Dear Editor,
The recently published article, “Transcranial direct current stimulation improves quality of life and physical fitness in diabetic polyneuropathy: a pilot double blind randomized controlled trial” by Galeno Ferreira et al. in Journal of Diabetes and Metabolic Disorders (March 2020, 19(6), 327–335) [1] is very interesting and well documented. Authors concluded that transcranial direct current stimulation (tDCS) in patients with diabetic polyneuropathy has improved their physical health, functional capacity, bodily pain and physical functioning. We gathered knowledge after reading this article but noticed some points that need more clarification from the authors.
First, under the methodology section the study design mentioned “a pilot, parallel, sham, randomized double blind” but in the title it is mentioned as “a pilot double blind randomized controlled trial”,it is remain unclear to the readers that what is the actual study design. Instead it should be pretest posttest control group design [2].
Second, under the methodology section authors have mentioned inclusion criteria (1) clinical diagnoses of chronic symmetrical length – dependent sensorimotor polyneuropathy. But it remains unclear that Type 1 diabetes mellitus and Type 2 diabetes mellitus. (2) Aged 18–60 years, but if authors assessed the physical activity level and dynamic balance of the participants, there is a large variability in age group, which may influence the results as the balance is affected by aging. [3] However, under results section, mean age is 60.9 ± 15.26 (active group) and 60.7 ± 9.21 (sham group) [1], it remains again unclear then why authors took age group 18–60 years? Under exclusion criteria (4) amputation is mentioned, but there is a need for specification of the site of the amputation.
Third, Authors have mentioned under outcomes section in 5th paragraph that the Douleur Neuropathique 4 Questionnaire (DN4) was used and considered as dependent variable. But the results of this outcome within and between groups were not reported in the study. Moreover, it is advisable that tDCS can give beneficial results in the relief of neuropathic pain [4].
Fourth, Authors have used 30 s chair stand test for the evaluation of strength of lower extremity and 30 s arm curl test for upper extremity, but in available literature there is no evidence of reliability of these tools in patients with diabetic polyneuropathy. Instead they should have used highly reliable tools such as isokinetic dynamometers [5], as it is high priced not easily available in clinical settings then also it is advisable to use hand held dynamometers in this patient population to measure strength [6].
Lastly, under data analyses section authors have mentioned bonferroni contrast test, chi square test and GEE model were used but the results were not reported completely, so it is perplexing for the readers. In Table 1, authors specify for the baseline analysis of the right ankle brachial index, they have used Mann Whitney U test. It is inappropriate to express these results as mean ± standard deviation, as this test is non parametric. Instead they should have used as median (Interquartile range IQR) or mean (confidence interval) values to express the central tendency for non-normal distribution of data [7]. However, it also needs clarification for the readers that why authors only have used this test for right ankle brachial index? It may be mentioned that right ankle brachial index does not follow normal distribution, that’s why, the author might choose non parametric test for right ankle brachial index.
The work done in this study is beneficial in clinical practice and we appreciate the author’s novel ideas and its accomplishment.
Funding
No funding.
Compliance with ethical standards
Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
Conflict of interest
Authors declared no conflict of interest.
Footnotes
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References
- 1.Ferreira G, Silva-Filho E, de Oliveira A, de Lucena C, Lopes J, Pegado R. Transcranial direct current stimulation improves quality of life and physical fitness in diabetic polyneuropathy: a pilot double blind randomized controlled trial. J Diabetes Metab Disord. 2020;19:327–335. doi: 10.1007/s40200-020-00513-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Portney LG, Watkins MP. Foundations of Clinical Research. 3rd editio. F A Davis company.2015. 196–197 p. ISBN-13: 978–0–8036-4657-5.
- 3.Osoba MY, Rao AK, Agrawal SK, Lalwani AK. Balance And Gait In The Elderly : A Contemporary Review. Laryngoscope Investig Otolaryngol. 2019:143–53. 10.1002/lio2.252 [DOI] [PMC free article] [PubMed]
- 4.Kim YJ, Ku J, Kim HJ, Im DJ, Lee HS, Han KA, Kang YJ. Randomized, Sham Controlled Trial of Transcranial Direct Current Stimulation for Painful Diabetic Polyneuropathy. Ann Rehabil Med. 2013;37(6):766–776. doi: 10.5535/arm.2013.37.6.766. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Services H. Type 2 diabetes, muscle strength, and impaired physical function. Diabetes Care. 2005;28(10):2541–2542. doi: 10.2337/diacare.28.10.2541. [DOI] [PubMed] [Google Scholar]
- 6.Nomura T, Kawae T, Kataoka H, Ikeda Y. Assessment of lower extremity muscle mass , muscle strength, and exercise therapy in elderly patients with diabetes mellitus. Environ Health Prev Med. 2018;23(1):20. doi: 10.1186/s12199-018-0710-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Habibzadeh F. Statistical data editing in scientific articles. J Korean Med Sci. 2017;32:1072–1076. doi: 10.3346/jkms.2017.32.7.1072. [DOI] [PMC free article] [PubMed] [Google Scholar]