Background
Musculoskeletal problems are extremely common in our population, especially neck pain and its associated disability [
1]. The therapy for neck pain includes relieving of pain, stiffness and disability through treatments which may include exercise, traction, acupuncture, mobilization and manipulation [
2,
3]. To determine whether or not specific treatments are effective for the various causes of neck pain, appropriate patient outcomes must be recorded.
Clinical outcome measures such as self-report questionnaires are useful in monitoring patient improvement during treatment. The vast majority of disease-specific instruments have been developed in English- speaking countries [
4]. The most commonly used neck pain specific questionnaires are the Neck Disability Index (NDI) [
5], the Northwick Park Neck Pain Questionnaire [
6], the Copenhagen Neck Functional Disability Scale [
7], the Neck Pain and Disability Scale (NPAD) [
8], and the Bournemouth Questionnaire for Neck Pain (BQN) [
9]. The NDI is the most commonly used instrument in neck pain research [
9].
Neck pain, similar to low back pain is a multidimensional experience, best described by the biopsychosocial model that includes pain, disability, cognitive and affective domains [
9]. However, many of the current neck pain questionnaires such as the NDI measure only pain and disability. The BQN was developed from the biopsychosocial model and includes questions on psychosocial issues as well as pain and disability. The BQN is a short-form, multidimensional instrument originally created in English, that has been shown to be valid, reliable and responsive for use in the clinical and research settings [
9].
In order to use the BQN in a German speaking patient population it is not enough to just translate the items well linguistically, because that does not guarantee similar measurement properties [
10]. The questionnaire also has to be adapted cross-culturally, which means employing a process that looks at both language and cultural issues relevant to the German speaking population in which the questionnaire will be used [
4].
As the BQN is only available in English, French and Dutch [
9,
11,
12], the purpose of this study was to translate and validate a German version.
Discussion
The Bournemouth questionnaire for neck pain (BQN) is a relatively new, short form multidimensional instrument developed from the biopsychosocial model and includes question items on pain, disability, cognitive and affective domains [
9]. Currently the BQN has been translated and validated in English, French and Dutch [
9,
11,
12]. The purpose of this study was to translate and test a German version of the BQN for use in clinical practice and research. The BQN was tested against the NDI, the most commonly used questionnaire for neck pain and the NPAD which also contains biopsychosocial questionnaire items [
9]. Both the NDI and NPAD have been translated and validated in German.
The 6-step translation and cross cultural adaptation process after Beaton, Bombardier et al. [
4] was used in this study and included forward and back translations, validation by an expert committee, face validity and testing in neck pain patients followed by statistical analysis. One of the analyses investigated was test-retest reliability. Although the results indicated excellent reliability (0.91-0.99), one possible source of error was the 2 hour retest time period. Terwee et al. [
14] recommend that a time period of less than 1 day is too short as there is a high chance that patients can remember their previous answers. This may have been the case, however other research has confirmed a high level of test-retest reliability for the BQN in other studies [
9,
11,
12].
When using outcome measures such as questionnaires, it is important that the instrument is appropriate for the patient population and setting in which it is used. Although content validity was not specifically evaluated in this study, as it was already established in the original English version [
9], it would have been optimal to also repeat this step for the German version of the questionnaire as recommended by Terwee et al. [
14]. However, the percentage of the maximum questionnaire score reported by patients at baseline, internal consistency and standardized response means (SRM) are three measures that may provide an indication of the instrument's suitability for use with the patient population under investigation. A comparison of the 3 questionnaire's mean total scores at baseline indicated that 47% of the maximum total score of the BQN was reported by neck pain patients compared to 35% for the NPAD and 28% for the NDI. These results suggest that the BQN is well positioned in the mid range to be able to monitor chiropractic patients' change during treatment either positively or negatively. On the other hand the NPAD and NDI mean scores were in the lower range and may predispose them to floor effects (i.e. baseline scores too low) and potentially underestimate patients' improvement. A further analysis of the mean scores for each of the 10 NDI questionnaire items at baseline identified low mean scores ranging from 0.73 (SD 0.88) to 1.67 (SD 1.22). The exception was pain intensity with a mean score of 2.23 (SD 1.1). This again raises the question of a floor effect and underestimation of patient improvement for the NDI and NPAD.
