Validation of the French Version of the Brief Pain Inventory in Canadian Veterans Suffering from Traumatic Stress

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1 720 Journal of Pain and Symptom Management Vol. 33 No. 6 June 2007 Original Article Validation of the French Version of the Brief Pain Inventory in Canadian Veterans Suffering from Traumatic Stress Joaquin Poundja, BA, Deniz Fikretoglu, PhD, Stéphane Guay, PhD, and Alain Brunet, PhD University of Montréal (J.P., S.G.); Ste. Anne s Center (J.P., D.F., S.G., A.B.), Veterans Affairs Canada; Douglas Hospital Research Center (J.P., D.F., A.B.); McGill University (D.F., A.B.); and Fernand-Seguin Research Center (S.G.), Montréal, Québec, Canada Abstract Although pain is a significant clinical problem in individuals suffering from post-traumatic stress disorder (PTSD), reliable and valid measures of pain for this population are lacking. The goal of this study was to validate the Brief Pain Inventory (BPI) in French-speaking veterans suffering from PTSD (n ¼ 130). We administered the BPI, as well as measures of PTSD, health status, quality of life, and social desirability, to veterans being assessed or treated for PTSD at a Veterans Affairs Canada clinic. The BPI showed strong internal consistency, as evidenced by Cronbach s alphas of 0.90 and 0.92 for the severity and interference subscales, respectively. Similar to previous findings, a two-factor structure (pain severity and pain interference) was found using an exploratory factor analysis. The two factors explained nearly 73% of the variance of the instrument. The BPI was also strongly correlated with health status and quality of life in the physical domain. In this veteran sample, nearly 87% of the veterans suffered from significant current pain. Veterans in our sample reported rates of pain severity that were similar to or higher than most of those reported by cancer patients and others with significant physical disability/illness. Overall, the French version of the BPI is a reliable, valid measure of pain in PTSD-suffering populations. Pain is a major issue in veterans with PTSD, and should be screened for with instruments such as the BPI. J Pain Symptom Manage 2007;33:720e726. Ó 2007 U.S. Cancer Pain Relief Committee. Published by Elsevier Inc. All rights reserved. Key Words Brief Pain Inventory, pain, PTSD, validation, prevalence, Canadians, veterans, psychological trauma, French This study was supported by an internal grant from Veterans Affairs Canada. Alain Brunet acknowledges a salary award from the Fonds de Recherche en Santé du Québec, and Joaquin Poundja and Deniz Fikretoglu acknowledge a fellowship award from the Canadian Institutes of Health Research, while working on this manuscript. Ó 2007 U.S. Cancer Pain Relief Committee Published by Elsevier Inc. All rights reserved. Address reprint requests to: Alain Brunet, PhD, Douglas Hospital Research Center, 6875 LaSalle Blvd., Montréal, Québec H4H 1R3, Canada. alain.brunet@mcgill.ca Accepted for publication: September 25, /07/$esee front matter doi: /j.jpainsymman

2 Vol. 33 No. 6 June 2007 BPI in Canadian Veterans Suffering from Traumatic Stress 721 Introduction Pain is a significant comorbid condition in patients suffering from post-traumatic stress disorder (PTSD), both in civilian 1e3 and veteran populations. 4,5 This comorbidity is particularly high in veterans suffering from PTSD; according to Beckham et al., 5 up to 80% of veterans with PTSD might suffer from chronic pain. To explain the high comorbidity of PTSD and pain, it has been proposed that PTSD and pain could be in a mutual maintenance relationship whereby pain can exacerbate or maintain PTSD symptoms, and PTSD can worsen or maintain pain, 6,7 possibly via depression. 8 Pain thus seems a major factor in veterans for whom PTSD is the primary diagnosis, and validated pain measures are needed for screening purposes in this population. One of the most recognized measures of pain, the Brief Pain Inventory (BPI), 9 covers many of the content areas included in the widely used McGill- Melzack Pain Questionnaire 10 while taking less time to fill out. 11,12 Because of its brevity, the BPI is particularly useful for screening purposes. In addition, it has been recently recommended by the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials for use in research and clinical settings. 13 The BPI assesses two central aspects of pain (severity and interference). It has been translated into more than 15 languages, 14 and has excellent reliability and validity. 12,15 The BPI has been validated in cancer patients, 16 in AIDS patients, in other populations suffering from physical pain (e.g., in Fabry disease patients, in mammography patients, etc. 15 ), and recently among veterans suffering from chronic nonmalignant pain treated at a specialized chronic pain center. 