
==== Front
Interv Pain Med
Interv Pain Med
Interventional Pain Medicine
2772-5944
Elsevier

S2772-5944(22)00078-4
10.1016/j.inpm.2022.100087
100087
Original Article
An assessment of the validity and responsiveness of the Numerical Rating Scale version of the Pain Disability Quality-Of-Life Questionnaire-Spine
Burnham Robert rburnham@capriclinic.ca
abc∗
Amatto Lindsay d
Smith Ashley ce
Burnham Taylor f
Amatto Alycia a
a Division of Physical Medicine and Rehabilitation, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
b Central Alberta Pain and Rehabilitation Institute, Lacombe, Alberta, Canada
c Vivo Cura Health, Calgary, Alberta, Canada
d Faculty of Medicine and Dentistry, MD Program, University of Alberta, Edmonton, Alberta, Canada
e Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
f University of Utah, Department of Physical Medicine and Rehabilitation, Salt Lake City, UT, USA
∗ Corresponding author. Central Alberta Pain and Rehabilitation Institute, 1, 6220-Hwy 2A, Lacombe, T4L 2G5, Alberta, Canada. rburnham@capriclinic.ca
25 3 2022
6 2022
25 3 2022
1 2 10008717 1 2022
26 2 2022
7 3 2022
© 2022 The Authors
2022
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
The Numerical Rating Scale Version of the Pain Disability Quality-Of-Life Questionnaire-Spine (NRS PDQQ-S) is a six question compensate patient reported outcome measure designed for use in the field of minimally invasive interventional spine care. Although acceptable reliability, validity and responsiveness have been confirmed for the Visual Analog Scale version of the PDQQ-S in patients undergoing lumbosacral spine corticosteroid injections and radiofrequency neurotomy, the Numerical Rating Scale version has undergone limited psychometric assessment. The purposes of this study were to define the validity and responsiveness of the NRS PDQQ-S, and to do so in a cohort undergoing an emerging type of spine intervention (platelet rich plasma [PRP] injection). Prospectively gathered pre-and 6months post lumbosacral spine PRP injection(s) NRS PDQQ-S and Oswestry Disability Index (ODI) data were analyzed on 75 patients. NRS PDQQ-S construct validity was evaluated by calculating the correlation with the ODI. Internal responsiveness was estimated for both PDQQ-S and ODI by calculating the effect size (Cohen’s d). External responsiveness was estimated by calculating the correlation between the change scores of the NRS PDQQ-S and ODI. Strong statistically significant correlations were documented between the PDQQ-S and ODI questionnaires at pre-PRP injection (r ​= ​0.67; p<.0001) and 6 months post-PRP injection (r ​= ​0.82; p<.0001) supporting construct validity. Internal responsiveness was confirmed by large and comparable effect sizes for both the NRS PDQQ-S [1.1 (CI 0.8–1.4)] (1.1) and ODI [0.9 (CI 0.7–1.2)]. External responsiveness was confirmed by the strong correlation between the change scores of the NRS PDQQ-S and ODI [r ​= ​0.73 (p<.0001)]. This study supports the premise that the NRS PDQQ-S is a valid and responsive instrument that can be used to assess patients with low back pain who are treated with PRP injections.

Highlights

• The Pain Disability Quality-of-Life Questionnaire-Spine was designed for use in minimally invasive spine interventions.

• The original version scored question responses using the Visual Analog Scale and demonstrate good psychometric properties.

• A Numerical Rating Scale Version of the Pain Disability Quality-of-Life Questionnaire-Spine (NRS PDQQ-S) was developed.

• The NRS PDQQ-S demonstrated good validity and responsiveness in a cohort of low back pain sufferers receiving PRP injections.

