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      A comparison of the Accuracy of Ultrasound and Computed Tomography in common diagnoses causing acute abdominal pain

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          Abstract

          Objectives

          Head-to-head comparison of ultrasound and CT accuracy in common diagnoses causing acute abdominal pain.

          Materials and methods

          Consecutive patients with abdominal pain for >2 h and <5 days referred for imaging underwent both US and CT by different radiologists/radiological residents. An expert panel assigned a final diagnosis. Ultrasound and CT sensitivity and predictive values were calculated for frequent final diagnoses. Effect of patient characteristics and observer experience on ultrasound sensitivity was studied.

          Results

          Frequent final diagnoses in the 1,021 patients (mean age 47; 55% female) were appendicitis (284; 28%), diverticulitis (118; 12%) and cholecystitis (52; 5%). The sensitivity of CT in detecting appendicitis and diverticulitis was significantly higher than that of ultrasound: 94% versus 76% ( p < 0.01) and 81% versus 61% ( p = 0.048), respectively. For cholecystitis, the sensitivity of both was 73% ( p = 1.00). Positive predictive values did not differ significantly between ultrasound and CT for these conditions. Ultrasound sensitivity in detecting appendicitis and diverticulitis was not significantly negatively affected by patient characteristics or reader experience.

          Conclusion

          CT misses fewer cases than ultrasound, but both ultrasound and CT can reliably detect common diagnoses causing acute abdominal pain. Ultrasound sensitivity was largely not influenced by patient characteristics and reader experience.

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          Most cited references22

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          Bias in sensitivity and specificity caused by data-driven selection of optimal cutoff values: mechanisms, magnitude, and solutions.

          Optimal cutoff values for tests results involving continuous variables are often derived in a data-driven way. This approach, however, may lead to overly optimistic measures of diagnostic accuracy. We evaluated the magnitude of the bias in sensitivity and specificity associated with data-driven selection of cutoff values and examined potential solutions to reduce this bias. Different sample sizes, distributions, and prevalences were used in a simulation study. We compared data-driven estimates of accuracy based on the Youden index with the true values and calculated the median bias. Three alternative approaches (assuming a specific distribution, leave-one-out, smoothed ROC curve) were examined for their ability to reduce this bias. The magnitude of bias caused by data-driven optimization of cutoff values was inversely related to sample size. If the true values for sensitivity and specificity are both 84%, the estimates in studies with a sample size of 40 will be approximately 90%. If the sample size increases to 200, the estimates will be 86%. The distribution of the test results had little impact on the amount of bias when sample size was held constant. More robust methods of optimizing cutoff values were less prone to bias, but the performance deteriorated if the underlying assumptions were not met. Data-driven selection of the optimal cutoff value can lead to overly optimistic estimates of sensitivity and specificity, especially in small studies. Alternative methods can reduce this bias, but finding robust estimates for cutoff values and accuracy requires considerable sample sizes.
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            Meta-analysis of randomized controlled trials on the safety and effectiveness of early versus delayed laparoscopic cholecystectomy for acute cholecystitis.

            : In many countries laparoscopic cholecystectomy for acute cholecystitis is mainly performed after the acute episode has settled because of the anticipated increased risk of morbidity and higher conversion rate from laparoscopic to open cholecystectomy. : A systematic review was performed with meta-analysis of randomized clinical trials of early laparoscopic cholecystectomy (ELC; performed within 1 week of onset of symptoms) versus delayed laparoscopic cholecystectomy (performed at least 6 weeks after symptoms settled) for acute cholecystitis. Trials were identified from The Cochrane Library trials register, Medline, Embase, Science Citation Index Expanded and reference lists. Risk ratio (RR) or mean difference was calculated with 95 per cent confidence intervals (c.i.) based on intention-to-treat analysis. : Five trials with 451 patients were included. There was no significant difference between the two groups in terms of bile duct injury (RR 0.64 (95 per cent c.i. 0.15 to 2.65)) or conversion to open cholecystectomy (RR 0.88 (95 per cent c.i. 0.62 to 1.25)). The total hospital stay was shorter by 4 days for ELC (mean difference -4.12 (95 per cent c.i. -5.22 to -3.03) days). : ELC during acute cholecystitis appears safe and shortens the total hospital stay. Copyright (c) 2009 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd.
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              Systematic review: computed tomography and ultrasonography to detect acute appendicitis in adults and adolescents.

