Journal of Postgraduate Medicine
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Year : 2016  |  Volume : 62  |  Issue : 1  |  Page : 51-52  

Calculating incidence in cross-sectional studies

SK Raina 
 Department of Community Medicine, Dr. Rajendra Prasad Government Medical College, Tanda, Himachal Pradesh, India

Correspondence Address:
S K Raina
Department of Community Medicine, Dr. Rajendra Prasad Government Medical College, Tanda, Himachal Pradesh
India




How to cite this article:
Raina S K. Calculating incidence in cross-sectional studies.J Postgrad Med 2016;62:51-52


How to cite this URL:
Raina S K. Calculating incidence in cross-sectional studies. J Postgrad Med [serial online] 2016 [cited 2019 Oct 18 ];62:51-52
Available from: http://www.jpgmonline.com/text.asp?2016/62/1/51/173217


Full Text

Sir,

I went through with interest the article entitled "Incidence and factors associated with medication nonadherence in patients with mental illness: A cross-sectional study" published in the "Journal of Postgraduate Medicine" (2015; 16:251-6). [1]

The authors have conducted a cross-sectional study in the outpatient psychiatric department of a tertiary care private hospital over a period of 1 year and followed up the patients receiving at least one psychotropic medication for at least 1 month. The authors concluded that the overall incidence of medication nonadherence in patients with mental illness was 43%. I have concerns regarding the calculation of incidence for which reference to time is important. [2]

The authors have actually provided us with an estimate of the proportion of nonadherence among patients on psychotropic medication and not incidence. As incidence involves a reference to time; it is not expressed as a percentage (as done by the authors) but as person-time. [3] In contrast, the proportion in statistics refers to the fraction of the total that possesses a certain attribute such as nonadherence in case of this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Lucca JM, Ramesh M, Parthasarathi G, Ram D. Incidence and factors associated with medication nonadherence in patients with mental illness: A cross-sectional study. J Postgrad Med 2015;61:251-6.
2Szklo 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.
3Raina SK. Incidence of malignancies in biopsy-proven inflammatory myopathy: Comment and erratum. Neurol India 2013;61:340.

 
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