Wednesday, December 12, 2012

A New Way to Assess Nonspecific Back Pain

Back PainIt seems reasonable that, just as the intensity of low back pain may vary in specific situations, the measurement of pain should take into account those differences — especially when considering nonspecific low back pain. A new and simple way of scoring pain intensity takes into account postural factors that may lead to better assessments of back pain and treatment planning.

Researchers from Japan, reporting in the journal Pain Research and Treatment, note that there often appear to be clinical differences between younger and older patients in their experience of nonspecific low back pain (NSLBP) [Aoki et al. 2012]. Elderly patients often have low back pain during motion and while standing, but less pain when sitting than younger patients, and assessing these differences could be important in clinical practice.

Therefore, they devised a study to confirm these characteristic differences of NSLBP using a new detailed visual analog scale (VAS) scoring system. The researchers divided 189 patients with NSLBP into an elderly group (≥65 years old, mean 73 years; N=56, 30 males, 26 females) and a young group (>20 to <65 years old, mean 46 years; N=133, 59 males, 74 females). All had suffered back pain for at least 3 months and showed no obvious pathological findings.

VAS-scalesLow back pain was self-evaluated by patients using a traditional 0-to-10 cm VAS to indicate, overall, their worst pain during the prior week, and on the Oswestry Disability Index (ODI). The ODI is a subjective assessment tool used to measure a patient's percentage impairment (ie, how severely back pain has affected their life); higher scores indicate greater impairment. This approach was compared with a new detailed 10 cm-VAS scoring system in which pain was independently evaluated in 3 different postural situations — during motion, standing, and sitting [see figure].

Average low back pain scores on the traditional VAS were comparably moderate in both groups: 4.8 cm in the elderly group and 5.0 cm in the young group. Similarly, scores on the ODI were not significantly different: 24.6 in the elderly group and 23.2 in the young group.

The results of the detailed VAS assessments showed no significant differences between the two groups while in motion and when standing. However, as the researchers had expected, the elderly group showed significantly lower VAS scores while sitting compared with the young group; 2.8 ± 2.7 cm vs 4.2 ± 2.6 cm, respectively.

The researchers conclude that, “in consideration of our findings that no significant differences were detected using the traditional VAS evaluation and ODI, our detailed VAS may be useful not only to characterize low back pain, but also to examine treatment effects of low back pain in clinical situations.” For example, the researchers share their observation that, in some patients, their scores on a traditional VAS assessing low back pain may not change appreciably after spinal surgery; however, they nonetheless may express satisfaction with their level of low back pain reduction. In such cases, there is a possibility that one or two of the more detailed VAS scores examining pain during motion, while standing, or when sitting improved following surgery — and this made an important difference.

COMMENTARY: This was a relatively minor and simple modification of the traditional single-dimensional VAS used in many clinical situations (and research trials) to assess back pain. Even separate scales to measure pain frequency and intensity would not take into account the postural situations — motion, standing, sitting — which could make a significant difference to patients.

As the researchers suggest, a treatment might be considered acceptably successful by patients if it significantly ameliorated pain on only one or two of the dimensions. However, such improvement might go unrecognized if a single scale is used to assess pain in general, and these distinctions might also be taken into account in future research on back pain therapies. In fact, it would be interesting to add a 4th scale — low back pain while lying supine — representing an at-rest posture, to see if that also distinguishes between different age groups and back-pain conditions pre- and post-treatment.

In this present study, there was a significantly moderate effect size — which we calculated as 0.53 (Cohen’s d) — distinguishing chronic nonspecific low back pain while sitting in younger versus older patients. However, in the overall study population pain ratings on any VAS, as well as on the ODI, were in the moderate range at most; if the study could be replicated in patients with more severe back pain there might be more pronounced differences across the 3 postural dimensions, depending on individual patient condition, and this could help guide treatment planning and rehabilitation efforts.

It also would be of interest to know if other pain-rating scales individually assessing postural effects might work just as well; for example, a 0-to-11 numerical rating scale (NRS) or a pain faces scale [see the Pain-Topics sections here for various pain assessment scales]. It seems that they might be appropriate and, if so, the approach could be adapted to patient and practitioner preferences for pain-assessment tools.

REFERENCE: Aoki Y, Sugiura S, Nakagawa K, et al. Evaluation of Nonspecific Low Back Pain Using a New Detailed Visual Analogue Scale for Patients in Motion, Standing, and Sitting: Characterizing Nonspecific Low Back Pain in Elderly Patients. Pain Res Treat. 2012; 2012(680496) [available here]

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