|Year : 2013 | Volume
| Issue : 3 | Page : 340
Incidence of malignancies in biopsy-proven inflammatory myopathy: Comment and erratum
Sunil K Raina
Department of Community Medicine, Dr. Rajendra Prasad Government Medical College, Tanda, Kangra, Himachal Pradesh - 176 001, India
|Date of Submission||11-May-2013|
|Date of Decision||13-May-2013|
|Date of Acceptance||17-Jun-2013|
|Date of Web Publication||16-Jul-2013|
Sunil K Raina
Department of Community Medicine, Dr. Rajendra Prasad Government Medical College, Tanda, Kangra, Himachal Pradesh - 176 001
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Raina SK. Incidence of malignancies in biopsy-proven inflammatory myopathy: Comment and erratum. Neurol India 2013;61:340
I went through an article entitled "Incidence of malignancies in biopsy-proven inflammatory myopathy" published in your journal (Neurol India 2013; 61:152-5). 
The efforts of the authors are laudable, but I fail to understand how the incidence of malignancies was calculated. Having a look at [Table 1] of the study, what we arrived at is the prevalence of malignancy in biopsy-proven inflammatory myopathy and not incidence. When relatively precise data on the timing of events or losses are available for each individual from a defined cohort (as is the case in this study), incidence density needs to be calculated.  This is expressed as:
The total person-time for the study period is simply the sum of the person-time contributed by each individual.
As incidence encompasses frequency, reference to time is important, and that is why, incidence is not expressed as percentages (as done by the authors) but as person-time.
The authors actually have done a commendable job in data retrieval and finding an association between malignancies and inflammatory myopathy.
[Table 1] of the study is given below:
| » References|| |
|1.||Kannan MA, Sundaram C, Uppin M, Mridula R, Jabeen SA, Borgohain R. Incidence of malignancies in biopsy-proven inflammatory myopathy. Neurol India 2013;61:152-5. |
|2.||Szklo M, Nieto FJ. Measuring disease occurrence. In: Szklo M, Nieto FJ, editors. Epidemiology beyond the basics. 2 nd ed. Sudbury, MA: Jones and Bartlett Publishers, Inc; 2007. p. 47-76. |