What is Visual Rx?
Visual Rx has been updated to version 3 in September 2008. To see how the programme has been improved please look at “What’s new” in the Visual Rx help file.
Visual Rx is designed to help in the process of translation of evidence into practice. The benefits and risks of treatment from clinical trials tend to be presented as relative measures, for example statin treatment may reduce the risk of suffering a cerebro-vascular event by one quarter (or 25%). This finding seems to be true for patients at low and high risk of such events, so it is a useful generalisation. However, the impact on an individual patient will vary according to their pre-existing risk. To apply this evidence to individuals means translation of the relative measure into an absolute measure (so a 20% risk over 10 years without statins would fall to a 15% risk if statins are taken).
Visual Rx is particularly useful in relation to the results of Cochrane Systematic Reviews which are presented on the Cochrane Library. The data & analyses can be reached for an individual review on the Library by scrolling down the menu on the left of the review and clicking under “Supplementary Information” on the Data & Analyses link. The data can be found for each outcome by double-clicking on the individual lines on the summary screen, and the overall pooled Odds Ratio or Risk Ratio (with its 95% Confidence Interval) is also shown for each outcome in the column at the right hand end of the table.
Absolute treatment effects can only be calculated for dichotomous outcomes (marked on the summary screen as a blue box) and the results may well be presented as an Odds ratio which is shown in bold type at the bottom right corner of the Forest plot with its 95% confidence interval in brackets. This pooled Odds Ratio can be entered into Visual Rx, together with the desired control event rate. This may be the total number of events in the control group divided by the total number in the control arms of the included trials (which is in bold at the foot of the control arm) or may be a different figure from other studies to represent specific groups of patients. Visual Rx is designed to work with a percentage figure entered in the Control Event rate on the data entry screen.
Other statistical methods are available in the Cochrane Library, but not all methods are equally reliable and you may wish to consult the help files before deciding to use Risk Ratios in Visual Rx. Odds Ratios are invariant to the choice of entering data as beneficial or adverse outcomes, in contrast to Risk Ratios that give different answers for each.