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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 37  |  Issue : 2  |  Page : 57-62

Reliability and validity of the Turkish version of king's Parkinson's disease pain scale


1 Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Nuh Naci Yazgan University, Kayseri, Turkey
2 Department of Neurology, Faculty of Medicine, Erciyes University, Kayseri, Turkey
3 Department of Biostatistics, Faculty of Medicine, İzmir Katip Çelebi University, Izmir, Turkey

Date of Submission16-Apr-2019
Date of Decision10-Sep-2019
Date of Acceptance17-Apr-2020
Date of Web Publication29-Jun-2020

Correspondence Address:
Ferhan Soyuer
Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Nuh Naci Yazgan University, Kayseri
Turkey
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/NSN.NSN_34_20

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  Abstract 


Objective: Pain, a nonmotor symptom in Parkinson's disease (PD), affects approximately 40%–85% of patients and adversely affects their daily activities. Therefore, our aim was to establish the validity and reliability of the Turkish version of King's PD Pain Scale (KPDPS) and to make it available for Turkish patients with PD patients. Methods: The first phase of the study involved the translation and adaptation of the KPDPS to Turkish. For the language validity of the scale, a translation back-translation method was applied, and expert's opinion was considered for content validity. In the second stage, the developed Turkish scale was administered to 152 patients with PD. In the study, test-retest was performed in 50 patients for 1 week. Results: The internal consistency value was found as 0.856 in the KPDPS. When the test-retest was performed, the internal consistency value of the scale showed excellent reliability. The test-retest-Cronbach's alpha value for the whole scale was 0.827. According to the data analysis results, it showed that 14 items on the scale were sufficient for the evaluation of pain in patients with PD. Conclusion: The results from this study show that KPDPS items have adequate internal consistency and test-retest reliability. The Turkish KPDPS can be used as a reliable and valid instrument for assessing the pain symptoms common to patients with PD.

Keywords: Pain assessment, pain scale, Parkinson's disease, reliability, validation study


How to cite this article:
Soyuer F, Gültekin M, Cankurtaran F, Elmalı F. Reliability and validity of the Turkish version of king's Parkinson's disease pain scale. Neurol Sci Neurophysiol 2020;37:57-62

How to cite this URL:
Soyuer F, Gültekin M, Cankurtaran F, Elmalı F. Reliability and validity of the Turkish version of king's Parkinson's disease pain scale. Neurol Sci Neurophysiol [serial online] 2020 [cited 2020 Oct 20];37:57-62. Available from: http://www.nsnjournal.org/text.asp?2020/37/2/57/288419




  Introduction Top


Pain causes clinical and socioeconomic burdens and is one of the reasons for disability that significantly affects the quality of life of patients and their families.[1],[2] Several pain taxonomies have been described in the medical literature. The International Association for the Study of Pain Subcommittee on Taxonomy defines pain as “an unpleasant sensory and emotional experience associated with potential tissue damage or actual or described in terms of such damage,” whereby other domains such as cognition and emotion are implicated in maintenance, origin of pain, and its management.[3],[4]

Pain represents one of the most common nonmotor symptoms that affects people with Parkinson's disease (PD). It was first described in 1817 by James Parkinson in his work, “An Essay on Shaking Palsy,” and has been recently reviewed because it represents a common symptom that leads to disability and reduces the quality of life.[5],[6] The prevalence of pain ranges from 40% to 85%.[7],[8] Musculoskeletal pain is the most common (up to 58.5%), followed by radicular peripheral neuropathic (38%), dystonic (33.5%), and central neuropathic pain (8.5%). Chronic pain affects 61.8% of patients with PD. Nearly 60.1% of pain syndromes are associated with PD, the remainder are from other origins (such as osteoarthritis, unrelated to PD).[9],[10],[11]

Until recently, no standardized assessment protocols had been developed to evaluate the pain in PD. Most pain-identifying data in PD were obtained using non-disease-specific tools to assess pain, such as the McGill Pain Scale, the 36-item Short Form Health Survey, and the Brief Pain Inventory. Recently, the King PD Pain Scale (KPDPS) was developed and approved in 178 patients with PD and 83 age- and sex-matched controls showing higher KPDPS total scores most often in the musculoskeletal system pain, chronic pain, fluctuation-related pain, nocturnal pain, orofacial pain, and radicular pain.[12]

In our country, there is no valid and reliable measuring instrument that can be used to assess pain specific to PD. For this reason, this research was conducted to determine the validity and reliability of the Turkish version of the KPDPS, which was developed to evaluate the pain occurring in patients with PD.


  Methods Top


Studies on language validity of King Parkinson's Disease Pain Scale

For the validity and reliability study of the scale, permission was obtained from the authors through e-mail. In order to test the validity of the KPDPS for Turkish cultural adaptation, studies were conducted on the validity of the scale at the first stage of the research.[13] In this process, two individuals who were blinded, one neurologist and one English language and literature graduate, performed the linguistic validity and reliability study in Turkish in line with the culture of Turkish society in accordance with the rules of forward translation. A common decision was made in the forward translation, and the scale was finalized. In the following stage, the Turkish version was translated back into English by a fluent English speaker. It was found that there was no difference between the original and the translated back-translated scale.

