A randomised controlled trial of acupuncture care for persistent low back pain: cost effectiveness analysis

Introduction

In a national survey carried out on behalf of the Department of Health in England and Wales, 40% of the adult population reported having experienced back pain within the preceding 12 months.1 The annual cost of low back pain to the United Kingdom's health service has been estimated at £480m (€703m; $901m), with the annual cost to a general practice with a list size of 10 000 patients estimated at £88 000 in 1994.2 A recent study estimated that the economic burden of low back pain in lost productivity and disability or sickness benefits is £10 668m per year.3

The use of acupuncture as an approach for the management of chronic pain, including low back pain, is receiving increasing recognition from both the public and professionals. Several randomised trials on this topic have, however, been criticised for their quality.4 We assessed the cost effectiveness of acupuncture for the treatment of persistent non-specific low back pain.

Methods

Patients (n = 241) with persistent non-specific low back pain of 4-52 weeks' duration, who were diagnosed as suitable for management in primary care, were recruited to the trial through referral from 43 general practitioners. Patients were randomly allocated either to receive up to 10 acupuncture treatments over three months from acupuncturists trained in traditional Chinese medicine (n = 161) or to receive usual care only (n = 81). Randomisation was in a ratio of 2:1 to the offer of acupuncture to test for effects between acupuncturists. The primary clinical outcome was the bodily pain dimension on the SF-36, measured at 12 and 24 months. After adjusting for baseline score and for any clustering by acupuncturist, we found an estimated intervention effect of 5.6 points (95% confidence interval −0.2 to 11.4, P = 0.06) at 12 months (n = 213) and 8.0 points (2.8 to 13.2, P = 0.003) at 24 months (n = 182; see accompanying clinical paper for details).5 The difference in final pain scores between groups was small, about 10%-15% that of the usual care group. Costs were measured from both an NHS and a societal perspective. Effectiveness was measured as quality adjusted life years (QALYs) gained. Costs were measured in sterling prices for 2002-3. The primary economic analysis is over the 24 month period, as this incorporates comprehensive data on differentials for resource use and provides the most accurate assessment of costs and QALYs gained in the longer term.6

Results

Table 2 shows the baseline characteristics of those patients receiving acupuncture care or usual care for persistent non-specific low back pain who completed the SF-36 at all four time points (for whom SF-6D and QALY scores could be calculated) compared with those patients with missing SF-36 data at any time point. The group with complete data also formed the sample for the base case analysis of cost effectiveness.

Compared with the base case sample, patients who were excluded were less likely to be in full time employment and to report more than five previous episodes of back pain.

Patients in the acupuncture group had an average of eight sessions with a study acupuncturist (table 3). Seven patients in the acupuncture group and nine in the usual care group received NHS acupuncture during the trial period. Several patients in the acupuncture arm (n = 19) purchased additional private acupuncture.

An improvement was found in health related quality of life over the 24 months in both groups, with the acupuncture arm reporting a slightly higher mean health related quality of life score at 24 months (table 3). With the exception of acupuncture, the mean differences between groups were not statistically significant at any time point.

Table 4 documents the mean NHS costs of healthcare resource use for low back pain treatment during the trial. The costs of initial acupuncture treatment differed significantly between the groups. The total mean costs of treatment to the NHS for the acupuncture group (£471.10) were higher than for the usual care group (£332.24) and the difference was statistically significant. The initial acupuncture treatment accounts for about 45% of the total NHS costs of treatment for the acupuncture group.

Overall the incremental cost effectiveness ratio for acupuncture in the treatment of low back pain was positive (table 5), with a mean of £4241 at 24 months. The figure shows the probability of the intervention being cost effective using the base case data for a range of cost effectiveness ceilings. Assuming an implicit threshold of a maximum willingness to pay of £20 000 for a QALY, the probability of the cost per QALY of acupuncture for low back pain falling below this threshold value was over 90%.

