Cost-effectiveness of point-of-care creatinine testing to assess kidney function prior to contrast-enhanced computed tomography imaging.

BACKGROUND: Patients undergoing contrast-enhanced computed tomography (CECT) imaging in a non-emergency outpatient setting often lack a recent estimated Glomerular Filtration Rate measurement. This may lead to inefficiencies in the CECT pathway. The use of point-of-care (POC) creatinine tests to evaluate kidney function in these patients may provide a safe and cost-effective alternative to current practice, as these can provide results within the same CECT appointment. METHODS: A decision tree model was developed to characterise the diagnostic pathway and patient management (e.g., intravenous hydration) and link these to adverse renal events associated with intravenous contrast media. Twelve diagnostic strategies including three POC devices (i-STAT, ABL800 Flex and StatSensor), risk factor screening and laboratory testing were compared with current practice. The diagnostic accuracy of POC devices was derived from a systematic review and meta-analysis; relevant literature sources and databases informed other parameters. The cost-effective strategy from a health care perspective was identified based on highest net health benefit (NHB) which were expressed in quality-adjusted life years (QALYs) at £20,000/QALY. RESULTS: The cost-effective strategy, with a NHB of 9.98 QALYs and a probability of being cost-effective of 79.3%, was identified in our analysis to be a testing sequence involving screening all individuals for risk factors, POC testing (with i-STAT) on those screening positive, and performing a confirmatory laboratory test for individuals with a positive POC result. The incremental NHB of this strategy compared to current practice, confirmatory laboratory test, is 0.004 QALYs. Results were generally robust to scenario analysis. CONCLUSIONS: A testing sequence combining a risk factor questionnaire, POC test and confirmatory laboratory testing appears to be cost-effective compared to current practice. The cost-effectiveness of POC testing appears to be driven by reduced delays within the CECT pathway. The contribution of intravenous contrast media to acute kidney injury, and the benefits and harms of intravenous hydration remain uncertain.

Point-of-care creatinine tests to assess kidney function for outpatients requiring contrast-enhanced CT imaging: systematic reviews and economic evaluation.

BACKGROUND: Patients with low estimated glomerular filtration rates may be at higher risk of post-contrast acute kidney injury following contrast-enhanced computed tomography imaging. Point-of-care devices allow rapid measurement of estimated glomerular filtration rates for patients referred without a recent estimated glomerular filtration rate result. OBJECTIVES: To assess the clinical effectiveness and cost-effectiveness of point-of-care creatinine tests for outpatients without a recent estimated glomerular filtration rate measurement who need contrast-enhanced computed tomography imaging. METHODS: Three systematic reviews of test accuracy, implementation and clinical outcomes, and economic analyses were carried out. Bibliographic databases were searched from inception to November 2018. Studies comparing the accuracy of point-of-care creatinine tests with laboratory reference tests to assess kidney function in adults in a non-emergency setting and studies reporting implementation and clinical outcomes were included. Risk of bias of diagnostic accuracy studies was assessed using a modified version of the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool. Probabilities of individuals having their estimated glomerular filtration rates correctly classified were estimated within a Bayesian framework and pooled using a fixed-effects model. A de novo probabilistic decision tree cohort model was developed to characterise the decision problem from an NHS and a Personal Social Services perspective. A range of alternative point-of-care testing approaches were considered. Scenario analyses were conducted. RESULTS: Fifty-four studies were included in the clinical reviews. Twelve studies reported diagnostic accuracy for estimated glomerular filtration rates; half were rated as being at low risk of bias, but there were applicability concerns for most. i-STAT (Abbott Point of Care, Inc., Princeton, NJ, USA) and ABL (Radiometer Ltd, Crawley, UK) devices had higher probabilities of correctly classifying individuals in the same estimated glomerular filtration rate categories as the reference laboratory test than StatSensor® devices (Nova Biomedical, Runcorn, UK). There was limited evidence for epoc® (Siemens Healthineers AG, Erlangen, Germany) and Piccolo Xpress® (Abaxis, Inc., Union City, CA, USA) devices and no studies of DRI-CHEM NX 500 (Fujifilm Corporation, Tokyo, Japan). The review of implementation and clinical outcomes included six studies showing practice variation in the management decisions when a point-of-care device indicated an abnormal estimated glomerular filtration rate. The review of cost-effectiveness evidence identified no relevant studies. The de novo decision model that was developed included a total of 14 strategies. Owing to limited data, the model included only i-STAT, ABL800 FLEX and StatSensor. In the base-case analysis, the cost-effective strategy appeared to be a three-step testing sequence involving initially screening all individuals for risk factors, point-of-care testing for those individuals with at least one risk factor, and including a final confirmatory laboratory test for individuals with a point-of-care-positive test result. Within this testing approach, the specific point-of-care device with the highest net benefit was i-STAT, although differences in net benefit with StatSensor were very small. LIMITATIONS: There was insufficient evidence for patients with estimated glomerular filtration rates < 30 ml/minute/1.73 m2, and on the full potential health impact of delayed or rescheduled computed tomography scans or the use of alternative imaging modalities. CONCLUSIONS: A three-step testing sequence combining a risk factor questionnaire with a point-of-care test and confirmatory laboratory testing appears to be a cost-effective use of NHS resources compared with current practice. The risk of contrast causing acute kidney injury to patients with an estimated glomerular filtration rate of < 30 ml/minute/1.73 m2 is uncertain. Cost-effectiveness of point-of-care testing appears largely driven by the potential of point-of-care tests to minimise delays within the current computed tomography pathway. FUTURE WORK: Studies evaluating the impact of risk-stratifying questionnaires on workflow outcomes in computed tomography patients without recent estimated glomerular filtration rate results are needed. STUDY REGISTRATION: This study is registered as PROSPERO CRD42018115818. FUNDING: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 39. See the NIHR Journals Library website for further project information.

