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Clinical Utility Index Calculator
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Qualitative and Quantitative Clinical Utility of Diagnostic and Screening TestsAlex J Mitchell ajm80@le.ac.uk
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Instructions: enter your data from diagnostic/screening test results in green cells in section a. All results are automatically calculated b) accuracy c) utility
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a) User Data Entryb) Accuracy Statistics
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Lower CIUpper CITPFNTNFPTrue Depression (gold stand)Detected DepressionSensitivitySECIMissed Depressions (False Negatives)True Non-DepressionsDetected non-DepressedSpecificitySECIFalse PositivesPPVSECINPVSECIPrev (D /Total)Utility (+) [SexPPV]SECIUtility (-) [Sp x NPV]SECICU+ InterpretationCU- InterpretationCorrect ID/100Efficiency Testlikelihood ratio (LR+) = sensitivity / (1-specificity)likelihood ratio (LR-) = (1-sensitivity) / specificity
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Enter Total # Cases:2677Sensitivity =>12.7%11.5%14.0%3412336.00146213782.00267734112.7%0.6%1.3%2336.0018403.001462179.4%0.3%0.6%3782.008.3%0.4%0.8%86.2%0.3%0.5%0.1270.0110.0000.0000.6850.0000.000vPoorGood70.9811.830.621.10
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Enter # Cases Detected:341Specificity =>79.4%78.9%80.0%
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Enter Total # Non-Cases:18403Positive Predictive Value = >8.3%7.4%9.1%
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Enter # Cases Detected:14621Negative Predictive Value = >86.2%85.7%86.7%
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Likelihood Ratio +ve =>0.62
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Likelihood Ratio -ve =>1.10
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I developed the clinical utility index in 2007 in order to take into account both occurrence
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and discrimination. Both are important aspects of test performance for clinicians. Further
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it is vital to realize that test results can be valuable both when positive and negative. The Test Score % =>71.0
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product of sensitivity and PPV is only a useful calculation when a positive result of a test is
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under scrutiny. A mirror image calculation namely specificity x NPV is recommended when Prevalence = >12.7%
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a negative test is under scrutiny. In the case of a high PPV or high NPV, a correction is needed
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for occurrence of that test in each respective population. Take for example the occurrence Data check =>Looks OK
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of all five symptoms from DSM-IV as a “test” for depression. In those who test positive
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(that is those who suffer all five symptoms) let us say the PPV is hypothetically 88%
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but often actually having all five symptoms is rare (say 28%) in clinical practice. Any test c) Utility Statistics
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with a high PPV will be devalued if it occurs rarely in true cases. Clinically relevant rule in
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accuracy can be considered a product of the PPV and sensitivity and in this example the CUI+ Clinical Utility +Ve =>vPoorLower CIUpper CI
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for all five symptoms is 0.88 x 0.28 = 0.32. Now consider the calculation needed for ruling-out 0.0110.0100.011
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a diagnosis. For example the absence of the symptom loss of drive might have a high NPV of
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96% but might only be absent (negative) in 70% of non-depressed patients. Thus the negative
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clinical utility index (CUI-) would be 0.96 x 0.70 = 0.67. To help with the application of this indexClinical Utility -Ve =>GoodLower CIUpper CI
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I proposed scores can be converted into qualitative grades as follows: 0.6850.6850.685
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excellent utility >= 0.81, good utility >=0.64 and fair utility >=0.49 and poor utility < 0.49
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d) Citations
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1. Mitchell AJ. The clinical significance of subjective memory complaints in the diagnosis of mild cognitive impairment and dementia: a meta-analysis. Int J Geriatr Psychiatry. 2008 Nov;23(11):1191-202.
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2. Pentzek M, Wollny A, Wiese B et al AgeCoDe Study Group. Apart from nihilism and stigma: what influences general practitioners' accuracy in identifying incident dementia? Am J Geriatr Psychiatry. 2009 Nov;17(11):965-75.
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3. Goncalves et al. Case finding in dementia: comparative utility of three brief instruments in the memory clinic setting. Int Psychogeriatr. 2011 Jan 12:1-9. [Epub ahead of print]
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4. Mitchell AJ. 5. How Do We Know When a Screening Test is Clinically Useful? In Screening for Depression in Clinical Practice: An Evidence-Based Guide (Eds) Alex J. Mitchell and James C. Coyne ISBN10: 0195380193 OUP 2009
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5. R. Rhys Davies and Andrew J. Larner. Addenbrooke’s Cognitive Examination (ACE) and Its Revision (ACE-R). In A.J. Larner (ed.), Cognitive Screening Instruments, DOI 10.1007/978-1-4471-2452-8_4, © Springer-Verlag London 2013
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6. Mitchell AJ. Sensitivity × PPV is a recognized test called the clinical utility index (CUI+). Eur J Epidemiol. 2011 Mar;26(3):251-2; author reply 252. Epub 2011 Mar 26.
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