Keywords

PDQQ-S
Validity
Responsiveness
==== Body
pmc1 Introduction

The Pain Disability Quality-Of-Life Questionnaire-Spine (PDQQ-S) is a short, six-question composite questionnaire that explores three domains of the pain experience - pain quality, disability, and life satisfaction/quality. The six questions are based on the patients’ average experience for the prior week and include: How severe has your pain been? (0 ​= ​no pain; 10 ​= ​worst possible pain); How often has your pain been present? (0 ​= ​never present, 10 ​= ​always present); For patient selected activity #1 How difficult is it for you to do the activity? (0 ​= ​no difficulty, 10 ​= ​completely unable to do it); For patient selected activity #2 - How difficult is it for you to do the activity? (0 ​= ​no difficulty, 10 ​= ​completely unable to do it); If you had to live with the pain you have now for the rest of your life, how satisfied would you be? (0 ​= ​completely satisfied, 10 ​= ​completely unsatisfied); How much has your pain disrupted the quality of your life? (0 ​= ​not at all, 10 ​= ​completely ruined it). The NRS PDQQ-S is scored from 0 (meaning no pain, disability, and life satisfaction/quality disruption) to 60 (maximal pain, disability, and life satisfaction/quality disruption). It was designed as an efficient and easy-to-use patient reported outcome measure (PROM) for minimally invasive spine interventions. The initial version quantified responses using a Visual Analogue Scale (VAS PDQQ-S). Psychometric evaluation confirmed its ease of use, reproducibility, validity, and responsiveness as a PROM for lumbosacral corticosteroid injections and radiofrequency neurotomy (RFN) [1]. The questionnaire was subsequently modified to a 0–10 Numerical Rating Scale format (NRS PDQQ-S) to facilitate electronic and over the telephone completion. More recently, the NRS PDQQ-S has been used as a PROM to document the effects of spine platelet rich plasma (PRP) injections. To date, psychometric evaluation of the NRS PDQQ-S version has been limited to defining the Minimal Clinically Important Difference (MCID). This was demonstrated to be a17-point score reduction. [submitted to Interventional Pain Medicine manuscript INPM-D-21-00026].

Although quantification of pain using VAS and NRS yield similar results, each format has advantages and disadvantages, and using their scores interchangeably may be problematic [2,3]. The NRS has been preferred by patients and some medical professionals due to its efficiency, and lack of need for additional tools or a patient’s motor skills for completion. However, it may be impacted by language barriers [2,4,5]. Certain populations, such as elderly individuals, those with visual, physical, or cognitive impairment, and of lower education have been found to have higher degrees of difficulty with the VAS [2,3]. The VAS cannot be completed over the phone, and the scale proportions may be altered through photocopy [6]. When directly converting scores between NRS and VAS, NRS scores were shown in one study to be slightly higher, hypothesized to be related to differences in score increments [5].

The purposes of this brief report are to describe the validity and responsiveness of the NRS PDQQ-S and to do so in a cohort undergoing an emerging minimally invasive spine intervention treatment (PRP injection) it has not been used for previously.

2 Materials and methods

Data were extracted from a prospectively gathered PROM registry of patients receiving PRP injections to treat low back pain at the same rural multidisciplinary chronic musculoskeletal pain management clinic (Central Alberta Pain and Rehabilitation Institute, Lacombe, Alberta, Canada). The cohort included 75 patients with a mean (sd) age of 59.9 (13.8) years. The extracted data included NRS PDQQ-S and Oswestry Disability Index (ODI) questionnaires completed at pre-and six months post PRP injections of the lumbosacral spine targeting one of, or combinations of joints (facet, sacroiliac), epidural space (caudal or interlaminar) and/or discs (intradiscal). The registry data protocol was approved by the Conjoint Health Research Ethics Board at the University of Calgary (Ethics ID#: REB20-0355). Prior psychometric testing of the ODI has confirmed excellent validity and acceptable reliability for use with patients undergoing treatment for low back pain [7,8].

3 Theory/calculation

Response to the PRP injections was explored using one-way repeated measures ANOVA analysis for NRS pain, NRS PDQQ-S and ODI. Construct validity was explored by assessing the correlation between the PDQQ-S and ODI pre-intervention and 6 months post-intervention scores using Pearson Correlation Coefficient. Internal responsiveness was estimated for both PDQQ-S and ODI by calculating the effect size using the pooled standard deviation method (Cohen’s d). External responsiveness was estimated by calculating the correlation between the change scores of the NRS PDQQ-S and ODI [9].

