26 April 2017
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Critical Appraisal: Do I have good quality evidence? Part 1 of 2: The H-Index.

Critical Appraisal: Do I have good quality evidence? Part 1 of 2: The H-Index.

Critical Appraisal of any paper is difficult if you don’t know how to determine if something is good or not! This 2 part article will aim to help you decifer whether you have found yourself good quality evidence. In part 1 we will be helping you understand the measure of authors, the H-Index.

Depending on which dental school you are at, you will be taught that evidence is ranked in a hierarchy of 5 or 7 tiers.

–Images of tiers.

You’re going to be looking for case controlled studies, Random Control trials and Systematic reviews for your good quality evidence which you can cite in your work.

So you have your assignment, and you need evidence to back up your argument. You’ve trawled the whole of PubMed and Medline and found two papers with your exact essay question, but they have conflicting conclusions. So how do you know which one to use?

The validity, if you like, of the paper you have, centres on two main measurable criterion.

  • The h-index of the Author
  • The Impact Factor of the Journal within which it is published. 

So how do you know if an Author is a good author and if the Journal is a good Journal?

In this article, we will focus on the Author.

Authors are recognised based on something called the h-index. This is an integer that illustrates the number of citations an author receives. This, in a roundabout way, tells us how many other writers use and cite information originally published by the author of your paper.

How is it calculated? 

Let’s call our author Mr. X. Mr. X receives an h-index of 1 if a single paper of theirs is cited -by another author- once. Simple enough.

To progress to an h-index of 2, he will require 2 papers, cited twice each. For h-index of 3, 3 papers cited 3 times each, and so on and so forth. As you can see, it takes a lot of papers and a lot of citations for Mr. X to reach a high h-index.

Let us assume Mr.X has an h-index of 39. The first thing we know is that Mr.X has published at least 39 papers (He may have a 40th paper that has been cited 39 times, in which case he will need one more citation for that paper to push his h-index to 40). The second thing we know is that all of those 39 papers have at least 39 other authors deeming Mr.X’s work worthy of a mention in their own research paper. So you know you have a reliable source of information.

How do I find an author’s h-index?

For the purposes of this article, we will search for Edwina A.M. Kidd, author of widely respected textbooks such as Pickard’s Manual of Operative Dentistry and The Essentials of Dental Caries.

First of all, we can find h-index’s and a wide variety of other nuggets of information on a website called www.scopus.com

To log in you can either use the institution finder to find your university on the website (circled) or log in through your university system. This will usually consist of logging into your university account and navigating through the library sections in search for Scopus.com. You may find help with this through your University Intranet.

Scopus.com login page. Either directly through scopus or through your University website.

You will then find yourself presented with a search form. Type the name of the author in the first search bar and look for “Author” in the dropdown menu. Then click “Search”.

The search form; make sure you click on “Author” in the dropdown menu.

As it happens, Scopus finds only one paper written by Edwina Kidd and it turns out to be quite easy for us to find her. In cases where the author has a common name, there are “limit to” options on the left sidebar. If you know the year of publication, the subject area, and whether the author is affiliated with a certain university, it makes it a little easier to find the right “J. Smith”.

Search results. In the left hand column, you can whittle down your results if there are too many.

You then click on EAM Kidd, and this will bring up Edwina Kidd’s profile. The h-index can be found under the “Research” column amongst other information that you may need to know. As we can see, Edwina Kidd has a h-index of 21, very impressive indeed. You can also click on the h-index Graph to see how many other papers E.Kidd has published and how many citations they have all received.

Edwina Kidd’s Profile on scopus.com.

Obviously, a low h-index does not automatically signal poor evidence. It may be that an author has not been publishing papers for long enough for them to have a high h-index. To have a more thorough idea of whether the research conclusions from the paper you have found is any good, it also depends on which Journal it has been published on.

Part 2 of this series shows us how to find out whether a Journal is more like the Daily Mail or the Telegraph.