Weak evidence for radix astragali in treating diabetic retinopathy

Radix astragali
Radix astragali is a traditional Chinese medicine made from dried roots of  that has been widely used for the treatment of diabetes.  This systematic review set out to establish if there is any clinical evidence to support its use in treating diabetic retinopathy.

Clinical question

In people with diabetic retinopathy (DR), does radix astragali, compared with placebo or alternative herbal medicines, improve visual acuity?

Progression of DR was assessed by reports of visual acuity and fundus manifestations.  The reviewers also looked at glycaemic control.


The reviewers searched Medline, EMBASE, The Cochrane Library, Current Controlled Trials and several databases of traditional Chinese medicines for randomised trials on radix astragali in the treatment of diabetic retinopathy.

Two independent reviewers assessed the relevance and quality of studies, and extracted data relating to the outcomes.  These data were pooled in a meta-analysis.


16 controlled trials were found, comprising 977 patients.  The trials were assessed as being of poor quality.  Sample sizes were low, allocation methods were poor, there was substantial loss to follow-up and there was some variation in the way trials recorded visual acuity.

However, the pooled analysis showed that:

the improvement of visual acuity in radix astragali group was significantly better than that of control group (WMD 0.20, 95% CI [0.09, 0.30]).


  • This was a good quality systematic review of a poor quality evidence base.
  • It seems likely that they found all of the evidence available at the time of the search (June 2010).
  • There was significant statistical heterogeneity between the results of the trials.
  • The reviewers performed a sensitivity analysis which suggested that the result may not have been caused by bias from poor quality studies.
  • However, further research is needed with larger cohorts of patients and more rigorous methods to confirm this tentative conclusion.  These studies should examine duration of effect, adverse effects and dosage.



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I am an information scientist with an interest in making knowledge from systematic research more accessible to people who need it. This means you. I've been attempting this in the area of Evidence-Based Health Care since 1995. So far the results have been mixed. For some reason we expected busy clinicians to search databases and appraise papers instead of seeing patients. We also expected publishers to make the research freely available to the people who paid for it.. Ha! Hence The National Elf service.

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