After the required regulations were made, the Turkish scale was presented expert opinion in terms of content validity. The expressions made understandable according to the recommendations were used for the preliminary application.

Statistically, it is recommended to apply a sampling of ten times the number of items of a scale translated into Turkish.[13] In this respect, this number was determined as 140 (10 × 14 = 140) for the scale used in our study.

After the study was completed, the scale was administered to 50 patients for 7–15 days for test-retest. Between the test-retest, there was no treatment for pain symptoms.

Participants who were considered for the study were given volunteer proclamation forms indicating the purpose and content of the research individuals who gave verbal approval were included in the study. Approval for the study was obtained from Erciyes University Ethics Committee for Clinical Investigations (Date: 04.12.2016, No: 2016/527).

Sampling

This study was conducted between February 2016 and March 2018, at the Erciyes University Medical Faculty Neurology Clinic. A total of 152 patients with aged 40–90 years, without any diseases that could cause PD independently, who could communicate, were in the “on” period, and who had had pain for at least 3 months, were enrolled in the study. Sixty-one patients were female and 91 were male.

Patients with hearing and speech problems, those with any current major psychopathology diagnosis according to the Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition diagnostic criteria and under psychiatric-psychological treatment, any neurologic disease other than PD, and those receiving medical treatment for pain symptoms were excluded from the study.

Data collection tools used

The staging of the disease was performed using the Hoehn-Yahr (H and Y) Scale, the Unified PD Assessment Scale for the clinical severity, and the Standardized Mini Mental State Examination for the assessment of the cognitive status of the patients. A Visual Analog Scale (VAS) was used to test the validity of the structure concept of the KPDPS.

Hoehn-Yahr Scale

The scale used for staging PD was developed by H and Y in 1967. Stages are defined as 1, 1.5, 2, 2.5, 3, 4, and 5.[14]

Unified Parkinson's Disease Rating Scale

The UPDRS evaluates mental and psychological state, activities of daily living, motor performance, and treatment complications in PD. The highest score that can be achieved in the UPDRS is 183.[15],[16]

Standardized Mini Mental Test

This is a standardized test that is widely used to evaluate cognitive performance. The time, space orientation, recording memory, attention, memory, and language items consist of five subsections. The lowest possible score from the test is 0, the highest score is 30.[17],[18]

Visual Analog Scale

In this study, a visual scale was used to determine the severity of pain. This scale is 100 mm long. There is a “0” on one end of the scale and a “10” on the other end. 0 means “no pain,” 10 means “the most severe pain.” People with chronic pain are asked to indicate the point that best describes how severe their pain is on this scale.[19]

Parkinson's Disease Pain Scale

The KPDPS is a scoring-based scale that evaluates pain by interviewing patients with PD.[12] It consists of 14 items divided into seven different domains. Each item is scored by multiplying the severity (0 [no pain]-3 [very severe pain]) (0 [never]-4 [always]), which gives subscores ranging from 0 to 12, with a sum returns the total score between 0 and 168. The domains and score ranges are as follows: (1) musculoskeletal pain (range: 0 and 12); (2) chronic pain (range: 0 and 24); (3) pain associated with fluctuation (range: 0 and 36); (4) night pain (range: 0 and 24); (5) orofacial pain (range: 0 and 36); (6) discoloration, edema/swelling (range 0 and 24); and (7) radicular pain (range, 0 and 12).[12]

Statistical analysis

The data were evaluated using the Statistical Package for the Social Sciences program version 22.0 (IBM Corp., Armonk, New York, USA). The descriptive statistics were as follows: unit number (n), percent (%), mean ± standard deviation, and median ( first quarter to third quarter). The normality of distributions of the numerical variables was evaluated using to Shapiro-Wilk normality test and Q-Q graphs. For internal consistency between the items, Cronbach's alpha coefficient was used. Tukey's additive test was used for the additive. The Kaiser–Meyer-Olkin test was used for the adequacy of the sample number, and the Bartlett test was used to evaluate the factor structure. The Varimax method was used as the factor rotation method. Scale reliability was evaluated by test-retest, intraclass correlation coefficients, and the Wilcoxon test in matched samples. Statistical significance was evaluated at the level of P < 0.05.


  Results Top


The sample of the study consisted of 152 patients (61 females and 91 males). The sociodemographic characteristics of the patients are given in [Table 1], and their clinical findings are presented in [Table 2].
Table 1: Sociodemographic characteristics of the patients with Parkinson's disease

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Table 2: Clinical findings and correlations of patients with Parkinson's disease

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Construct validity

The correlation coefficients between the KPDPS and the other clinical assessments are summarized in [Table 2]. Positive correlations were found between the KPDPS score and other clinical assessments (P < 0.05), except for the mini-mental test score.

