PBM – PhotoBioModulation – watch out for it!

By Jan Tunér

Ever since the birth of “low level lasers” there has been no consensus about the vocabulary in this kind of medical intervention. MeSH terms of the National Library of Medicine’s controlled vocabulary thesaurus contains several terms:

LLLT; Laser Biostimulation; Laser Irradiation, Low-Power; Laser Therapy, Low-Power; Low-Level Laser Therapy; Low-Power Laser Irradiation; Low-Power Laser Therapy; Laser Phototherapy.  All in all nine names! These terms are important for indexing on PubMed. Searching for any of them means you get the whole bunch, because all “LLLT” studies are indexed with all these terms. It is important to note that there are several other names (e.g. LILT) around, not indexed by MeSH, so the situation is complicated.

All these names have their pros and cons and there has been an ongoing discussion about a choice of a common name, but everybody seems to stick to his own darling. At the 2014 joint congress of NAALT and WALT, an expert group of 15 internationally recognized scholars decided to suggest “PhotoBioModulation therapy” (PBM) as a new and general term. Adding to the confusion or getting rid of the confusion? I go for the latter, even though I used ““Laser phototherapy” in my recent book. I liked “phototherapy” and to add the light source in front of it. An important problem with PBM is that it is not indexed by MeSH, and therefore not very useful. But no longer! From November 2015 PBM is added to the above list and my recommendation is that we all kill our darlings from now on and stick to this new term. With PBM we get rid of the question “what is low” and what does “level” mean. PhotoBioModulation correctly describes what we are doing – modulating cellular events with light. Many types of light can be used, not only lasers, although lasers do have several non-replaceable advantages. The term LPBM (laser PBM), LEDPBM, broadband light PBM etc. can be used to specify the light source used. Further to that, we get rid of “biostimulation”, because what we do with the therapeutic lasers is not only stimulating but, when so called for, inhibiting.

So I go with Churchill: “It has been said that democracy is the worst form of government except all the others that have been tried.” Quote Tunér: PBM is the worst term except for all the others that have been used!

Now, on the subject of MeSH, I disagree with this very influential agency when it comes to describing PBM (sic!):

Treatment using irradiation with light at low power intensities and with wavelengths in the range 540nm-830nm. The effects are thought to be mediated by a photochemical reaction that alters CELL MEMBRANE PERMEABILITY, leading to increased mRNA synthesis and CELL PROLIFERATION. The effects are not due to heat, as in LASER SURGERY. Low-level laser therapy has been used in general medicine, veterinary medicine, and dentistry for a wide variety of conditions, but most frequently for wound healing and pain control.

The upper limit at 830 nm is of course not correct, PBM effects have even been documented with defocused CO2 lasers! The NAALT/WALT committee suggests a new definition:

A form of light therapy that utilizes non-ionizing forms of light sources, including lasers, LEDs, and broadband light, in the visible and infrared spectrum. It is a non-thermal process involving endogenous chromophores eliciting photophysical (i.e., linear and nonlinear) and photochemical events at various biological scales. This process results in beneficial therapeutic outcomes including but not limited to the alleviation of pain or inflammation, immunomodulation, and promotion of wound healing and tissue regeneration.

Are we seeing the beginning of the end of the nomenclature problem?


2014 NAALT/WALT Nomenclature Consensus Committee

Clockwise from left: Juanita Anders (Chair), Jan Bjordal (Co-Chair), Lars Hode, Peter Jenkins, Gerry Ross, Donald Patthoff, Nicolas Wise, Jerry True, Praveen Arany, Roberta Chow, Anita Saltmarche (standing), David Baxter, Patricia Trimmer, James Carroll.