Background & Aims

People with diabetes mellitus (DM) often develop diabetic peripheral neuropathy (DPN) which can be painful (DPNP).(1) DPNP in the feet or legs is associated with impairments of basic daily functioning, such as walking, concentrating, or sleeping, that result in impacts on well-being and quality of life.(2) The Neuropathy Total Symptom Score-6 (NTSS-6)(3,4) was developed and validated to briefly assess the frequency and severity of six neuropathic sensory symptoms: numbness; prickling; burning; aching; sharp, shooting pain; and allodynia or hyperalgesia in people with DM or DPN. The measure uses 4-point response scales, resulting in possible scores of 0-21 where a higher score indicates more frequent/severe symptoms. Clinician-reported and self-administered (NTSS-6-SA)4 versions are available with a 24-hour and a 4-week recall period, respectively. This observational study aimed to evaluate the NTSS-6-SA modified for use with a 7-day recall period in a sample of people with DPNP.

Methods

Two waves of individual semi-structured hybrid concept elicitation and cognitive debriefing interviews were conducted virtually with a diverse group of 24 US-based, English-speaking adults with a physician-confirmed diagnosis of DPN who self-reported having moderate to severe pain in the feet or legs. Interviewers asked participants to describe their experiences with DPNP and to read, respond to, and comment on the NTSS-6-SA with a 7-day recall period. Analysis included evaluating participant comprehension and interpretation of instructions, questions, and responses and documenting the relevance of each measured concept to participants’ experiences. Based on findings from the initial wave of 13 interviews, modifications were made to the instructions and to item phrasing to address problems with comprehension and incorporate patient feedback on the measure. The modified NTSS-6-SA (mNTSS-6-SA) was then reviewed in a further 11 interviews.

Results

Interview results indicated that all participants found the NTSS-6-SA relevant to their experiences and had little or no difficulty recalling or rating their experiences over a 7-day period. The concepts reflected in the measure items aligned with DPNP experiences spontaneously reported by participants during concept elicitation. However, participants in the first wave of interviews suggested that the lengthy original instructions developed for clinicians were unnecessary for people with DPNP and there were some identifiable sources of misreading or confusion in the phrasing of items. Modifications to address participant input included reducing the length of instructions and improving the phrasing of items as suggested. Participants completing interviews with the mNTSS-6-SA reported no further challenges with comprehension and did not identify the need for further improvements to the measure.

Conclusions

The mNTSS-6-SA assesses relevant experiences that participants found important for understanding DPNP and evaluating treatment. The item language aligns with terms spontaneously used by participants during concept elicitation. Participants found the modified instructions and items clear and easy to understand, and could recall and rate their experiences over a 7-day period using the available response options. Reducing the instructions did not affect participant understanding of the instrument or their ability to respond to items, nor did it contribute to any noticeable differences in the way responses were selected. Participants did not perceive the measure as missing any important content. The overall results indicate that the mNTSS-6-SA is well-understood and interpreted as intended, and includes content relevant to the assessment of changes in DPNP experiences that result from treatment. These results demonstrate that the measure exhibits content validity for people with DPNP.

References

1. Jensen TS, Karlsson P, Gylfadottir SS, Andersen ST, Bennett DL, Tankisi H, et al. (2021). Painful and non-painful diabetic neuropathy, diagnostic challenges and implications for future management. Brain. 2021;144:1632–45.
2. Kanera IM., van Laake-Geelen CCM, Ruijgrok JM, Goossens M, de Jong JR, Verbunt JA et al. (2019). Living with painful diabetic neuropathy: insights from focus groups into fears and coping strategies. Psychol Health. 2019;34(1):84-105.
3. Bastyr EJ, Price KL, Bril V, Group MS. Development and validity testing of the neuropathy total symptom score-6: questionnaire for the study of sensory symptoms of diabetic peripheral neuropathy. Clin Ther. 2005;27(8), 1278-1294.
4. Perrin NA, Nichols GA, Brown JB, Oglesby A, Bastyr EJ. The reliability and validity of a self-administered version of the neuropathy total symptom score-6 (NTSS-6-SA). Diabetologia. 2004;47:A35-A35.

Presenting Author

Virginia Stauffer

Poster Authors

Rikki Mangrum

MLS

Vector Psychometric Group, LLC

Lead Author

Ekin Seçinti

PhD

Eli Lilly and Company

Lead Author

Laure Delbecque

PhD

Eli Lilly and Company

Lead Author

Heather Gerould

MS

Vector Psychometric Group, LLC

Lead Author

Karolina Schantz

MPH

Vector Psychometric Group, LLC

Lead Author

Alexanda L. Bryant

BS

Vector Psychometric Group, LLC

Lead Author

Rebecca L. Robinson

MS

Eli Lilly and Company

Lead Author

Benjamin Behrend

PharmD

Eli Lilly and Company

Lead Author

Virginia Stauffer

Eli Lilly and Company

Lead Author

Topics

  • Specific Pain Conditions/Pain in Specific Populations: Neuropathic Pain - Peripheral