16 However, despite the high comorbidity between PTSD and pain, the BPI has yet to be validated in a psychiatric population where the primary diagnostic condition is PTSD. The validation of the BPI in such a population would not only give further support to the psychometric properties of the BPI in populations other than those suffering from cancer, but more importantly, would be essential for the appropriate screening and assessment of pain in veterans suffering from PTSD. The purposes of this study were 1) to validate the BPI for use in a population of veterans with high levels of PTSD symptoms and 2) to document the prevalence of pain in such a sample. Methods Sample and Procedure The sampling pool consisted of Frenchspeaking Canadian male veterans assessed or treated at the National Center for Operational Stress Injuries at Ste. Anne s Hospital, a Veterans Affairs Canada outpatient clinic located in Montreal. This institution specializes in the treatment of trauma-related disorders. Due to insufficient numbers, we excluded from the study the clinic s female clients (<10%). Most clients were young veterans who participated in United Nations and North Atlantic Treaty Organization peacekeeping operations (86%), while a small subgroup was composed of older World War II and Korean veterans (14%). Potential participants (n ¼ 340) were invited by phone to participate in the study by a member of the clinic s staff, and were mailed a booklet of questionnaires along with an informed consent form. Either during this call, or after the mailing of the survey, 72 individuals were found to meet one of our exclusion criteria (poor cognitive functioning, inability to read French, or having no current mailing address), yielding a pool of 268 potential participants, of which 50% participated in the study. Study completers were reimbursed CDN$20 for their time and efforts. The study was approved by the Douglas Hospital Ethics Board Committee. Instruments The following reliable and valid French versions of self-report questionnaires were used for this study: The BPI, 9 a two-factor instrument that measures pain severity and pain interference. The pain severity factor has four items, all rated on a 0 ¼ No pain to 10 ¼ Pain as bad as you can imagine Likert scale. The pain interference factor has seven items, all rated on a 0 ¼ Does not interfere to 10 ¼ Interferes completely Likert scale. The BPI has shown high reliability and validity among different populations; 15 Cronbach s

3 722 Poundja et al. Vol. 33 No. 6 June 2007 alphas are typically over The BPI is highly correlated with other measures of pain, disability, and health status. 15 In the French validation study in cancer pain, alphas were high, ranging from 0.86 to The PTSD Checklist (PCL), 18,19 a 17-item self-report questionnaire that assesses PTSD symptoms in the last month. The PCL is highly correlated with one of the most widely accepted structured interviews for PTSD, the Clinician Administered PTSD Scale, r ¼ The World Health Organization Quality of Life dbrief Measure (WHOQOL-BREF), 21 a 26- item instrument that assesses four domains of quality of life (i.e., physical, environmental, psychological/spiritual, and social relationships/body image). Only the physical health subscale was used for the purposes of this study, as a means to assess convergent validity with the BPI. The WHOQOL-BREF was translated from English to French, and back translated by a team of professional translators at Ste. Anne s Hospital, under the guidance of two bilingual psychologists (AB and SG). In our sample, the Cronbach s alphas for the instrument and for the physical subscale were, respectively, 0.93 and The Short Form Health Survey (version 2) (SF- 12), 22 a 12-item instrument that assesses functional health status, including bodily pain. Other health status components measured by this instrument are physical functioning, role limitations due to physical problems, social functioning, general mental health, role limitations due to emotional problems, vitality, and general health perceptions. The SF-12 was used to assess convergent validity with the BPI, as has been done in previous studies. 15,23 The Marlowe-Crowne Social Desirability Scale- Form C (MC-Form C), 24,25 a 13-item, true/false scale instrument, which assesses the tendency to respond in a socially desirable (or undesirable) manner. The MC-Form C has demonstrated good to excellent internal consistency. 