Before computed tomography scans are done, a contrast agent is usually needed to improve the visibility of internal body structures. After receiving a contrast agent (through a vein), some patients' kidneys may be affected, especially if their kidneys already do not work well. A blood test can identify these patients before a computed tomography scan, to reduce the risk of kidney harm. The blood test measures creatinine, which is a marker of how well the kidneys work. Before a contrast-enhanced computed tomography scan, some patients have a recent creatinine result from an earlier blood test. Blood tests are normally done in a central laboratory, and usually take at least 1 hour. Other patients do not have a recent creatinine result, so their computed tomography scan may be delayed or rearranged. Sometimes, to avoid risking kidney harm, patients may have scans without contrast. 'Point-of-care' (handheld, tabletop or portable) devices can quickly measure creatinine (usually in patients with risk factors), often from a finger-prick blood sample. Many point-of-care devices are available but they may not be as exact as laboratory tests, so their benefit is unclear. This study reviewed all available evidence on the benefits and harms of point-of-care creatinine tests before computed tomography scans and assessed whether or not they are a cost-effective use of NHS resources. The study found that some devices [i.e. i-STAT (Abbott Point of Care, Inc., Princeton, NJ, USA) and ABL (Radiometer Ltd, Crawley, UK)] were more accurate than others [i.e. StatSensor^® (Nova Biomedical, Runcorn, UK)]. There was insufficient evidence for other devices. The study found that, for outpatients, doing a point-of-care test in patients who are at a higher risk of kidney harm (according to a questionnaire) and then confirming this with a laboratory test appeared to be a cost-effective use of NHS resources. The study found that the risk of kidney harm as a result of contrast agents appears very low. The main benefit of point-of-care testing may be to reduce needless delays or rearranged computed tomography scan appointments.

The Acceptability of Iterative Reconstruction Algorithms in Head CT: An Assessment of Sinogram Affirmed Iterative Reconstruction (SAFIRE) vs. Filtered Back Projection (FBP) Using Phantoms.

BACKGROUND: Computed tomography (CT) is the primary imaging investigation for many neurologic conditions with a proportion of patients incurring cumulative doses. Iterative reconstruction (IR) allows dose optimization, but head CT presents unique image quality complexities and may lead to strong reader preferences. OBJECTIVES: This study evaluates the relationships between image quality metrics, image texture, and applied radiation dose within the context of IR head CT protocol optimization in the simulated patient setting. A secondary objective was to determine the influence of optimized protocols on diagnostic confidence using a custom phantom. METHODS AND SETTING: A three-phase phantom study was performed to characterize reconstruction methods at the local reference standard and a range of exposures. CT numbers and pixel noise were quantified supplemented by noise uniformity, noise power spectrum, contrast-to-noise ratio (CNR), high- and low-contrast resolution. Reviewers scored optimized protocol images based on established reporting criteria. RESULTS: Increasing strengths of IR resulted in lower pixel noise, lower noise variance, and increased CNR. At the reference standard, the image noise was reduced by 1.5 standard deviation and CNR increased by 2.0. Image quality was maintained at ≤24% relative dose reduction. With the exception of image sharpness, there were no significant differences between grading for IR and filtered back projection reconstructions. CONCLUSIONS: IR has the potential to influence pixel noise, CNR, and noise variance (image texture); however, systematically optimized IR protocols can maintain the image quality of filtered back projection. This work has guided local application and acceptance of lower dose head CT protocols.