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Neck disability index, Visual analog scale, and Likert scale in patients receiving pharmacotherapy for neck pain: How good do they correlate?


Many validated tools are available to assess the effectiveness of treatment for neck pain. These patient oriented instruments for outcome measurement include numeric scales, validated disease-specific functional outcomes measures, and quality of life outcome measures. However, it is not clear whether all these patient reported outcomes are measuring different entities and whether all these should be measured after pharmacotherapy of neck pain. [1]

The neck disability index (NDI) is a commonly used, simple and validated outcome measurement tool, which is available in multiple languages to determine self-assessed disability in patients with neck pain. Many studies published so far had used NDI as an effective tool in assessing the difference in pre- and post-treatment condition of the patients. [2,3] The NDI consists of different functional items related to neck pathologies and it gives a visual template for collection of information. [4] It is a 10-item questionnaire that measures a patient's self-reported neck pain related disability. Questions include activities of daily living, such as: Personal care, lifting, reading, work, driving, sleeping, recreational activities, pain intensity, concentration, and headache. Each question is measured on a scale from 0 (no disability) to 5, and an overall score out of 100 is calculated by adding each item score together and multiplying it by two. A higher NDI score means the greater a patient's perceived disability due to neck pain. [5,6]

Visual analog scale (VAS) is another frequently used tool in clinical practice as an outcome measure. How VAS relates with neck pain and patient's self-reported disability still needs to be investigated. VAS is usually a horizontal line, 10 cm in length, anchored by word descriptors at each end like 0 represents no pain, 10 represent maximum pain. The patient was asked to mark on the line, the point that he/she feel represents the pain perception at that time. The VAS score was determined by measuring in centimeters from the left hand end of the line to the point marked by the patient. [7] In general, improvements of pain severity on a pain intensity numerical rating scale like VAS, may not be seen as improvement in disability. [8,9] The association between neck pain, the NDI, and VAS for pain was investigated in this study.


This was a prospective observational study conducted in the outpatient Department of Physical Medicine and Rehabilitation, in a Tertiary Care Hospital. Patients who were willing to participate in the comparative study of thiocolchicoside and tolperisone [7] were included. Pregnant and lactating women, those with history of epilepsy, and those with cognitive deficit were excluded from the study.

Study comprehended two patient visits: An initial visit and one follow-up visit after two weeks. In the first visit, information regarding patient demographics, clinical diagnosis, and medications he/she were on, was obtained from the patient/care giver and then recorded on the pre-validated proforma. Tools selected for assessing the effectiveness of pharmacotherapy were: VAS, 5-item Likert scale, and NDI. Patient's pain status was determined using VAS for pain and they were also asked to qualify their clinical situation using a 5-item Likert scale varying from excellent to bad. The possible qualifications of their situation were: Excellent, very good, good, moderate, and bad. The disability level of the patient due to neck pain was found out using NDI questionnaire and score was noted. All patients were treated with a skeletal muscle relaxant and analgesics for a period of 2 weeks. Skeletal muscle relaxants used for the treatment were either thiocolchicoside 8 mg two times daily or tolperisone 150 mg two times daily. All patients also received any one of the following NSAIDs such as diclofenac, aceclofenac, ibuprofen, naproxen, or paracetamol. During the follow-up visit, pain status and disability level of the patient were assessed in a similar way as in the initial visit.

For statistical analysis SPSS version 20 (@IBM) was used. Continuous variables were depicted as mean [+ or -] standard deviation (minimum-maximum). For analyzing change in Likert scale after pharmacotherapy Wilcoxon signed ranks test was used. For analyzing change in NDI and VAS after pharmacotherapy paired t-test was used. The correlation of VAS and Likert scale for qualification of neck pain with NDI was estimated before and after pharmacotherapy using correlation coefficient.


A total of 170 patients attending physical medicine and rehabilitation department with neck pain were included in the study. The age range of patients included in the study was between 20 and 65 with a mean age of 47.41 [+ or -] 9.76 years. 126 (74.1%) patients included in the study were females and 44(25.9%) were males. The majority of patients (85.9%) were diagnosed to have cervical spondylosis.

Effectiveness of pharmacotherapy in neck pain was assessed using qualitative Likert scale, VAS, and NDI. Before treatment majority of patients (67.1%) rated their clinical condition as moderate and after treatment majority rated it as very good with the Likert scale. After treatment, there was a significant change in Likert scale, Z=11.03, P < 0.001 (Figure 1). 16.5% of patients opined their clinical condition as excellent after pharmacotherapy.

