The Cochrane Library High quality evidence about the effectiveness of treatments

The Cochrane homepage: use the advanced search option

My query My dog’s vet recommended we give the dog glucosamine as a treatment for his osteoartritis. Did we waste our money 1 by feeding him this expensive supplement along with his dried food? 1 Well, Petplan’s money…

Cochrane’s predictive text facility seems to confirm osteoarthritis as an appropriate search term

Click on the + symbol to open up the next search line

Now enter the name of the treatment

…and click on Go

There are 142 results, divided into different types

The Cochrane reviews are displayed first (if there are any)

These can be subdivided into (completed) reviews, and protocols (currently being written)

To look at different types of studies, (e.g. economic evaluations) just click the appropriate radio button

Returning to the Cochrane review results, I find a review I’d like to read

Click on the title of the review

Various viewing options are available: but the row of tabs is quite helpful for on screen reading

The abstract tab contains two summaries: a scholarly abstract for the healthcare professional,

And a plain language summary for the man in the street

The Figures section is especially interesting.

It allows you to view the meta-analysis diagrams (forest plots)

Clicking on the Cochrane emblem next to Analysis 1.1

Enables you to view this diagram

The librarians can offer assistance in how to interpret forest plots Meanwhile, the following short notes may or may not help

The results of each individual trial are represented as a (green) square, with a black line running though. The position of the square indicates how much of the outcome measure was obtained: the further the square is to the right of the vertical black line, the greater the outcome obtained. The horizontal line running through the square is the confidence interval. Whilst the square indicates the results for the particular set of patients in the trial, the confidence interval indicates where the true effect on the population as a whole may lie.

In the two trials shown here the green square is situated smack on top of the no-difference line, indicating that participants taking glucosamine reported similar amounts of pain to those taking sugar pills.

The rhombus at the bottom of the diagram is the meta-analysis: the result of combining together the results of all the individual trials. The rhombus is situated slightly to the left of the no-difference line. This means that, on balance, participants who took glucosamine reported less pain than those taking sugar pills. (The centre of the rhombus indicates the results for these combined trials. The width of the rhombus suggests the range that may contain the true effect on the population as a whole.)

This suggests that humans with osteoarthritis might gain some measure of pain relief if they take glucoasmine. Although, the review does point out that the results of the meta-analysis may have been swayed by the unusually beneficial results obtained in two of the drugs company sponsored trials. (And bearing in mind the different physiological characteristics of humans and golden retrievers, I am still none the wiser about any benefits my dog may or may not have obtained.)