              Although clinicians commonly use computed tomography or ultrasonography to diagnose acute appendicitis, the accuracy of these imaging tests remains unclear. To review the diagnostic accuracy of computed tomography and ultrasonography in adults and adolescents with suspected acute appendicitis. The authors used MEDLINE, EMBASE, bibliographies, review articles, textbooks, and expert opinion to retrieve English- and non-English-language articles published from 1966 to December 2003. The authors included prospective studies evaluating computed tomography or ultrasonography followed by surgical confirmation or clinical follow-up in patients at least 14 years of age with suspected appendicitis. One assessor (for non-English-language studies) or 2 assessors (for English-language studies) independently reviewed each article to abstract relevant study characteristics and results. Twelve computed tomography studies and 14 ultrasonography studies met inclusion criteria. Computed tomography had an overall sensitivity of 0.94 (95% CI, 0.91 to 0.95), a specificity of 0.95 (CI, 0.93 to 0.96), a positive likelihood ratio of 13.3 (CI, 9.9 to 17.9), and a negative likelihood ratio of 0.09 (CI, 0.07 to 0.12). Ultrasonography had an overall sensitivity of 0.86 (CI, 0.83 to 0.88), a specificity of 0.81 (CI, 0.78 to 0.84), a positive likelihood ratio of 5.8 (CI, 3.5 to 9.5), and a negative likelihood ratio of 0.19 (CI, 0.13 to 0.27). Verification bias and inappropriate blinding of reference standards were noted in all of the included studies. The summary assessment of the diagnostic accuracy for both tests was limited by the small number of studies, heterogeneity among study samples, and poor methodologic quality in the original studies. Computed tomography is probably more accurate than ultrasonography for diagnosing appendicitis in adults and adolescents. Prospective studies that apply gold standard diagnostic testing to all study participants would more reliably estimate the true diagnostic accuracy of these tests.
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                Author and article information

                Contributors
                +31-20-5662630 , +31-20-56692119 , a.vanranden@amc.uva.nl
                Journal
                Eur Radiol
                European Radiology
                Springer-Verlag (Berlin/Heidelberg )
                0938-7994
                1432-1084
                2 March 2011
                2 March 2011
                July 2011
                : 21
                : 7
                : 1535-1545
                Affiliations
                [1 ]Department of Radiology (suite G1-227), Academic Medical Centre, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
                [2 ]Department of Surgery, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
                [3 ]Department of Radiology, St Antonius Hospital, Koekoekslaan 1, 3435 CM Nieuwegein, The Netherlands
                [4 ]Department of Surgery, St Antonius Hospital, Koekoekslaan 1, 3435 CM Nieuwegein, The Netherlands
                [5 ]Department of Radiology, Gelre Hospitals, Albert Schweitzerlaan 31, 7334 DZ Apeldoorn, The Netherlands
                [6 ]Department of Surgery, Gelre Hospitals, Albert Schweitzerlaan 31, 7334 DZ Apeldoorn, The Netherlands
                [7 ]Department of Radiology, University Medical Centre, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
                [8 ]Department of Radiology, Tergooi Hospitals, Van Riebeeckweg 212, 1213 XZ Hilversum, The Netherlands
                [9 ]Department of Clinical Epidemiology, Biostatistics, and Bioinformatics, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
                Article
                2087
                10.1007/s00330-011-2087-5
                3101356
                21365197
                8abe718b-7acb-40e3-ac9f-d5fcf51b88b2
                © The Author(s) 2011
                History
                : 9 September 2010
                : 6 December 2010
                : 15 December 2010
                Categories
                Gastrointestinal
                Custom metadata
                © European Society of Radiology 2011

                Radiology & Imaging
                appendicitis,acute abdominal pain,ultrasound,emergency department,computed tomography

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