4 Results

Significant improvements in pain and disability following PRP injection were documented. Specifically, the pre:post-treatment scores(sd), F-value and P-value were: NRS pain pre 6.6(2.1):post 4.3(2.6), F ​= ​47.5, P <.001; PDQQ-S pre 43.8(9.5):post 29.5(15.9), F ​= ​65.2, P <.001; ODI pre 44.6 (13.3):post 30.4 (16.9), F ​= ​63.8, P <.001. The results of the psychometric analyses of the NRS PDQQ-S PRP are summarized in Table 1.Table 1 The validity and responsiveness of the numerical rating scale version of the pain disability quality-of-life-questionnaire-spine.

Table 1VALIDITY	NRS PDQQ-S: ODI correlation	
Pre-Platelet Rich Plasma Injection	r ​= ​0.67 (p<.0001)	
6 months post-Platelet Rich Plasma Injection	r ​= ​0.82 (p<.0001)	
		
	NRS PDQQ-S (CI)	ODI (CI)	
INTERNAL RESPONSIVENESS	1.1 (0.8–1.4)	0.9 (0.7–1.2)	
			
EXTERNAL RESPONSIVENESS	NRS PDQQ-S: ODI change score correlation	
	r ​= ​0.73 (p<.0001)	
Abbreviations: NRS PDQQ-S = Numerical Rating Scale version of the Pain Disability Quality-Of-Life Questionnaire-Spine; ODI = Oswestry Disability Index; CI ​= ​95% confidence interval.

5 Discussion

A valid PROM is one that measures what it is intended to measure. One method of assessing validity of a PROM (NRS PDQQ-S) is to evaluate the strength of its correlation with a validated PROM that measures the same or similar construct (ODI). The NRS PDQQ-S demonstrated validity based on significant and strong correlations with the ODI at both the pre-PRP (r ​= ​0.67) and 6months post-PRP (r ​= ​0.82) time periods. The responsiveness of a PROM relates to its ability to measure change. Internal responsiveness characterizes the ability of a measure to change over a pre-specified timeframe (i.e., before and 6 months post-PRP). The ability of both the NRS PDQQ-S and ODI to detect post-treatment change were significant, strong, and comparable (NRS PDQQ-S 1.1; ODI 0.9). External responsiveness reflects the extent to which changes in a PROM (NRS PDQQ-S) over a specified timeframe relate to corresponding changes in a reference PROM (ODI). The significant and strong correlation confirms external responsiveness (r ​= ​0.73).

These values compare favorably to previously documented psychometric evaluation of the VAS version of the PDQQ-S [1]. In that study, the validity assessment evaluated the 3 domains of the questionnaire (pain, disability, quality-of-life) separately. The sum of the 2 disability questions of the VAS PDQQ-S were correlated with the ODI pre-and post treatment and was found to be strong (r ​= ​0.71). We recently reanalyzed the raw data from that study to make them comparable to the current study. The correlation between the total VAS PDQQ-S score and ODI was r ​= ​0.51 (p ​= ​.0003) at pre-treatment and r ​= ​0.67 (p ​= ​.0002) at post-treatment. These correlations are slightly weaker than those documented with the NRS PDQQ-S. Internal responsiveness for the VAS PDQQ-S study had originally been assessed using a different metric (Responsiveness Ratio). The responsiveness was recalculated using the raw data of the VAS PDQQ-S study using the effect size method as was employed in the current study. VAS PDQQ-S responsiveness (effect size) was 1.5 whereas ODI responsiveness was 0.9. These are both large effect sizes indicating good responsiveness. Comparatively, the VAS PDQQ-S effect size is slightly greater than the NRS PDQQ-S whereas the ODI effect size was identical in both studies. Overall, the validity and responsiveness of both the VAS PDQQ-S and NRS PDQQ-S are strong and comparable. These, in addition to the recently described MCID, indicate a favorable psychometric profile of the NRS PDQQ-S.