VAS score of patients showed a significant change after treatment (Table 1). Mean VAS score of patients before treatment was 7.82 [+ or -] 1.09 which was reduced by pharmacotherapy to 3.85 [+ or -] 1.78, which was statistically significant t = 28, P < 0.001, 95% confidence interval (3.7-4.25).
Figure 1: Distribution of patients in relation to qualitative Likert
scale rating

Number of patients
Likert Scale

           Before treatment   After treatment

Exellent           0              28
Very good          1              89
Good              15              34
Moderate         114              19
Bad               40               0

Note: Table made from bar graph.

NDI score of patients also was reduced by pharmacotherapy (Table 2). NDI mean score was 69.58 [+ or -] 13.32 before treatment which declined to 34.68 [+ or -] 16.04 which was significant. t = 28.199, P < 0.001, 95 % confidence interval (32.46-37.34).

The NDI score was correlated with Likert scale rating of patients (Figure 2). There was a positive correlation between NDI and Likert both before (r = 0.589, P < 0.01) and after (r = 0.776, P < 0.01) pharmacotherapy. Positive correlation increased after treatment. NDI and VAS score also showed positive correlation before (r = 0.663, P < 0.01) and after (r = 0.845, P < 0.01) pharmacotherapy. The correlation was strongly positive after treatment (Figure 3).


Currently, there are multiple tools to assess the effectiveness of pharmacotherapy. But most of the time the agreement between these tools in measuring effectiveness is unclear. The effectiveness of skeletal muscle relaxants can be determined by using tools which measure difference in pain status and also by tools which measure the improvement in disability caused by the disease itself. In our study qualitative Likert scale, VAS for pain and NDI were the tools used to assess the effectiveness of pharmacotherapy for neck pain. Several studies have used the same tools for assessing the effectiveness of pharmacotherapy and surgical treatment. [2-4]

There was a significant change in the Likert scale rating of patients following pharmacotherapy. The majority of patients rated their condition as very good after the treatment. Previous studies also proved qualitative Likert scale as an effective tool to measure the improvement in clinical condition after treatment. [10,11]

VAS showed significant reduction in scores following treatment with skeletal muscle relaxants and analgesics in the study population. In their study, Lee et al. measured the change in VAS score associated with adequate pain control and a mean reduction in VAS of 30.0 mm was observed which represented a clinically important difference in pain severity with respect to patients' perception of adequate pain control. [8,9]

In this study disability of patients due to neck pain was assessed using NDI before and after treatment and a significant reduction in scores was observed posttreatment which represented reduction in disability. This goes in agreement with the findings of study done by Donk et al. [10]

Our study also showed that there is a correlation between NDI and qualitative Likert scale rating which confirmed that improvement in pain status is also associated with reduced disability of patients with neck pain. Donk et al. compared the qualification of outcome by patients after cervical spine surgery to the NDI and found that there was a correlation between qualification of the situation by the patients themselves and NDI. In their study, an NDI-7 corresponded to a good outcome according to the patients. [10]

The correlation between NDI and VAS also was studied in this study which showed a positive correlation both before and after treatment. Strong positive correlation was observed after pharmacotherapy.

In their study, Cleland et al. observed that both the NDI and numeric rating scale for pain, exhibit fair to moderate test-retest reliability in patients with mechanical neck pain. Both instruments also showed adequate responsiveness in that patient population. [11]

In a similar study, En et al. evaluated the construct and content validity of the neck pain and disability scale (NPAD) along with NDI. The NDI and NPAD scores were strongly correlated (r = 0.86, P < 0.01), while the correlation between the problem elicitation technique and the fixed-item questionnaires was moderate (NDI: r = 0.62, P < 0.01; NPAD: r = 0.71, P < 0.01). Both the NDI and the NPAD include most of the functional problems common to this patient group, and display good content validity. [12] In another study done by Uthaikhup et al. [13] used the Thai versions of NDI and NPDS and concluded that the NDI-TH, NPDS-TH, and NPDS-TH subscales were moderately correlated with the VAS (range, r = 0.61-0.76, P < 0.001).


The effectiveness of pharmacotherapy in patients with neck pain was evaluated using qualitative Likert scale rating by the patient, VAS for pain and NDI. There was a significant change in Likert scale rating and significant reduction in mean VAS and mean NDI after pharmacotherapy. Study showed a positive correlation between the qualification of the clinical condition with Likert scale and NDI as well as between VAS for pain and NDI. Hence, NDI can be considered as an effective tool in evaluating the effectiveness of pharmacotherapy.


We extend our sincere gratitude to the Head of Department and other colleagues in the Department of Pharmacology and staff of the Department of Physical Medicine and Rehabilitation for their help and valuable suggestions. We are extremely grateful to the patients who agreed to be part of this study, without whose co-operation this study would have been impossible. We also thank Dr. Carol Pinheiro and Dr. Viswakala V S, Department of Social Preventive Medicine, Government TD Medical College for statistical suggestions.


