The Effect of Monochromatic Infrared Energy on Sensation in Subjects With Diabetic Peripheral Neuropathy: A Double-Blind, Placebo-Controlled Study: Response to Clifft et al.

The recent paper by Clifft et al. (1) concludes that monochromatic infrared energy (MIRE) is no better than placebo MIRE in restoring sensation in the lower extremities of subjects with diabetes. We would like to suggest an alternative conclusion.

First, the subjects were treated with a MIRE device that delivered photo energy and therapeutic heat at a lower level than has been used in other clinical studies. Treatment times per session were also only 66% of those reported by Leonard et al. (2). As a result, each subject received ∼50% less photo energy than used in the Leonard protocol. The clinical effect of phototherapy treatment is time dependent. In and of itself, this difference in treatment protocol may account for the authors’ inability to obtain results similar to those reported by Leonard et al. (2).

Second, while many subjects who cannot sense the larger 6.65 Semmes-Weinstein monofilament (SWM) at any site are unlikely to obtain sensation to the 5.07 SWM during a course of 12 treatments, it is possible that sensation to an intervening monofilament (for example, a 5.65 monofilament) may actually occur (2,3). These data were omitted from the article.

Third, subjects were selected solely on “… self-diagnosed…” diabetes and their inability to detect the 5.07 SWM at one of four sites on either foot. It is likely that a number of the subjects did not have diabetic peripheral neuropathy, since many exhibited sensory loss in only one limb and/or at only one site. The selection and treatment of subjects was further confounded by the fact that while some subjects received active treatment on one extremity and placebo treatment on the other, some received active or placebo treatment on both extremities.

Finally, the authors neither used a forced-choice method of SWM testing nor required the patient to specify the location at which they sensed the SWM; these are preferred testing methodologies using the SWM as it was used in other studies (2,3). Since it is well known that subjects responding to a SWM may specify a location other than that which is actually being touched, the SWM data obtained may be less accurate than it could have been, possibly explaining the apparent improvement in the placebo-treated limbs.

We believe that the reported conclusion may be attributed to the variance of the treatment dosage (amount of photo energy delivered). Additionally, it is important that utmost care is required in properly administering an SWM test to maximize the reliability of the data obtained.