Pitfalls of the novel parameter, n-index
Department of Dermatology, Azadegan Street, Imam Khomeini Hospital, Ahvaz
|How to cite this article:
Feily A, Yaghoobi R. Pitfalls of the novel parameter, n-index. Indian J Dermatol Venereol Leprol 2010;76:562-563
While there are many new indices with interesting, unique attributes to evaluate /rank any researcher, none has been found to be perfect or near perfect.  We read with interest the view point by Namazi and Fallahzadeh published in the May-Jun 2010 issue of Indian Journal of Dermatology Venerology and Leprology.  In their paper, the authors considering field variation described a problem that hampers a fair evaluation of scientific performance. To surmount unequal citations in different fields, the authors suggest a novel index: n-index = Researcher′s h-index divided by the highest h-index of the journals of his/her major field of study. Although this is true, one point raised is that some of the authors have got their h-index from their articles in different areas of science.
The most obvious paradigmic example of that is the inventor of n-index Namazi. At this moment the h-index of Namazi is 9  and one of his publications that has raised his h-index is "Results of the application of intraoperative mitomycin C in dacryocystorhinostomy."  Notably, this article has been published in European Journal of Ophthalmology by 13 times citations  and there is no relationship between above mentioned article and dermatology. Reasonably, it is impossible to divide his h-index by the highest h-index of the journals of his major field of study, dermatology. Similarly being a co-author or being one of the members of a large multi-centric study, being a research associate and co-author of a publication in a journal with a Nobel laureate (with high index - whatever h or n), not related to the area of specialization, will remain as an issue.
It should be pointed out that journals undoubtedly get their h-index from the high quality articles which have been written by influential authors. Accordingly, another criticism raised is the conflict between increasing h-index of the journals of author′s major field of study and decreasing author′s n-index. As an example, well-known authors who have published his/her sublime works in highest h-index journals of his/her major field of study can expect that by increasing citations of his/her articles and journal`s h-index as well, their n-index would have been decreased.
Another criticism raised is that n-index can not be used for author′s publication in multidisciplinary journals. For instance h-index for journal of Nature is 599  which is around 6 times more than 103 - the h-index of Journal of American Academy of Dermatology.  Therefore, for a scientist who has published just 4 but brilliant masterpieces in this journal by more than 4 citations, it would be surely unfair to divide his/her h-index 4 by the h-index of the journal of Nature and to compare with a dermatologist with the same h-index.
However, we agree with Namazi and Fallahzade that field variation creates obstacle to fair evaluation of scientific performance; but given the pitfalls mentioned above, we can neither accept their view point nor advocate that n- index can replace h-index in all proposed indices based on it.
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