[1.] DeVine J, Norvell DC, Ecker E, Fourney DR, Vaccaro A, Wang J, et al. Evaluating the correlation and responsiveness of patient-reported pain with function and quality-of-life outcomes after spine surgery. Spine (Phila Pa 1976). 2011;36 21 Suppl: S69-74.

[2.] MacDermid JC, Walton DM, Avery S, Blanchard A, Etruw E, McAlpine C, et al. Measurement properties of the neck disability index: A systematic review. J Orthop Sports Phys Ther. 2009;39(5):400-17.

[3.] Howell ER. The association between neck pain, the neck disability index and cervical ranges of motion: A narrative review. J Can Chiropr Assoc. 2011;55(3):211-21.

[4.] Goolkasian P, Wheeler AH. Re: Pietrobon R, Coeytaux RR, Carey TS, et al. Standard scales for measurement of functional outcome for cervical pain or dysfunction: A systematic review. Spine. 2002;27:515-22.

[5.] Vernon H, Mior S. The neck disability index: A study of reliability and validity. J Manipulative Physiol Ther. 1991;14(7):409-15.

[6.] Vernon H. The neck disability index: State-of-the-art, 1991-2008. J Manipulative Physiol Ther. 2008;31(7):491-502.

[7.] Joseph LR, Asha S, Menon S. Comparison of effectiveness and safety of thiocolchicoside and tolperisone in patients with cervicobrachialgia - A prospective observational study. Int J Pharmacol Ther. 2014;4(3):1-9.

[8.] Lee JS, Hobden E, Stiell IG, Wells GA. Clinically important change in the visual analog scale after adequate pain control. Acad Emerg Med. 2003;10(10):1128-30.

[9.] Kovacs FM, Abraira V, Royuela A, Corcoll J, Alegre L, Tomas M, et al. Minimum detectable and minimal clinically important changes for pain in patients with nonspecific neck pain. BMC Musculoskelet Disord. 2008;9:43.

[10.] Donk R, Verbeek A, Verhagen W, Groenewoud H, Hosman A, Bartels R, et al. The qualification of outcome after cervical spine surgery by patients compared to the neck disability index. PLoS One. 2016;11(8):e0161593.

[11.] Cleland JA, Childs JD, Whitman JM. Psychometric properties of the neck disability index and numeric pain rating scale in patients with mechanical neck pain. Arch Phys Med Rehabil. 2008;89(1):69-74.

[12.] En MC, Clair DA, Edmondston SJ. Validity of the neck disability index and neck pain and disability scale for measuring disability associated with chronic, non-traumatic neck pain. Man Ther. 2009;14(4):433-8.

[13.] Uthaikhup S, Paungmali A, Pirunsan U. Validation of Thai versions of the neck disability index and neck pain and disability scale in patients with neck pain. Spine (Phila Pa 1976). 2011;36(21):E1415-21.

Liya Roslin Joseph (1), Dhanya Sasidharan Palappallil (2)

(1) Department of Pharmacology, Pushpagiri Institute of Medical Sciences & Research Centre, Thiruvalla, Kerala, India, (2) Department of Pharmacology, Government T D Medical College, Alappuzha, Kerala, India

Correspondence to: Liya Roslin Joseph, E-mail:

Received: December 02, 2016; Accepted: December 16, 2016

DOI: 10.5455/njppp.2017.7.1233917122016
Table 1: Distribution of patients in relation to VAS scale

VAS             N=170 (%)
     Before treatment  After treatment

 1         0                 4 (2.4)
 2         0                37 (21.8)
 3         0                49 (28.8)
 4         1 (0.6)          30 (17.6)
 5         2 (1.2)          17 (10)
 6        13 (7.6)          14 (8.2)
 7        46 (27.1)         12 (7.1)
 8        68 (40)            7 (4.1)
 9        28 (16.5)          0
10        12 (7.1)           0

VAS: Visual analog scale

Table 2: Distribution of patients in relation to NDI score

NDI                N=170 (%)
        Before treatment  After treatment

  0-10        0                  1 (0.6)
 11-20        0                 36 (21.2)
 21-30        0                 50 (29.4)
 31-40        3 (1.8)           29 (17.1)
 41-50        8 (4.7)           24 (14.1)
 51-60       36 (21.2)          16 (9.4)
 61-70       45 (26.5)           9 (5.3)
 71-80       40 (23.5)           4 (2.4)
 81-90       24 (14.1)           1 (0.6)
91-100       14 (8.2)            0

NDI: Neck disability index
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Author:Joseph, Liya Roslin; Palappallil, Dhanya Sasidharan
Publication:National Journal of Physiology, Pharmacy and Pharmacology
Article Type:Clinical report
Date:Mar 1, 2017
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