25 Data Analyses We conducted the analyses using SPSS version All tests were two-tailed. The amount of missing data was extremely low; therefore, we did not use any data imputation procedure. We computed internal consistency estimates of reliability in the form of Cronbach s alphas for the two scales of the BPI. We examined the factor structure of the BPI, using an exploratory factor analysis with promax rotation. We selected promax because it makes no assumption as to whether the factors are orthogonal or oblique. We calculated convergent validity with Pearson s correlations between the BPI scales, the SF-12, and WHOQOL- BREF physical scale. Finally, we used 95% confidence intervals (CIs) to compare different groups of patients on their pain severity. Results Sample Characteristics This study included 131 veterans, of which one was removed from statistical analyses because of erratic responses. This yielded a final sample size of 130 veterans, with a mean age of (SD ¼ 13.70), ranging from 28 to 81 years old. Approximately half (46.2%) the sample was married, 22.3% were living in a commonlaw union, 17.7% were single, 13.1% were divorced, and 0.8% were widowed. The sample was primarily Caucasian (96.9%). Most veterans (69.2%) reported having served in the Armed Forces, while a small percentage (7.7%) reported having served in the Navy, in the Air Force (13.8%), both the Armed and Air Forces (6.9%), or in all three categories (2.3%). A total of 4.6% participants had never been deployed, 52.3% were deployed once or twice, 27% three to four times, and 13.8% five or more times; 3.8% failed to report such information. Probably central in the development of their PTSD, the most stressful overseas deployment locations identified included Ex-Yugoslavia (n ¼ 47), Cyprus (n ¼ 16), Haiti (n ¼ 11), Korea (n ¼ 10), and the Persian Gulf (n ¼ 7). Nineteen veterans had been deployed only in Canada. Of the final sample, 10.8% experienced their most stressful deployment before or by 1955, 1.5% between 1956 and 1965, 6.2% between 1966 and 1975, 9.2% between 1976 and 1985, 44.6% between 1986 and 1995, and 24.6% between 1996 and 2004; 3.1% did not report any date. PTSD diagnosis was evaluated using the DSM-IV-TR (Diagnostic and Statistical Manual of Mental Disorders, 4th ed., text revision) 26 criteria with the PCL. Eighty-five percent of the sample met criteria for a diagnosis of current PTSD. However, all of the subjects were

4 Vol. 33 No. 6 June 2007 BPI in Canadian Veterans Suffering from Traumatic Stress 723 previously assessed or currently treated for PTSD. All following analyses included all 130 participants. Removing the participants not suffering from current PTSD (n ¼ 18) from the analyses did not significantly change any of the results. Internal Consistency Table 1 shows the scores on the BPI. As can be seen, veterans in this study reported significant pain severity and interference. Internal consistency was assessed by calculating Cronbach s alphas for pain severity and pain interference. As shown in Table 2, both standardized Cronbach s alpha coefficients were equal to or above 0.90, demonstrating very high internal consistency. A Pearson s correlation conducted between the BPI pain severity and interference scales yielded a correlation of r ¼ 0.64, P < Construct Validity We computed the Bartlett s Test of Sphericity, which indexes the strength of the relationship among variables in the population correlation matrix; if the correlation matrix is an identity matrix, the factor model is inappropriate. This test yielded an approximate c 2 (55) ¼ , P < 0.001, suggesting the factor model is appropriate for examining the structure of the BPI in this sample. We then conducted an exploratory factor analysis, and calculated factor loadings using principal components analysis with promax rotation. The screen plot revealed two factors with an Table 1 Means, Standard Deviations, and 95% CIs of the Items of the BPI (n ¼ 130) Mean SD 95% CI Pain severity e5.6 Pain worst e7.2 Pain least e4.0 Pain average e5.9 Pain now e5.7 Pain interference e6.1 General activity e6.2 Mood e6.6 Walking ability e5.2 Normal work e6.5 Relations e6.0 Sleep e7.0 Enjoyment of life e5.7 Pain Severity Alpha ¼ 0.90 Table 2 Cronbach s Standardized Item Alphas of the BPI (n ¼ 130) Alpha if Item is Deleted Pain Interference Alpha ¼ 0.92 Alpha if Item is Deleted Pain worst 0.89 General activity 0.90 Pain least 0.90 Mood 0.90 Pain average 0.83 Walking ability 0.92 Pain now 0.85 Normal work 0.90 Relations 0.90 Sleep 0.91 Enjoyment of life 0.91 eigenvalue larger than 1. As shown in Table 3, the two-factor oblique solution explained 73% of the total variance of the BPI, a very large amount. The first factor consisted of all seven pain interference items and explained 61% of the variance, while