Applying 'evidence-based medicine' theory to interventional radiology. Part 2: a spreadsheet for swift assessment of procedural benefit and harm.
OBJECTIVE
To design a spreadsheet program to analyse interventional radiology (IR) data rapidly produced in local research or reported in the literature using 'evidence-based medicine' (EBM) parameters of treatment benefit and harm.


METHODS
Microsoft Excel(TM)was used. The spreadsheet consists 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 the EBM assessment of therapeutic benefit and harm. Validity criteria are described. These include the assessment of the adequacy of sample size in the detection of possible procedural complications. A contingency (2 x 2) table for raw data on comparative outcomes in treated patients and controls has been incorporated. Formulae for EBM calculations are related to these numerators and denominators in the spreadsheet. The parameters calculated are benefit - relative risk reduction, absolute risk reduction, number needed to treat (NNT). Harm - relative risk, relative odds, number needed to harm (NNH). Ninety-five per cent confidence intervals are calculated for all these indices. The results change automatically when the data in the therapeutic outcome cells are changed. A final section allows the user to correct the NNT or 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.


CONCLUSIONS
A spreadsheet is useful for the rapid analysis of the clinical benefit and harm from IR procedures.
Maceneaney
P M
PM
Departments of Radiology, St. Vincent's University Hospital, Elm Park, Dublin 4, Ireland.
Malone
D E
DE
D019317:Evidence-Based Medicine / Q000379:methods*; D006801:Humans; D015642:Radiology, Interventional; D015203:Reproducibility of Results; D018570:Risk Assessment; D018401:Sample Size; D012985:Software Design; D013223:Statistics as Topic