Another possible interpretation of the previous results is that the NDI is more suited to an acute patient population. Patients are asked to fill out the NDI according to how they feel 'right now' as opposed to the BQN which asks them 'over the past week'. Consequently the NDI may be more suitable for patients whose complaint started within the past few days and the BQN for patients whose pain complaint began possibly a minimum of 5 to 7 days previously. On review, the NPAD would seem to fit in between the NDI and BQN as patients are not given clear instructions (with the exception of pain intensity) as to what time frame to use in order to answer the questions.
Similar to previous studies, the internal consistency of the BQN indicated that all of the 7 questionnaire items were acceptable and well above the 0.2 Cronbach α cut-off point achieving a 0.79 for total pre-treatment scores and 0.82 for total post-treatment scores [
9,
12,
13]. These findings confirm that all of the questionnaire items are relevant to the patient population studied and that they all are necessary, measure the same construct, and contribute to the total score. Nevertheless our results did suggest that question item 7 for pain locus of control, while still important, contributed the least to the BQN total score. This result was also found by Bolton and Humphreys [
9] where question 7, although well above the 0.2 Cronbach α, was considerably lower than the other items at pre-treatment and retest. However this was not the case for the Danish translation and validation study for the low back version of the BQ [
13]. Further work might be indicated in this area as the question 7 subscale was also difficult to match with the NPAD and impossible to match with the NDI. The correlation between question 7 on the BQN and question 20 on the NPAD prior to treatment, although statistically significant, was much lower (r = .24) than the correlations for all of the other subscales.
The standardized response means (SRM) identified that the BQN is more sensitive to change in this patient population compared to the NDI and NPAD. This corresponds to similar results by Bolton and Humphreys [
9] who compared the BQN to the NDI and Copenhagen Neck Functional Disability Scale and Hartvigsen et al. [
13] who compared the BQN to the SF-36, although this was done for low back rather than neck pain. Taken together, these results confirm that the BQN is able to detect small clinical changes that are important to neck pain patients, thus emphasizing its utility as a useful and appropriate instrument for assessing this patient population. It has been suggested previously [
9] that the BQN is more sensitive to change due to its multidimensional composition. A comparison of the subscales for the 3 questionnaires (Figure
2 and table
5) demonstrates that the NDI does not contain items to assess the cognitive or affective domains, particularly related to psychological impairment (attitudes, beliefs and behaviors) manifested in patients as anxiety, depression, emotions or work related fear-avoidance.
When comparing the SRMs in terms of the sensitivity for each subscale for the 3 questionnaires, it is interesting to note that all seven of the scales (questions) for the BQN are more sensitive than the NPAD or NDI. One possible reason is that the NDI asks patients to respond to each item as they are at present. As patients' pain experience is known to fluctuate, patients' pain experience today may not be representative of their overall neck pain experience [
18]. The BQN however asks patients to respond in terms of their average experience over the past week which may be more representative. As mentioned previously, the NDI may be more suited to an acute neck pain population whose pain complaint began in the past few days. The NPAD on the other hand seems to be suitable for patients in between the NDI (current) and the BQN (past week). A possible explanation for this is that the NPAD does not clearly state (other than for pain intensity) what time frame patients should use to answer each of the items. For pain intensity, the instructions are specific, asking for current or worst pain or best pain. However for the other items, it is not clear whether the patient should respond as of now, today, on average over the past week or taking their current episode into consideration.
Acknowledgements
The authors thank Jennifer Bolton, PhD, MA Ed, for her advice during the study. The authors also thank Thomas Hausheer, DC and Karin Mühlemann, MS, (library and information science) for doing the English to German translations as well as Rhonda Schmid, DC and Rosemary Oman, DC for doing the back translations. Additional members of the expert committee that the authors wish to thank are Florian Brunner MD and Daniel Mühlemann PT, DC for providing valuable input toward the final version of the German BQN. Finally the authors would like to thank Sara Meier, DC and Christoph Sem, DC as well as his team at the Chiropractic Oerlikon practice for helping with the data collection.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
MS: Data acquisition, drafting and revising the manuscript, interpretation of data. CP: Concept and design of the study, analysis and interpretation of data, drafting of results section, revising manuscript. BKH: Concept and design of the study, drafting manuscript discussion section, revising manuscript. All authors read and approved the final version of the manuscript.