty was satisfactorily investigated, using valid approaches, and the methods and results were extensively presented. The authors acknowledged some limitations to their analysis, which mainly related to the need for assumptions and the use of a simplistic model. They also stated that the analysis did not incorporate secondary infections, which might have had an impact on the costs and health benefits. The transferability of the results was not discussed and they might be specific to the UK setting. Concluding remarks:The methods were valid and transparent, which supports the authors’ conclusions. Bibliographic details Hughes R, Wonderling D, Li B, Higgins B. The cost effectiveness of nucleic acid amplification techniques for the diagnosis of tuberculosis. Respiratory Medicine 2012; 106(2): 300-307 Indexing Status Subject indexing assigned by NLM MeSH Cost-Benefit Analysis; Decision Trees; Direct Service Costs; Female; Great Britain /epidemiology; Humans; Male; Microscopy /economics /methods; National Health Programs /economics; Nucleic Acid Amplification Techniques /economics /methods; Prevalence; Quality-Adjusted Life Years; Sensitivity and Specificity; Tuberculosis /diagnosis /economics /genetics AccessionNumber 22012001138 Date bibliographic record published 22/02/2012 Date abstract record published 07/03/2012 |
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