Cost effectiveness acceptability curve of acupuncture for persistent non-specific low back pain using base case data for range of cost effectiveness ceilings

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Discussion

Acupuncture treatment for persistent non-specific low back pain confers a modest benefit to health, as measured by quality adjusted life years (QALYs), at relatively minor extra cost to the NHS compared with usual care. This finding is complemented by the clinical results detailed in the accompanying paper, which found weak evidence of an effect on pain at 12 months but stronger evidence of a small benefit at 24 months.5 We estimated the incremental cost effectiveness to be £4241 per QALY gained in the base case. This represents a conservative estimate because it excludes cost savings associated with productivity gains. From a societal perspective when gains in productivity are included then acupuncture care for low back pain becomes dominant in that it is less expensive and confers greater health benefits than usual care. It is likely, however, that this represents an underestimate of the cost per QALY because the quality of life measure will in part take into account this improved productivity.

A potential limitation of the cost effectiveness study relates to the use of a patient completed questionnaire to obtain information on use of resources. This method can be criticised on the basis that it may be the subject of recall bias. On a practical level, however, this method offers an appropriate and efficient mechanism for obtaining this information. To minimise the risk of recall bias for hospital episodes related to low back pain, the date and duration of hospital stays were collected from the resource use questionnaire and cross referenced directly with the relevant hospital. A further limitation is the proportion of missing data for the base case analysis. This amount of missing data is not unusual for community based interventions and also reflects the extended duration (24 months) of the randomised controlled trial. Principally this indicates failure of a proportion of patients to complete the SF-36 at all four time points. Although the amount of missing data may affect the generalisability of the findings, the characteristics of patients excluded from the base case analysis were broadly similar to those who were included.

We assessed the cost effectiveness of acupuncture treatment for low back pain using systematic and transparent methods. A previous study assessed the cost effectiveness of acupuncture for headache using similar methods to those reported here but over a shorter period (12 months) and estimated the incremental cost effectiveness ratio to be £9180.18 As the authors note, however, the incremental cost effectiveness ratio is likely to reduce over longer periods because of increased gains in QALYs. It is difficult to assess the extent to which our results are comparable to those of other studies assessing interventions for low back pain because few studies have assessed the relative costs and effectiveness of treatments for low back pain. Studies have tended to assess effectiveness or costs in isolation and have tended not to use a generic outcome measure such as QALYs that would facilitate comparisons across alternative interventions. One study concluded that chiropractic treatment was more effective than outpatient management for patients with chronic or severe low back pain but did not assess the relative costs of each intervention.19 More recently trials have been reported of physiotherapy, exercise, and manipulation for low back pain.²⁰²¹ The trial of physiotherapy did not report cost effectiveness.20 The United Kingdom back pain exercise and manipulation trial showed exercise to have an incremental cost effectiveness ratio of £8300 compared with “best care,” but it did not compare interventions with usual care.21 The open and pragmatic nature of our trial allowed acupuncture care to be compared with usual care in everyday practice. Given that usual care comprised a mix of interventions,5 it was, however, not possible to isolate the costs and effectiveness of individual treatments as part of the package of usual care.22

Recent guidance from NICE indicates that a ceiling ratio of £20 000 per QALY represents the threshold of what the NHS can afford to pay for additional QALYs, unless other arguments exist for adopting the technology.6 If £20 000 is taken as the maximum acceptable cost effectiveness ratio, then acupuncture for the treatment of low back pain seems cost effective.

On the basis of our findings of cost effectiveness, longer term reduction in pain, and the acceptability of acupuncture care to patients as reported in the accompanying clinical paper,5 commissioners of musculoskeletal services would be justified to consider making available the referral of patients in primary care to a short course of traditional acupuncture care for persistent non-specific low back pain.

An evidence base showing the cost utility of acupuncture and other short term packages of care, such as massage, osteopathy, chiropractic, or physiotherapy could facilitate the development of NHS policy on the basis of affordability and allow patients with low back pain to choose their treatment.