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| Year : 2015 | Volume
: 63
| Issue : 4 | Page : 640 |
Deciding on the study design
Sunil K Raina
Department of Community Medicine, Dr. Rajendra Prasad Government Medical College, Tanda, Kangra, Himachal Pradesh, India
| Date of Web Publication | 4-Aug-2015 |
Correspondence Address:
Sunil K Raina
Department of Community Medicine, Dr. Rajendra Prasad Government Medical College, Tanda, Kangra, Himachal Pradesh
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0028-3886.162134
How to cite this article:
Raina SK. Deciding on the study design. Neurol India 2015;63:640 |
Sir,
This is in reference to the article entitled "Nonmotor symptoms in an Indian cohort of Parkinson's disease patients and correlation of progression of nonmotor symptoms with motor worsening" published in Neurology India (2015; 63:166-74).[1] The authors deserve appreciation for their efforts. However, I have a few concerns with this study. The study has been conducted with the aim to validate the nonmotor score scale in an Indian cohort of Parkinson's disease patients for recording the nonmotor score of the disease. [1] The authors in their title have also mentioned the correlation of progression of nonmotor symptoms with motor worsening. The cohort study design is ideally suited for this type of study and the authors have rightly mentioned this fact in their title. By its design, a cohort study is a longitudinal study. However, the authors in the section on "material and methods" under the heading "study design" go on to write that this was a cross-sectional, single-center, open-label, one-point-in-time evaluation study conducted from 2009 to 2011. [1] Here, I am unable to understand how a cross-sectional, single-center, open-label, one-point-in-time evaluation study can study the correlation of progression. For that, a longitudinal follow-up study will be required. No doubt, a cohort study design can be used with different recruitment points for the purpose of this study but one-point evaluation may not be able to detail progression. This takes me to my second point of concern. The authors report that 45 controls were recruited for the purpose of this study. [1] They state that the controls for this study were recruited from among the relatives of the patients visiting the outpatient department. They further state that they were age- and sex-matched with the cases. Now, recruiting controls makes this a case-control study, which is not the same as a cohort design. As per the demands of the study, was there really a need to recruit controls? This is because it may not be possible to establish the timeline of exposure to the disease outcome in the setting of a case-control study than within a prospective cohort study design, where the exposure is determined prior to following the subjects over time in order to ascertain their outcome status. Finally, the number of cases and controls does not match in this study, which is necessary in an age- and sex-matched case-control study. [2]
| » References | |  |
| 1. | Ravan A, Ahmad FM, Chabria S, Gadhari M, Sankhla CS. Non-motor symptoms in an Indian cohort of Parkinson′s disease patients and correlation of progression of non-motor symptoms with motor worsening. Neurol India 2015;63:166-74.  [ PUBMED]  |
| 2. | Raina SK. Validity versus reliability. Neurol India 2015;63:291-2. [ PUBMED] |
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