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Biomedical subjects

A R van Erkel

Publications and source records attributed to A R van Erkel.

13 recordsLinked to original sources
PubMed2001

Antibiotic prescription for acute sinusitis in otherwise healthy adults. Clinical cure in relation to costs.

OBJECTIVE: To determine which treatment strategy offers the most cost-effective option in managing acute sinusitis. DESIGN: The modelling procedure included five clinical strategies, varying from "wait and see for a week", to "prescribing antibiotics selectively" to "prescribing antibiotics immediately" and to "performing further diagnostics". SETTING: Outpatient clinics and primary health care. PATIENTS: Data were derived from clinical trials that included otherwise healthy patients with acute sinusitis. MAIN OUTCOME MEASURES: The marginal cost-effectiveness. RESULTS: By using the strategy "wait and see for a week", 91.5% of the patients, by "prescribing antibiotics selectively", 93.2%, of the patients, and by "prescribing antibiotics immediately", 94.5% of the patients were cured after a 1-week period. The costs for curing one additional patient were Dutch Florin (DFL) 516 when antibiotics were selectively prescribed, and DFL 882 when antibiotics were immediately prescribed. Further diagnostic procedures did not improve outcome in terms of marginal cost-effectiveness. CONCLUSIONS: In patients presenting with acute sinusitis, postponing antibiotics for 1 week is the most cost-effective strategy.

Acute Disease↗
PubMed1999

International differences in health care costs in Europe and the United States: Do these affect the cost-effectiveness of diagnostic strategies for pulmonary embolism?

The aim of this study was to assess whether potential differences in costs for diagnostic procedures and treatment of pulmonary embolism (PE) among European and U. S. hospitals alter the optimal cost-effective diagnostic strategy for PE. A standardized questionnaire was used to obtain cost data for the diagnosis and treatment of PE in participating European and U. S. hospitals. Costs for diagnostic tests and treatment of PE were then calculated in a standardized manner for all participating hospitals, from the hospital perspective. Costs were used in an existing cost-effectiveness analysis (CEA) model to determine the most cost-effective diagnostic strategy in participating hospitals. There were considerable differences in costs for diagnostic and therapeutic procedures for PE among the participating centers. These differences, however, did not affect the most cost-effective strategy based on incremental cost-effectiveness. In all hospitals the most cost-effective strategy appeared to be ultrasound followed by helical CT. International differences in cost of diagnostic and therapeutic procedures certainly exist and should be considered before applying a published CEA. Nevertheless, despite these cost differences, the diagnostic strategy for PE of ultrasound followed by helical CT appears most cost-effective.

Angiography↗
PubMed1998

Accuracy of helical CT for acute pulmonary embolism: ROC analysis of observer performance related to clinical experience.

The aim of this study was to test the influence of observer experience on the accuracy for interpreting helical CT for acute pulmonary embolism (PE) and to identify sources of observer errors. Three observers of different expertise blindly assessed 147 helical CT scans for suspected PE (true status regarding absence or presence of PE known from independent reference studies). These observers were (a) an experienced CT radiologist, (b) a fellow in CT, and (c) a second-year resident without any formal training in CT. None of them had prior experience with CT for PE. Firstly, 70 CT scans were scored without revealing true PE status. Afterwards, feedback was provided and another 77 CT scans were evaluated. The CT scans were scored on a 5-point confidence scale and receiver-operator-characteristic analysis was performed. Different sources of interpretation errors were analyzed. The two observers with CT experience were significantly more accurate than the unexperienced observer. Their performance was not influenced by feedback training. Certain observer errors were identified, but there was no clear difference among the three observers considering the type of errors. There is significant influence of observer experience on accuracy of reading helical CT for PE: A basic working experience with whole-body CT seems to be a prerequisite. These results suggest that with this experience any radiologist should be able to achieve good accuracy; helical CT thus might become a suitable technique for acute PE in routine clinical practice.

Acute Disease↗
PubMed1998

Receiver operating characteristic (ROC) analysis: basic principles and applications in radiology.