We found both the NRS PDQQ-S and ODI to be significantly and comparably responsive. It would be reasonable to question why a clinician or researcher would choose the NRS PDQQ-S over the ODI. There may be a few possible advantages. Based on our previous research exploring the psychometrics of the VAS PDQQ-S [1], it’s likely that the NRS-PDQQ S is quicker to complete and easier to understand than the ODI. Additionally, the NRS PDQQ-S explores three domains of the pain experience in a balanced way (two questions for each of pain, disability and quality-of-life) compared to the ODI which explores two dimensions of the pain experience in an unbalanced way (two questions relating to pain; eight relating to disability). Lastly, the PDQQ-S allows the patient to self select the two disabilities they are rating whereas the ODI has only pre-set questions.

The authors acknowledge that it would be more customary to evaluate the psychometrics of a new PROM based on its performance in relation to an established intervention. Since PRP injection for mechanical low back pain is a relatively new and minimally investigated intervention. it may be considered a limitation to this study. However, we opine there is value to the current study because: a) regenerative medicine has been identified as a research priority for interventional musculoskeletal pain management and therefore PROMs with strong psychometric properties for regenerative therapies need to be identified, b) we used both a new PROM (NRS PDQQ-S) as well as a commonly used, psychometrically established PROM (ODI) in our analysis, c) although a new intervention, there was a significant treatment effect allowing the mathematical calculation of the validity and responsiveness of the PROM which was the primary purpose of the study, and d) it is common to establish psychometric properties of PROM for multiple clinical applications.

The study helps to establish the properties of the NRS PDQQ-S as they apply to PRP injections to treat mechanical low back pain. Future research should include evaluating its psychometrics for other interventional spine procedures such as facet joint radiofrequency neurotomy, basivertebral nerve ablation, epidural steroid injections etc.

6 Conclusion

The NRS PDQQ-S demonstrated good validity and responsiveness. This supports it's use as a PROM in the realm of injection therapy for mechanical low back pain particularly using PRP.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

Christie Lewis for her assistance with outcome data collection.
==== Refs
References

1 Burnham R. Stanford G. Gray L. An assessment of a short composite questionnaire designed for use in an interventional spine pain management setting Pharm Manag PM R 4 6 2012 413 418 10.1016/j.pmrj.2012.03.018
2 Govas P. Ketchum A. Kazi R. Gordon B.R. Carroll B.T. Pain intensity assessment scales for dermatologic surgery patients: a systematic review [published online ahead of print, 2021 dec 14] Dermatol Surg 2021 10.1097/DSS.0000000000003353
3 Hjermstad M.J. Fayers P.M. Haugen D.F. Studies comparing numerical rating scales, verbal rating scales, and visual Analogue scales for assessment of pain intensity in adults: a systematic literature review J Pain Symptom Manag 41 6 2011 1073 1093 10.1016/j.jpainsymman.2010.08.016
4 Shafshak T.S. Elnemr R. The visual Analogue scale versus numerical rating scale in measuring pain severity and predicting disability in low back pain J Clin Rheumatol 27 7 2021 282 285 10.1097/RHU.0000000000001320 31985722
5 Mohan H. Ryan J. Whelan B. Wakai A. The end of the line? The Visual Analogue Scale and Verbal Numerical Rating Scale as pain assessment tools in the emergency department Emerg Med J 27 5 2010 372 375 10.1136/emj.2007.048611 20442167
6 Akad K. Solmaz D. Sari I. Onen F. Akkoc N. Akar S. Performance of response scales of activity and functional measures of ankylosing spondylitis: numerical rating scale versus visual analog scale Rheumatol Int 33 10 2013 2617 2623 10.1007/s00296-013-2789-x 23736275
7 Saltychev M. Mattie R. McCormick Z. Bärlund E. Laimi K. Psychometric properties of the Oswestry disability Index Int J Rehabil Res 40 3 2017 202 208 10.1097/MRR.0000000000000226 28368870
8 Vianin M. Psychometric properties and clinical usefulness of the Oswestry disability Index J Chiropr Med 7 4 2008 161 163 10.1016/j.jcm.2008.07.001 19646379
9 Husted J.A. Cook R.J. Farewell V.T. Gladman D.D. Methods for assessing responsiveness: a critical review and recommendations J Clin Epidemiol 53 5 2000 459 468 10.1016/s0895-4356(99)00206-1 10812317
