Applying 'evidence-based medicine' theory to interventional radiology. Part 2: A spreadsheet for swift assessment of procedural benefit and harm

AIM: To design a spreadsheet program to analyse interventional radiology (I R) data rapidly produced in local research or reported in the literature us ing 'evidence-based medicine' (EBM) parameters of treatment benefit and har m. MATERIALS AND METHODS: Microsoft Excel(TM) was used, The spreadsheet consis ts of three worksheets, The first shows the 'Levels of Evidence and Grades of Recommendations' that can be assigned to therapeutic studies as defined by the Oxford Centre for EBM. The second and third worksheets facilitate th e EBM assessment of therapeutic benefit and harm. Validity criteria are des cribed. These include the assessment of the adequacy of sample size in the detection of possible procedural complications. A contingency (2x2) table f or ram data on comparative outcomes in treated patients and controls has be en incorporated. Formulae for EBM calculations are related to these numerat ors and denominators in the spreadsheet, The parameters calculated are bene fit relative risk reduction, absolute risk reduction, number needed to trea t (NNT). Harm - relative risk, relative odds, number needed to harm (NNH). Ninety-five per cent confidence intervals are calculated for all these indi ces. The results change automatically when the data in the therapeutic outc ome cells are changed. A final section allows the user to correct the NNT o r NNH in their application to individual patients. RESULTS: This spreadsheet can be used on desktop and palmtop computers, The MS Excel(TM) version can be downloaded via the Internet from the URL ftp:/ /radiography.com/pub/TxHarm00.xls. CONCLUSION: A spreadsheet is useful for the rapid analysis of the clinical benefit and harm from IR procedures, MacEneaney, P. M. & Malone, D. E. Clin ical Radiology 55 938-945. (C) 2000 The Royal College of Radiologists.