Receiver operating characteristic (ROC) analysis is a widely accepted method for analyzing and comparing the diagnostic accuracy of radiological tests. In this paper we will explain the basic principles underlying ROC analysis and provide practical information on the use and interpretation of ROC curves. The major applications of ROC analysis will be discussed and their limitations will be addressed.

Humans↗
PubMed1997

Hemodynamic significance of renal artery stenosis: digital subtraction angiography versus systolically gated three-dimensional phase-contrast MR angiography.

PURPOSE: To compare digital subtraction angiography with three-dimensional phase-contrast magnetic resonance (MR) angiography in detection of significant renal artery stenosis. MATERIALS AND METHODS: Sixteen patients underwent digital subtraction angiography and systolically gated three-dimensional phase-contrast MR angiography within 1 week. Scoring of stenosis on MR angiograms was based on presence and length of a flow void and quality of flow signal intensity in the distal part of the artery. Intraarterial pressure measurement was the reference standard for hemodynamically significant renal artery stenosis. RESULTS: MR angiography depicted two of five patent accessory arteries. Comparison of digital subtraction angiography and MR angiography with intraarterial pressure measurements was possible in 25 main renal arteries. In 13 arteries, a pressure gradient of more than 15 mm Hg was found. Digital subtraction angiography depicted 10 of these stenoses (sensitivity, 77%; specificity, 92%). A flow void was present at MR angiography in eight stenoses (sensitivity, 62%; specificity, 83%). In 12 of the stenosed vessels, distal flow signal intensity was impaired at MR angiography (sensitivity, 92%; specificity, 75%). There was no difference between the two modalities (P > .05) in grading hemodynamic significance of renal artery stenosis. CONCLUSION: Systolically gated MR angiography and digital subtraction angiography are equally effective in depicting hemodynamically significant stenoses in the main renal arteries. MR angiography, however, is not adequate in depiction of accessory renal arteries.

Adult↗
PubMed1996

Renal artery stenosis: endovascular flow wire study for validation of Doppler US.

PURPOSE: To compare the accuracy of proximal and peripheral Doppler parameters for detection of renal artery stenosis (RAS). MATERIALS AND METHODS: The authors obtained absolute velocities and peripheral Doppler waveforms in 16 stenotic and 14 normal renal arteries by using a 0.45-mm endovascular flow wire. Hemodynamically significant stenosis was established by measuring transstenotic invasive pressure gradients, with a 10 mm Hg or greater pressure drop indicating RAS. Accuracy of the Doppler parameters and of digital subtraction angiographic (DSA) results were compared by using receiver operating characteristic analysis. RESULTS: Measurements of absolute velocities at the site of the stenosis (maximal peak systolic velocity [PSVmax], PSV ratio, renal artery-to-aortic PVS ratio) showed high accuracy for diagnosis of RAS similar to that of DSA (areas under the ROC curve were 0.96, 0.97, 0.93, respectively). The distal intrarenal Doppler indexes (notably loss of early systolic peak, acceleration, acceleration time, pulsatility index, and resistive index) did not show statistically significant correlation with RAS. CONCLUSION: Doppler measurements in the main renal artery correlate well with RAS. The intrarenal Doppler spectrum, however, has no diagnostic value. The authors conclude that duplex Doppler US is not a suitable screening test for RAS.

Angiography, Digital Subtraction↗
PubMed1996

Spiral CT angiography for suspected pulmonary embolism: a cost-effectiveness analysis.

PURPOSE: To investigate the cost-effectiveness of diagnostic strategies involving spiral computed tomographic (CT) or conventional pulmonary angiography in the diagnosis of suspected pulmonary embolism. MATERIALS AND METHODS: A model was created for analyzing cost-effectiveness on the basis of available literature data. Diagnostic algorithms consisting of combinations of perfusion and ventilation scintigraphy, ultrasound, D-dimer assay, conventional angiography, and spiral CT angiography were compared. Preference for strategies was determined on the basis of the mortality and cost per life saved. RESULTS: For all realistic values of the pretest probability of pulmonary embolism and coexisting deep vein thrombosis and of the specificity of spiral CT angiography, all of the best strategies included spiral CT angiography. With an assumed sensitivity for spiral CT angiography of less than 85%, a conventional angiographic strategy yielded a lower mortality but did not yield superior cost-effectiveness. CONCLUSION: The use of spiral CT angiography is likely to reduce the mortality and improve cost-effectiveness in the diagnostic work-up of suspected pulmonary embolism.

