Comment on: Quality of Life and Psychological Morbidity in Vitiligo Patients: A Study in a Teaching Hospital from North-East India.

Sir,

This is in reference to the article, Quality of life and psychological morbidity in vitiligo patients: A study in a teaching hospital from North-East India.[1]

The authors have done a commendable job to assess the quality of life in patients of vitiligo. However, I have a few concerns regarding the type of study and methodology being adopted in the present study.

First, the authors have written in their material and methods that the study done was a cross-sectional, descriptive, case-control, hospital-based study.

The epidemiologic studies are either descriptive or analytical studies. Descriptive studies include case reports, case series reports, cross-sectional studies, surveillance studies, and ecological studies whereas analytical studies are either experimental or observational. Case-control and cohort studies are the types of observational studies.[2]

So how can a study be “cross-sectional, that is, descriptive” and “case-control” at the same time?

Further, the authors have detailed the present study as a case-control study. They administered dermatology life quality index and Hamilton depression rating scale to 100 vitiligo patients presenting to the dermatology outpatient department and 50 age and sex-matched healthy controls to assess the impact of the disease on the quality of life of patients suffering from vitiligo and to compare the results with that of healthy control group.[1]

However, in a case-control study, the investigator selects cases with the disease and appropriate controls without the disease and obtains data regarding the “past exposure” to possible etiologic factors in both groups. The hallmark of a case-control study is that it starts from cases and controls and searches for exposure. However, the authors were not intending to find any exposure in the present study. As mentioned, the objective of the present study was to assess the quality of life and to compare the frequency and the level of depression in patients of vitiligo which could only have been assessed prospectively.

The authors should have done a prospective cohort study where subjects who were initially free of depressive disorders should have been selected and then classified according to their exposure to risk factors (vitiligo here). The case-control design uses a different sampling strategy in which the investigators identify the cases and controls which are then compared with respect to the frequency of one or more past exposures (vitiligo is the exposure here and depressive disorder is the disease). If the cases have a substantially higher odds of exposure to a particular factor compared to the control subjects, it suggests an association.[3]