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Centre for Evidence-
Based Medicine

Therapy: Clinical Scenario

You are a school nurse who regularly visits a number of elementary and middle schools (children aged 5 to 13 years) in your region. It is cold and flu season once again. One of the teachers stops you in the hall to ask you a question about his 10- year old daughter who also has a cold. He has heard that zinc lozenges can help to relieve cold symptoms and wonders if they really do work and if it is OK to give them to children.

With him you formulate the question, in children with colds are zinc lozenges safe and effective for relief of cold symptoms?

Searching terms and evidence source:
You do a search of the Cochrane database (Issue 1, 1999) to see if any systematic reviews are available on the topic. Using the search terms "zinc" and "cold", you find no reviews. You then do a quick search of Best Evidence 3 using the same search terms and find 1 study that looked at the effectiveness of zinc lozenges for colds - unfortunately, the sample consisted of adults only. Not to be discouraged, you decide to do a search in MEDLINE using PubMed (available on the Internet). You do an Advanced Search using the terms "zinc AND cold*" and come up with 233 citations - a bit more than you have time to review. You add the search term "child*" to your previous search and your search result is reduced to 13 citations. Having been a good student of critical appraisal, you know that the best evidence to support a decision about treatment effectiveness usually comes from randomized controlled trials. So once more, you limit your search result by adding the term "randomized controlled trial" - 4 trials remain. One of these trials, a study by Macknin et al ( JAMA 1998;279:1962-7 ) seems to be right on target.

Read the article and decide:

  1. Is the evidence from this randomised trial valid?
  2. If valid, is this evidence important?
  3. If valid and important, can you apply this evidence in caring for your patient?

Continue to completed worksheet