Algorithms↗
PubMed1994

Magnetic resonance imaging or metaiodobenzylguanidine scintigraphy for the demonstration of paragangliomas? Correlations and disparities.

Paragangliomas are tumours arising from paraganglionic tissue dispersed from the base of the skull to the pelvic diaphragm. These tumours produce symptoms by secreting catecholamines (functioning tumours) or by local tumour expansion. They can be part of several hereditary disorders. The introduction of magnetic resonance (MR) imaging and metaiodobenzylguanidine (MIBG) scintigraphy has provided new insights into paragangliomas and has tremendously changed the topographic diagnosis of paragangliomas. Both techniques have proven to be adequate in localising paragangliomas. In this report, the performance of these two noninvasive imaging methods in the examination of paragangliomas is compared and the merits and deficits of the two techniques are discussed. Both techniques produce comparable results in the detection of functioning paragangliomas. MR imaging, however, also demonstrates tumours that do not take up MIBG. MR imaging does not involve the use of ionising radiation and is not hampered by medication. Moreover, MR imaging has a higher spatial resolution. Because of these merits it is concluded that for demonstration of paragangliomas, whole-body MR imaging is the preferred and initial method of investigation. MIBG scintigraphy, on the other hand, continues to be a reliable method for non-invasive detection of functioning paragangliomas. At present it is clearly faster in whole-body imaging than MRI and it is definitely patient-friendly (no claustrophobia). It could be reserved for cases where a strong suspicion of a functioning paraganglioma persists, despite normal MR imaging findings, and for cases where doubt exists about the functional activity of one or more multicentric tumours. MIBG scintigraphy must be used in the evaluation of patients referred for iodine-131 MIBG treatment.

3-Iodobenzylguanidine↗
PubMed1991

MR imaging and MIBG scintigraphy of pheochromocytomas and extraadrenal functioning paragangliomas.

To compare the potential of magnetic resonance (MR) imaging and scintigraphy performed with radiotracer-labeled metaiodobenzyl-guanidine (MIBG) in localization and characterization of functioning paragangliomas, the authors analyzed results of both modalities in 33 patients. Overall sensitivity for detection was 91% for MR imaging and 80% for MIBG scintigraphy. MR imaging demonstrated 100% of adrenal paragangliomas and 75% of extraadrenal paragangliomas, whereas MIBG scintigraphy revealed 75% and 88%, respectively. MIBG scintigraphy was more specific in the characterization of paragangliomas than MR imaging (100% vs 82%). However, MR imaging demonstrated nine other lesions not seen on scintigrams. On the basis of their results and other considerations, the authors believe MR imaging is the preferred initial technique when a functioning paraganglioma is suspected.

3-Iodobenzylguanidine↗
PubMedDate not supplied

CT and MR distinction of adenomas and nonadenomas of the adrenal gland.

OBJECTIVE: Because the distinction between adenomas and nonadenomas of the adrenal gland is essential, we investigated which of the following parameters--size, CT attenuation values, MRI signal intensity ratios on T1- and T2-weighted sequences, calculated T2 relaxation times, or T2 relaxation time ratios--provides better discrimination. MATERIALS AND METHODS: We compared these parameters in 44 adrenal masses of 37 patients by means of the Student t test and receiver operating characteristics (ROC) analyses. RESULTS: Only size, CT attenuation values, and signal intensity ratios on T2-weighted MR images of adenomas showed a significant difference from those of nonadenomas. With use of ROC analysis, CT demonstrated a significantly larger area under the curve compared to size and T2 signal intensity ratios, indicating superior performance. CONCLUSION: We found attenuation values on non-contrast-enhanced CT to be the best method in discriminating adrenal adenomas from nonadenomas. Adrenal masses with CT attenuation values below 15 HU warrant no further investigations.

Adenoma↗