THE CAPSAICIN TEST IN ASSESSING THE RECOMMENDATION FOR NRT
Title.
The capsaicin test in assessing the indication
for neuroreflexotherapy: a multicenter clinical trial.
Background.
The degree of activity of the Ad and C fibers
or those "sensitive to capsaicin" correlates with
the existence of non-specific low back pain and not with the
existence of other painful syndromes in that location, such
as post-herpetic neuralgia or psychosomatic syndromes. The
continuous activation of these fibers entails the liberation
of the neurotransmitters and neuromodulators that they contain
(glutamate, substance P, neurocinine A, CGRP, etc.). These
substances are responsible for prompting, transmitting and
perpetuating pain, inflammation and muscle contraction.
Available scientific evidence shows that neuroreflexotherapy
(NRT) is effective in treating mechanical disorders of the
spine. This efficacy is explained by the inhibition of the
activity of Ad and C fibers (or those "sensitive to capsaicin").
This inhibition, prompted by the stimulation of the Ad fibers
that the surgical staples implanted in the implicated metameras
produce, prevents the liberation of the neurotransmitters
and neuromodulaters contained in Ad and C fibers.
In accordance with this biological basis, NRT should be effective
in those patients in whom the continuous activation of these
fibers is a relevant physiopathological component, and not
in the rest of the cases. Thus, prior determination of the
relevance of that factor would allow for improved selection
of those cases in which the therapy should be performed with
greater views of success.
To be able to make this prior determination in a health care
setting, a simple and reliable test is needed. Available data
suggest the potential utility of a test of these characteristics.
Capsaicin is a substance which acts on contact, provoking
a depletion of the neurotransmitters and neuromodulators contained
in the Ad and C fibers, hindering their prolonged liberation.
The capsaicin test consists of applying an ointment with
this substance on the painful area three times daily for 15
days. An improvement in pain, even if only partial, suggests
the participation of the continuous activation of Ad and C
fibers in the physiopathology of the syndrome. For that reason,
it is considered a positive response and strengthens the indication
for NRT in that specific case.
Furthermore, in those cases in which the indication for NRT
is questionable due to low pain intensity, the repeated application
of capsaicin may be a therapeutic option to consider.
Objectives.
-
To determine the validity of the capsaicin test in establishing
the indication and prognosis for NRT.
-
To define the degree of improvement in pain, measured
by points on the visual analog scale (VAS) that determines
the positive result of the test.
-
Additionally, to provide data to define pain intensity,
measured on a visual analog scale, under which the capsaicin
test could be a therapeutic option.
Methodology.
188 subjects took part in the study; all
had mechanical pathologies of the spine and were referred
from the National Health System to a Kovacs Back Unit to assess
the application of NRT and in whom there were no criteria
for carrying out urgent surgery. Patients with pain scoring
5 or more points on the visual analog scale and those in whom
other exceptional circumstances were found that could hinder
their follow-up (for example foreign patients who went to
the Unit expressly to be treated and could not easily return
periodically, etc.) were excluded. Patients excluded for any
reason were included in the record of exclusions. Prior surgery
of the spinal column was not a cause for exclusion.
All of the included subjects were prescribed the capsaicin
test (=day 1) on their first visit. Afterwards, their pain
was evaluated at 14 days (=day 15). That day concluded the
participation of those patients who were asymptomatic at that
time. Those who continued with pain between 0 and 2.9 points
on the VAS were prescribed capsaicin (if the test was positive)
and/or exercise (if indicated), but not NRT. Those who continued
having pain of 3 or more points on the VAS were given a NRT
intervention.
The patients' situation was appraised again 45 days later
(that is, 60 days after having started their participation
in the study).
The absence of subjective improvement of pain during the
first 15 days was considered a negative result of the capsaicin
test and subjective improvement of pain was considered a positive
result. In the analysis phase, the cut-off points of value
on the VAS were established in the controls of days 1 and
15 that defined the limit between positive and negative.
Among the patients who received NRT, two groups were established
according to their response to the capsaicin test. In both
groups, the percentage of patients who had improved after
the NRT was compared. Multiple linear regression models were
established to assess the influence of the test variables
in the association between "result of the capsaicin test"
and "result of NRT".
Participants, along with the Foundation's
Science Department.
Kovacs Back Units and the Clinical Biostatistics
Unit of the Hospital Ramón y Cajal.
Status.
The design phase has concluded and a source
of co-funding is being sought.
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