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Efficacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis of randomised placebo or active-treatment controlled trials |
Chow RT, Johnson MI, Lopes-Martins RA, Bjordal JM |
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CRD summary The review concluded that low-level laser therapy reduced pain immediately after treatment in acute neck pain, and up to 22 weeks after completion of treatment, in patients with chronic neck pain. Considering the variation in treatments, and the uncertainty regarding possible bias in the small trials included, the authors' conclusions should be interpreted with a degree of caution. Authors' objectives To evaluate the effectiveness of low-level laser therapy for acute or chronic neck pain. Searching MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials (CENTRAL), Physiotherapy Evidence Database, BIOSIS Previews and AMED (Allied and Complementary Medicine) were searched, without language restriction, from inception to July 2008. Search terms were reported. Experts were consulted, and reference lists of obtained reports and textbooks scanned, in order to identify further studies. Study selection Randomised controlled trials (RCTs) or quasi-RCTs of low-level laser therapy, for participants aged 16 or over with acute or chronic neck pain, were eligible for inclusion. The diagnostic labels allowed for neck pain were reported. Lasers had to be delivered to points with tenderness, local acupuncture points, or on a grid at predetermined points overlying the neck. Control groups had to receive placebo laser (an identical inactive laser, but with an active operating panel) or an active treatment control, such as exercise. Pain relief had to be reported as a primary outcome (both before and after therapy) either on a visual analogue scale, a numerical rating scale, or by patient-reported improvement. Functional measures of disability and adverse events were also assessed. Trials where specific pathological changes (e.g. rheumatoid arthritis) could be identified were excluded.
Most included trials were of chronic, non-specific neck pain, although two were of acute pain; a variety of sites on the neck were treated (laser was applied to an average of 11 points). The mean age of patients was 43 years, mean symptom duration was 90 months, and mean baseline pain was 57mm (on a 100mm scale). Of the patients with chronic pain, 79% were women. Trials used different wavelengths of light ranging from 632.6 to 904nm; even wider variation was evident for all the other laser-related parameters (such as average output, and frequency of treatment). Patients received an average of 10 treatments. Some trials allowed specific cointerventions (e.g. analgesics, acupuncture), some did not, and some failed to report any details on cointerventions. All but two trials used placebo as a comparator (the other trials used placebo and needling, and exercise).
Two reviewers independently selected studies for inclusion, with disagreements resolved by consensus or arbitration. Assessment of study quality Trial quality was assessed using the Jadad scale, which examined reporting of randomisation, blinding, and description of drop-outs. Trials received a score between 0 and 5 points. Data extraction Data was extracted in order to calculate mean differences and relative risks (RR) with 95% confidence intervals (CI). When specific details were not reported, calculations were made from report details (when possible). Manufacturers or trial investigators were contacted if important parameter details were not reported.
Two reviewers independently extracted data, with disagreements resolved by consensus or arbitration. Methods of synthesis Weighted mean differences, standardised mean differences (SMD), or relative risks were pooled in meta-analyses using a fixed-effect model, unless heterogeneity was significant, in which case a random-effects model was used. Statistical heterogeneity was assessed using the X2 test and I2 statistic. An expert in laser therapy assessed clinical (laser) heterogeneity. Sensitivity analyses were performed to examine the effect of trial quality (trials scoring 3 or more). Publication bias was assessed by graphical plot. Results of the review Sixteen RCTs (n=820 participants) were included in the review, with sample sizes ranging from 20 to 90 participants. Jadad scores ranged from 0 to 5, with all but two trials scoring 3 or more. All trials but one were double-blinded.
Pooled data from two RCTs of acute neck pain suggested that low-level laser therapy improved pain outcomes compared to placebo (RR 1.69, 95% CI 1.22 to 2.33; I2=89%). Results (of categorical data) for five trials of chronic pain suggested even greater benefit (RR 4.05, 95% CI 2.74 to 5.98; I2=7%). Eleven trials assessed pain intensity in patients with chronic pain and found a reduction of 19.9mm (95% CI 10 to 29.7; I2=91%) compared with placebo. The pain-relieving effect persisted for up to six months. A significant improvement in disability was also seen with low-level laser therapy (SMD 1.38, 95% CI 0.39 to 2.38; I2=93%; five RCTs).
A wavelength dose-response pattern was seen (further details were reported). Reported side-effects included tiredness, nausea, headache and increased pain, but were mostly mild and there was only one difference between the treatment groups: one trial reported a significant increase in tiredness in the laser group. Half the trials though did not report side-effect data. There was no evidence of publication bias. Authors' conclusions Low-level laser therapy reduced pain immediately after treatment in acute neck pain, and for up to 22 weeks after completion of treatment, in patients with chronic neck pain. CRD commentary The review addressed a clear question and was supported by appropriate inclusion criteria. Numerous databases were searched (and other methods were used) to identify relevant studies; there was no evidence of publication bias. Suitable methods were employed to reduce the risks of reviewer error and bias for the processes of study selection and data extraction, but the authors did not report on whether such methods were used to assess study quality, which was assessed using the Jadad scale. This did not assess methods of allocation concealment, so the risk on investigator bias affecting trial results could not be ruled out. Furthermore, no information was provided on the actual levels of withdrawals and drop-outs.
All included trials had relatively small sample sizes and information was not provided on whether treatment groups (in individual trials) were comparable at baseline for likely confounders. The authors acknowledged the considerable clinical heterogeneity in laser treatment parameters, but this also seemed apparent with regard to the sites treated, diagnoses, frequencies of treatment, and uses of cointerventions; it is therefore questionable whether meta-analysis was the most appropriate method of synthesis. However, sources of heterogeneity were explored.
Although many aspects of this review were well-conducted, the considerable clinical heterogeneity seen, coupled with uncertainty regarding possible bias in the small trials included, mean the authors' conclusions should be interpreted with a degree of caution. Implications of the review for practice and research Practice: The authors stated that when treating neck pain with low-level laser therapy, irradiation of known trigger points, tender points, and symptomatic zygapophyseal joints is advisable.
Research: The authors recommended the need for a multi-centre trial to test the optimal parameter values reported in their review, using both pain intensity and functional improvement as outcomes. The authors also recommended systematic reporting of side-effects in future studies. Bibliographic details Chow RT, Johnson MI, Lopes-Martins RA, Bjordal JM. Efficacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis of randomised placebo or active-treatment controlled trials. Lancet 2009; 374(9705): 1897-1908 Other publications of related interest Guzman J. Neck pain and low-level laser: does it work and how? Lancet 2009: doi:10.1016/S0140-6736(09)61837-7. Indexing Status Subject indexing assigned by NLM MeSH Humans; Low-Level Light Therapy; Neck Pain /etiology /radiotherapy; Pain Measurement; Randomized Controlled Trials as Topic AccessionNumber 12009109918 Date bibliographic record published 18/11/2009 Date abstract record published 25/11/2009 Record Status This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn. |
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