Validity analysis

The internal consistency value of 14 items for the KPDPS was found as 0.856. The total correlations of items corrected according to [Table 3] were found to be over 0.3. In addition, 14 items were collectable (F = 27. 119; P < 0.001). Kaiser-Meier-Olkin sample adequacy value was 0.780, and the Bartlett sphericity test was statistically significant (χ2 = 1048; P < 0.001). According to these results, all items could be evaluated by the factor analysis. Convergent validity showed a significant correlation between the total score of KPDPS and VAS (r = 0.724 P < 0.001).
Table 3: Item statistics (frequency and severity)

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Reliability analysis

Test-retest correlations and Cronbach alpha values were calculated to test the reliability of the scale. When the test-retest was performed, the Cronbach's alpha coefficient for the whole scale was 0.827. According to [Table 4], between the two measurements, there was a moderate and good agreement, and there was no difference between the measurements. In the end, the scale was found to be reliable.
Table 4: Differences between correlation coefficients and measurements between the first test and test-repeat test

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  Discussion Top


We aimed to demonstrate that the Turkish version of the KPDP was valid, reliable, and useful in our study, due to the fact that there is no scale or scale with validity and reliability in Turkish patients evaluating pain alone in PD.

It is very important to investigate the understandability and responsiveness of a scale to the target population. If the scale is prepared on another level, some essential steps need to be taken. When the scale is translated into another language, it makes it easier to understand how to make the adaptation considering the sociocultural characteristics of the target community. For this reason, the English version of the KPDPS went through a translation process, and a Turkish version was created.

The scale developed by Chaudhuri et al.[12] to evaluate the pain in patients with PD is composed of seven items. Psychometric evaluations were made after the language validity was achieved in our study. In addition, factor analysis was performed to examine the construct validity and to determine whether the items were adequately represented in the subscales and to explain the specific structure of the scale.

For the reliability analysis of the scale, item-down correlation, Cronbach's alpha test (internal consistency) and test-retest (time invariance) were used. A statistically significant relationship is expected between the item-subscale correlations and the contribution of each item to the subscale and the contribution of each subscale to the total scale. Although the lower limit of this coefficient has different values in the literature, 0.20 is generally considered to be the lowest level, and items with a correlation coefficient of 0.30–0.40 and >0.40 show “good” and “very good” discrimination, respectively, and therefore reliable.[13] In view of these, the item-subscale correlations in the Turkish version of the KPDPS were found to have a range of 0.31–0.62, respectively, and no item required exclusion from the scale.

The management of pain in PD is complicated by the lack of a standardized tool, taking into account as much difference as possible between the various types of pain, as well as the distinction of pain, because there is no standardized tool for the global assessment of pain in PD, pain secondary to the pathogenic process of PD, and comorbidities of PD.[4],[11]

The data from the seven domains of the KPDPS provide information on the different types of pain that are distinguished by extensive nociceptive and neuropathic patterns in PD. Despite its complex structure, our study showed that the scale is a valid and reliable measurement tool in Turkish. The internal consistency value of the 14 items for the KPDPS was found as 0.856. This result shows that the scale is consistent in itself and the homogeneity of the scale is high. In the original version, this value was 0.70 or higher.[12]

Test-retest reliability analysis was performed with 50 cases. Pearson correlation coefficient was used for the reliability analysis. The correlation level was found to be high for the items of the evaluation scale. According to the test-retest results, there was moderate and good agreement between the two measurements. There was no difference between the measurements, meaning that. Our scale is reliable. This finding suggests that the scale produces steady results in measurements made at different times, in other words, it is reliable. On the original scale, the test was retested in 49 patients and values of 0.70 were determined.[12] These results prove that the Turkish version of KPDPS is a reliable scale that can be applied to patients with PD.

In our study, convergent validity showed a statistically significant correlation between total pain scores and VAS (r = 0. 724, P < 0.001). In the original KPDPS scores, there was a close correlation with the VAS score.[12] Weak and moderate correlations were found between pain measures and the King's PD Pain Questionnaire (KPDPQ).[20] However, it is important that the KPDPQ is only a screening tool, whereas the KPDPS is a quantitative measure of pain severity and frequency in PD.

There are some limitations of this study. The patient's charateristics should be taken into consideration when interpreting the results, such as the outpatient treatment of the patients, the length of follow-up of the symptoms, and the evaluation in a polyclinic. An important limitation of KPDPS is that it was based on the subjective feelings and perceptions to measure the patient's pain. We had to exclude patient with clinical dementia because the assessment of the subjective aspects of pain would be unreliable and/or impossible.

The findings from this study show that the KPDPS has adequate internal consistency and test-retest reliability. In conclusion, the Turkish version of KPDPS was determined to be a valid and reliable scale that could be used for evaluating pain in patients with PD.

A practical assessment of pain experienced by the patient with PD using the KPDPS can be useful in clinical practice. In future prospective patient studies, we recommend the use of this form and testing the sensitivity of the form to determine the changes in the clinical symptoms of patients with PD.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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