How well do we measure pain and physical functions in people with diabetic nerve pain?

Diabetes is a serious complex health condition and can affect the entire body. Although diabetes can be managed well, the complications are still a challenge for the patients and health caregivers. The complications include heart attack, stroke, kidney disease, limb amputation, depression, anxiety and blindness. On top of all these complications, diabetes is also considered to be the most common cause of nerve pain worldwide.

Nerve pain (neuropathic pain, neuropathy) is caused by damage, injury or dysfunction of nerves due to trauma, surgery, disease (for example- diabetes) or chemotherapy.

Patients suffering from diabetic neuropathy often describe their pain as burning, painful, cold or resembling electric shocks, and may be associated with tingling, pins and needles, and numbness or itching. This pain may reduce quality of life by loss of sensation, and limitation of physical activity levels overall leading to serious disability. Being a physiotherapist, I was always interested in assessing pain and physical function of a patient. These two, were the most common concerns for patient’s and a reason to visit a specialist. However, for diabetic neuropathic pain, unfortunately there are no recommended methods for measuring these symptoms.

To develop my own understanding of the topic, I started going through available literature. I can’t thank enough my supervisory team, for their continuous support and guidance throughout this journey. I got the impression that while there is no permanent cure for diabetic nerve pain, you can still live an enjoyable life by learning about the condition and effectively managing it.

The first step of optimizing management was to successfully assess and diagnose the condition. From the literature, it was evident that with the advancement of digital technology, it was fairly easy to trace the location of nerve pain. Clinical examination can reveal abnormal sensory functions in the area of pain. In clinical situations, to measure these symptoms, generic and disease-specific scales/questionnaires (also known as measures) can be helpful. However, in order to capture a real change in a behavior of pain or physical function, the used questionnaire should be reliable (within acceptable limits of error).

To further add on to my confusion, there were a whole plethora of measures, which have been used in the past for nerve pain assessment, with different magnitudes of reliabilities. My question was which one is the most reliable measure to use in people with diabetes? Overall aim of my PhD was to check the properties of all the available measures, and also recommend a set of measures for the assessment of pain and physical function in diabetic-related nerve pain (Mehta et al., 2015).

With that question in mind, I designed a series of research projects. It was important to plan studies using a multiple-step approach to fullfil its objectives. As the first step, I reviewed all the published research studies to explore a range of measures available to capture the pain and physical functions in patients with general nerve pain (Mehta et al., 2014a). I found that there was no single known measure available for assessing these domains. As the next step, I reviewed the available studies to assess the reliability of the identified pain and physical function measures in general nerve pain conditions (Mehta et al., 2016).

Surprisingly, that the most commonly used pain and physical function measures were either not assessed for reliability, or studies were not up to the mark when evaluated for their quality. What a gap! To my astonishment, even the studies with high methodological quality used two measures for pain and physical function in a nerve pain population (modified Brief Pain Inventory for Diabetic Peripheral Neuropathic pain scale: mBPI-DPN and short form Screening of Activity Limitations and Safety Awareness scale: sSALSA). As these two measures were not assessed for all of the properties, the evaluation of missing properties of these two identified measures was required before any final recommendation could be made.

The same year I was able to attend and present at a conference on Pain in Europe, held at Florence, Italy (Figure 1). Sharing the findings of my study with the international audience, made me more confident about my next step, as I was aware of what needed to be done.

I developed a longitudinal study focusing on evaluating the reliability of the identified measures: pain (mBPI-DPN scale) and physical function (sSALSA scale), in a diabetes-induced nerve pain population (Mehta et al., 2014b). With a great help of people from around New Zealand, within three months, I was able to collect data from 38 participants (Figure 2). A special token of appreciation to all the branches of Diabetes New Zealand, for spreading the word about this research to the community!

The results of this final study showed that both pain and physical function measures can be used at different times and would again yield the same results (test-retest reliability), which were correlated. However, the computational methods used in different methodologies to calculate responsiveness (ability to detect change over time) for the mBPI-DPN and the sSALSA scales varied, hence the magnitude of change scores also varied (Mehta et al., 2018). This situation clearly raised the issue of the practical utility of such scores in clinical and research applications. But this will be the next step to do, exceeding the scope of my PhD.

To summarize, I was able to figure out that these two measures are the best ones to assess pain (mBPI-DPN questionnaire) and physical function (sSALSA questionnaire) in people with diabetic nerve pain. However, research is a continuous journey, there is still much more work which needs to be done!

A research journey by Dr. Poonam Mehta

Poonam

Academic readings:

• Mehta P., Claydon L., Hendrick P., Cook C., & Baxter G. D. (2014a) Outcome Measures in Randomized Controlled Trials of Neuropathic Pain Conditions: A Systematic Review of Systematic Reviews and Recommendations for Practice. Clin J Pain. www.ncbi.nlm.nih.gov/pubmed/24662497.
• Mehta P., Claydon L. S., Mani R., Hendrick P., and Baxter G. D. (2014b). Investigating the psychometric properties of patient reported outcome measures in individuals with chronic diabetic neuropathic pain: prospective longitudinal cohort study protocol. Physical Therapy Reviews, 19(6), 440-446. DOI: 10.1179/1743288X14Y.0000000157.
• Mehta P. (2015). Neuropathic pain: Outcome measures and their psychometric properties (Thesis, Doctor of Philosophy). University of Otago. Retrieved from http://hdl.handle.net/10523/5974.
• Mehta P., Claydon L. S., Hendrick P., Cook C., & Baxter G. D. (2016). Pain and physical functioning in neuropathic pain: A systematic review of psychometric properties of various outcome measures. Pain Practice, 16(4), 495-508. doi: 10.1111/papr.12293.
• Mehta P., Claydon L. S., Hendrick P., Cook C., & Baxter G. D. (2018) Chronic Diabetic Peripheral Neuropathic Pain: Psychometric properties of pain and physical function outcome measures. Physical Therapy Reviews, doi.org/10.1080/10833196.2018.1517072.