the second factor included all four pain severity items, accounting for an additional 12% of the variance. We assessed convergent validity for the BPI, using two questionnaires that would be expected to tap different but similar constructs: the physical health subscale for quality of life (WHOQOL-BREF) and the seven health status (SF-12) subscales (including bodily pain). The Pearson s correlations between these scales and the BPI, shown in Table 4, ranged between 0.22 and 0.69 and were all significant at P < 0.01 (except for one correlation, between pain severity and health status [role emotional], significant at P < 0.05). Notably, the BPI pain severity and interference scales correlated with the health status (SF-12) bodily Table 3 Factor Structure of the BPI (n ¼ 130) Factor 1 Factor 2 Eigenvalue ¼ 6.68 (60.73%) Eigenvalue ¼ 1.34 (12.20%) Pain severity Pain worst Pain least Pain average Pain now Pain interference General activity Mood Walking ability Normal work Relations Sleep Enjoyment of life

5 724 Poundja et al. Vol. 33 No. 6 June 2007 Table 4 Convergent Validity, Pearson s Correlations Variable Pain Severity Pain Interference Quality of life, physical domain a Health status b Physical functioning Role physical Bodily pain General health Vitality Social functioning Role emotional 0.22 c 0.41 Mental health All correlations are significant at P < 0.01 (two-tailed) unless otherwise indicated. a WHOQOL-BREF. b SF-12. c Correlation is significant at P < 0.05 (two-tailed). pain scale, respectively at 0.69 and 0.65, P < 0.01, and with the quality of life (WHO- QOL-BREF) physical subscale, respectively at 0.63 and 0.63, P < 0.01, indicating the convergent validity of the BPI was good when compared with other, similar subscales. The Pearson s correlations conducted between the BPI pain severity and interference scales and the MC-Form C yielded, as expected, absence of any association between social desirability and pain, as evidenced by correlation coefficients of r ¼ and r ¼ 0.022, respectively. This indicated that social desirability did not influence self-reports of pain severity and interference. Incidence of Pain The incidence of clinically significant pain in this sampledusing a rating of five or above on the worst pain item of the BPI 12 dwas high. We found that 86.9% (95% CI ¼ 81.1% e92.7%) of our sample reported significant current pain. Using the classification of Serlin et al., 17 we found similar results: 3.1% of the veterans reported no pain (score of 0 on the worst pain item), 10% mild pain (score of 1e4), 17.7% moderate pain (score of 5e6), and 69.2% severe pain (score of 7e10). Comparisons of Pain Severity To compare our data with that of other samples, we computed 95% CIs using the means and standard deviations of the BPI worst pain severity subscale. As can be seen in Table 5, our findings suggest that veterans treated for Table 5 BPI Worst Pain Item Comparisons Among Different Pain Samples Sample and Reference No. Mean 95% CI Veterans treated at a chronic e8.45 pain center 16 Neuropathic pain e8.24 Cancer pain (China) e7.48 Veterans treated for PTSD e7.19 (our sample) Cancer pain (Philippines) e6.69 Cancer pain (USA) e6.14 Cancer pain (France) e6.20 Diabetic peripheral neuropathy pain e5.94 PTSD suffer from levels of pain severity that are similar to that of patients suffering from neuropathic and cancer pain. 16,17,27,28 Strikingly, our findings also suggest that veterans are reporting higher pain severity from other samples suffering from cancer in the United States and in France, as well as from diabetic peripheral neuropathy pain. Only the veterans treated at a chronic pain center report more pain severity than the veterans treated for PTSD in our sample, which is to be expected given that only those with the highest level of pain would be expected to be treated at a chronic pain clinic. Discussion In this study, we found that veterans with PTSD were suffering from high levels of pain: 86.9% of our sample reported significant current pain. In extant literature, high co-occurrence rates have been found in various populations, and particularly among combat veterans suffering from chronic PTSD; for instance, 80% reported chronic pain in a previous study. 5 Our findings parallel these findings, but with current PTSD and pain. Perhaps more importantly, we found that when compared to various other medical populations on pain severity, the veterans in our study suffered from equivalent or higher levels of pain (with the exception of veterans treated at a chronic pain center). Overall, these findings suggest pain is an important co-occurring condition that needs to be taken into consideration when treating PTSD patients.

