Abstract
Dear Editor,
We read with great interest the study by Xie et al. [[1]], and appreciate its contribution, especially considering HILT's novelty. However, we have concerns to discuss.
First, the authors report functional activity with the Neck Disability Index [[2]]. NDI measures neck pain-related disability and impact on daily activities as a score or percentage. Since RCTs report NDI in terms of functional activity, using disability as the outcome is recommended. In the meta-analysis, HILT shows higher NDI scores for functional activity post-treatment compared to controls, but it is unclear if these scores signify functioning or disability.
Second, the meta-analysis used SMDs, which are recommended for handling diverse instruments or scales across multiple RCTs assessing the same outcome [[3]]. Despite consistent use of VAS, NDI, and cervical range assessments in the eight RCTs, SMDs were used to calculate the pooled effect size [[1]]. Using standardized means for data grouping is logical when measurement tools are similar. Nevertheless, SMDs can complicate the interpretation of clinically significant differences.
Third, the authors used the PEDro scale to assess bias, but Cochrane's RoB tools, seen as the gold standard for systematic reviews, offer a more comprehensive evaluation [[4]]. The authors report a low bias according to PEDro scores (4−8). However, potential inconsistencies arise when using the Cochrane RoB tool. These discrepancies are particularly notable for concealed allocation, assessor blinding, and blinding of therapists or patients, acknowledged by the authors as deficient [[5]]. With a score of 5/10 in the PEDro database, it's important to re-evaluate the Kenareh study. Also, consider revisiting Albanese et al.'s citation, as it questions the suitability of the PEDro scale for assessing quality.
Fourth, the meta-analysis had some inconsistencies. Figure 2 compared HILT with a placebo, though Shady et al. didn't use one. Figure 3 omitted cervical movement studies (Venosa, Shady and Yilmaz), and Figure 4 didn't include NDI studies (Venosa, Shady and Kenareh), potentially affecting HILT's for neck pain-related disability.
Fifth, the March 2022 update included data from eight RCTs, but four earlier studies (accessible via PubMed or open access) were not considered [6, 7, 8, 9], potentially introducing publication bias.
Lastly, the study emphasizes that HILT's depth relies on output power, unlike LLLT. Wavelength determines depth, and higher power means faster energy delivery during treatment [[10]].
These concerns could affect the evidence, its certainty, and its recommendations.
Ethical approval
N/A.
Conflict of interest
None.