Pulsed Electromagnetic Field Therapy: Methodology

Extraneous Variables and Controlling for Them

Extraneous variables are factors that can influence the outcome of a study by affecting the measurement of the variables of the research, as well as the relationships between them (Grove, Gray, & Burns, 2015). In the current study, there might be several extraneous variables. Those which were identified are as follows:

  • The severity of pain before treatment. To account for it, it will be measured and used as a covariate in the ANCOVA.
  • The severity of pain might be influenced by non-neuropathic pain. This will be controlled by using an instrument that differentiates between neuropathic and non-neuropathic pain.
  • The effectiveness of treatment might be influenced by environmental factors; for instance, if some patients do not stay in the hospital during treatment, this may have an impact on the quality of care and treatment effectiveness. This will be addressed by the fact that the patients from both the experimental and the control groups will have different environments, so the error should be approximately the same on the average.

The Instrument

Description and Appropriateness for Addressing the Research Question

The instrument which was selected for the current study is the S-LANSS (Self-Completed Leeds Assessment of Neuropathic Symptoms and Signs pain scale). It is a modification of the LANSS scale which is suitable for patients’ self-assessment. It was chosen over the LANSS scale since it permits for assessing the intensity of the pain (“The S-LANSS Pain Score,” n.d.; Toth & Moulin, 2013, pp. 14, 24-25). The tool includes several questions aimed at determining whether the pain is neuropathic or not (yielding an overall score from 0 to 24, where the values of ≥12 indicate neuropathic pain; this is, in fact, equal to a yes/no answer), as well as an 11-point scale for assessing the intensity of the pain (0=no pain, 10=the most severe pain) (“The S-LANSS pain score,” n.d.).

The research question for the current study is: “In patients aged 30-60 with diabetic neuropathy, how effective is PEMF in reducing pain originating from this condition when compared to analgesics, tricyclic antidepressants, and anti-seizure medication?” Therefore, it is needed to measure the level of patients’ neuropathic pain before and after the treatment, and compare the results across different treatment groups. Because S-LANSS measures the intensity of pain and identifies whether it is neuropathic, it should be adequate for this research.

Validity and Reliability

The S-LANSS tool is estimated to be valid and reliable. As for validity, it is stated that the sensitivity of S-LANSS might vary between 52-57%, and its specificity may fall between 69 and 78%; these numbers depend on how the questionnaire is administered (telephone or e-mail) (Eckeli, Teixeira, & Gouvêa, 2016, p. 21). Because the questionnaire will be administered personally, the sensitivity and specificity may be somewhat different from the given numbers. As for reliability, the instrument is also stated to be reliable (Barbosa, Bennett, Verissimo, & Carvalho, 2013; Eckeli et al., 2016; Spanos, Lachanas, Chan, Bargiota, & Giannoukas, 2015).

Plans for Testing Reliability and Validity

The validity of the proposed instrument can be checked by comparing its results to those of the clinical diagnosis (Eckeli et al., 2016), for instance, one that was obtained via medical tests such as nerve conduction test (NCS) and electromyography (EMG) (Weiss, Weiss, & Silver, 2016). The participants of the study will likely be diagnosed with neuropathic pain before the beginning of the treatment; before the diagnosis is made, it will be possible to administer the questionnaire to them for obtaining the preliminary results about their condition. The results of surveying will be compared to those of the medical tests.

The reliability can be tested by using the test-retest procedure (Grove et al., 2015). It will be possible to administer the S-LANSS survey to the patients twice before starting the treatment to obtain the needed data.

Description of the Intervention

The first group of patients will be administered PEMF to address diabetic neuropathic pains. The patients will be exposed to a unidirectional semi-rectangular waveform with a frequency of 15 Hz and strength of 20 gausses; it will be applied to the soles of the feet with symptoms for 25 minutes. 9 sessions will be made from Monday to Friday. The second group of patients will be given analgesics, tricyclic antidepressants, and anti-seizure medication to address their diabetic neuropathic pains.

Data Collection Procedures

The data will be collected using the S-LANSS instrument. The S-LANSS questionnaires will be administered to patients in whom diabetic neuropathic pains will be suspected, before telling them their diagnosis based on medical tests. This will be done to assess the test-retest reliability of S-LANSS.

Before starting the treatment (either with PEMF or medication), the patients will be asked to complete the S-LANSS questionnaire once again. The obtained scores will be used for checking the test-retest reliability; they also will be employed as the pre-treatment assessment of the levels of neuropathic pain.

After the treatment (either PEMF or medication) is finished (that is, the patients have undergone all the required PEMF sessions, or taken all the medication prescribed according to the plan of the research), the patients will be surveyed once again to assess the post-treatment levels of neuropathic pain.

All the data will be transferred into the electronic format and prepared for further statistical analysis.


Barbosa, M., Bennett, M. I., Verissimo, R., & Carvalho, D. (2013). Cross-cultural psychometric assessment of the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) pain scale in the Portuguese population. Pain Practice, 14(7), 620-624. Web,

Eckeli, F. D., Teixeira, R. A., & Gouvêa, A. L. (2016). Revista do Instituto de Medicina Tropical de São Paulo (Journal of the São Paulo Institute of Tropical Medicine), 2016(17), S20-S22. Web.

Grove, S. K., Gray, J. R., & Burns, N. (2015). Understanding nursing research: Building an evidence-based practice (6th ed.). St. Louis, MO: Elsevier.

Spanos, K., Lachanas, V. A., Chan, P., Bargiota, A., & Giannoukas, A. D. (2015). Validation of the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) questionnaire and its correlation with visual analog pain scales in Greek population. Journal of Diabetes and its Complications, 29(8), 1142-1145. Web.

(n.d.). Web.

Toth, C., & Moulin, D. E. (Eds.). (2013). Neuropathic pain: Causes, management and understanding. Cambridge, UK: Cambridge University Press.

Weiss, L. D., Weiss, J. M., & Silver, J. K. (2016). Easy EMG: A guide to performing nerve conduction studies and electromyography (2nd ed.). Amsterdam, Netherlands: Elsevier.

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