6 Vol. 33 No. 6 June 2007 BPI in Canadian Veterans Suffering from Traumatic Stress 725 Another goal of this study was to validate the BPI among Canadian veterans seeking assessment or treatment for deployment-related PTSD. The BPI scales showed excellent internal consistency, with alpha coefficients among the highest that can be found in the BPI literature. 15,29 A factor analysis confirmed previous findings on the two-factor internal structure of the BPI, and explained a very high percentage of the total variance of the instrument. Further support for the validation of the BPI scales came from convergent validity analyses, that is, correlations between the BPI scales, the health status scale (SF-12), and the scale on quality of life in the physical domain from the WHOQOL-BREF. In light of our results, BPI showed robust reliability and validity in our sample. Study s Strengths and Limitations Our study has a number of strengths that are important to note. First, ours is the first study to validate the BPI in a psychiatric population. Second, our study parallels the findings of Beckham et al. 5 on the high incidence rate of pain in PTSD veterans, but with current pain. Finally, this study provides us with some comparisons among different samples of patients suffering from pain. Among the limitations of our study, one should keep in mind that correlational study designs, like the one we used, preclude drawing conclusions about the direction of causation between PTSD and pain. Future studies should, therefore, explore such issues in a longitudinal design in more ethnically diverse samples of both genders. Self-report measures preclude making firm and valid clinical diagnoses: we did not assess in this study for medical or injury history, and future studies on PTSD and pain should assess these important variables. Finally, we used a convenience sample, and lack of information on nonrespondents precludes testing for potential response bias. The findings of our study have important clinical implications, and treatment of PTSD in veteran populations should include careful screening for pain: PTSD and pain seem to highly co-occur in this population, the level of pain seems very high, and as has been shown recently, 6,7 both can mutually maintain or exacerbate each other. We recommend the use of the BPI in veteran populations for screening purposes, and suggest that validation of the BPI continues in other psychiatric populations as well. Acknowledgments The authors would like to thank the clients and mental health professionals at St. Anne s Center for their participation in and support of this study. References 1. Asmundson GJ, Norton GR, Allerdings MD, Norton PJ, Larsen DK. Posttraumatic stress disorder and work-related injury. J Anxiety Disord 1998; 12(1):57e McFarlane AC, Atchison M, Rafalowicz E, Papay P. Physical symptoms in post-traumatic stress disorder. J Psychosom Res 1994;38(7):715e Muse M. Stress-related, posttraumatic chronic pain syndrome: criteria for diagnosis, and preliminary report on prevalence. Pain 1985;23(3): 295e Benedikt RA, Kolb LC. Preliminary findings on chronic pain and posttraumatic stress disorder. Am J Psychiatry 1986;143(7):908e Beckham JC, Crawford AL, Feldman ME, et al. Chronic posttraumatic stress disorder and chronic pain in Vietnam combat veterans. J Psychosom Res 1997;43(4):379e Asmundson GJ, Coons M, Taylor S, Katz J. PTSD and the experience of pain: research and clinical implications of shared vulnerability and mutual maintenance models. Can J Psychiatry 2002; 47(10):930e Sharp TJ. The prevalence of post-traumatic stress disorder in chronic pain patients. Curr Pain Headache Rep 2004;8(2):111e Poundja J, Fikretoglu D, Brunet A. cooccurrence of PTSD symptoms and pain: is depression a mediator? J Trauma Stress 2006;19(5):747e Cleeland CS. Measurement of pain by subjective report. In: Chapman CR, Loeser JD, eds. Issues in pain measurement, Advances in pain research and therapy, vol. 12. New York: Raven Press, 1989: 391e Melzack R. The McGill Pain Questionnaire: major properties and scoring methods. Pain 1975;1(3): 277e Cleeland CS. Pain assessment in cancer. In: Osoba D, ed. Effect of cancer on quality of life. Boca Raton, FL: CRC Press, Inc, 1991: 293e305.

7 726 Poundja et al. Vol. 33 No. 6 June Cleeland CS, Ryan KM. Pain assessment: global use of the Brief Pain Inventory. Ann Acad Med Singap 1994;23(2):129e Dworkin RH, Turk DC, Farrar JT, et al. Core outcome measures for chronic pain clinical trials: IMMPACT recommendations. Pain 2005;113:9e Zelman DC, Gore M, Dukes E, Tai K, Brandenburg N. Validation of a modified version of the Brief Pain Inventory for painful diabetic peripheral neuropathy. J Pain Symptom Manage 2005;29:401e Keller S, Bann CM, Dodd SL, et al. Validity of the Brief Pain Inventory for use in documenting the outcomes of patients with noncancer pain. Clin J Pain 2004;20(5):309e Tan G, Jensen MP, Thornby JI, Shanti BF. Validation of the Brief Pain Inventory for chronic nonmalignant pain. J Pain 2004;5(2):133e Serlin RC, Mendoza TR, Nakamura Y, Edwards KR, Cleeland CS. When is cancer pain mild, moderate or severe? Grading pain severity by its interference with function. Pain 1995;61(2): 277e Ventureyra VA, Yao SN, Cottraux J, Note I, De Mey-Guillard C. The validation of the Posttraumatic Stress Disorder Checklist Scale in posttraumatic stress disorder and nonclinical subjects. Psychother Psychosom 2002;71(1):47e Weathers FW, Litz BT, Herman DS, Huska JA, Keane TM. The PTSD Checklist (PCL): reliability, validity, and diagnostic utility. Paper presented at the 9th Annual Conference of the International Society for Traumatic Stress Studies, San Antonio, TX, Blanchard EB, Jones-Alexander J, Buckley TC, Forneris CA. Psychometric properties of the PTSD Checklist (PCL). Behav Res Ther 1996;34(8): 669e The WHOQOL Group. Development of the World Health Organization WHOQOL-BREF quality of life assessment. The WHOQOL Group. Psychol Med 1998;28(3):551e Ware JEJ, Kosinski M, Turner-Bowker DM, Gandek B. How to score version 2 of the SF-12 Health Survey (with a supplement documenting version 1). Lincoln, RI: QualityMetric Incorporated, Radbruch L, Loick G, Kiencke P, et al. Validation of the German version of the Brief Pain Inventory. J Pain Symptom Manage 1999;18(3):180e Crowne DP, Marlowe D. A new scale of social desirability independent of psychopathology. J Consult Psychol 1960;24:349e Reynolds WM. Development of reliable and valid short forms of the Marlowe-Crowne Social Desirability Scale. J Clin Psychol 1982;38(1):119e American Psychiatric Association. Diagnostic and statistical manual of mental disorders. Text revision (DSM-IV-TR), 4th ed. Washington, DC: American Psychiatric Association Press, Backonja M, Stacey B. Neuropathic pain symptoms relative to overall pain rating. J Pain 2004; 5(9):491e Gore M, Brandenburg NA, Dukes E, et al. Pain severity in diabetic peripheral neuropathy is associated with patient functioning, symptom levels of anxiety and depression, and sleep. J Pain Symptom Manage 2005;30(4):374e Cleeland CS, Nakamura Y, Mendoza TR, et al. Dimensions of the impact of cancer pain in a four country sample: new information from multidimensional scaling. Pain 1996;67(2e3):267e273.