Currently, there is still a lack of universal
understanding and formal definition of ‘pain
chronification’. This issue was addressed recently
by an international group of pain experts. 10
• Pain chronification describes the process of
transient pain progressing into persistent pain
• Pain processing changes as a result of an imbalance
between pain amplification and pain inhibition
• Genetic, environmental and biopsychosocial
factors determine the risk, degree and time-course
of chronification.
The key question: is chronic pain a symptom
or a disease?
Over the last two decades several pain specialists
called to recognise pain as a disease, whereas others
have argued against this concept. 11
In 2001, the European Pain Federation (EFIC ® )
claimed in their Declaration on pain that “chronic
and recurrent pain is a specific health care problem,
a disease in its own right.” 12 The concept that
chronic pain is considered to differ from pain as
a symptom remains a debated topic in the scientific
community.
To guide this debate, a pragmatic approach is to
start from the definitions of symptom and disease
respectively and to check if chronic pain fits into
the framework of these definitions.
According to the World Health Organization
(WHO), a disease is “a particular abnormal condition
that negatively affects the structure or function of
part or all of an organism, and that is not due to any
external injury....
A disease may be caused by external factors such
as pathogens or by internal dysfunctions. 13
Significant progress has been made over the last
20 years in unravelling neural mechanisms in the
central nervous system that are associated with
chronic pain. Substantial functional, structural and
chemical changes were demonstrated by advanced
neuroimaging studies, such as functional magnetic
resonance and PET scans. 14 Pain in these
circumstances is not simply a symptom of some
distinct disease pathology but rather the expression
of a pathologically functioning nervous system. 15
This means that chronic pain is “a particular
abnormal condition” and that both the “structure
and function of the organism” are negatively
affected. Moreover, chronic pain modifies not only
physical functioning, but also psychological and
social functioning.
A major step forward: the ICD-11
The International Classification of Diseases 11th
Revision (ICD-11) is the latest update of the global
standard for diagnostic health information. 16 In
2012, the IASP Task Force for the Classification of
FIGURE 1
Diagnostic criteria for chronic
primary pain
Conditions A–C are fulfilled:
A Chronic pain (persistent or recurrent for longer
than 3 months) is present
B The pain is associated with at least one of the
following:
B.1 Emotional distress due to pain is present.
B.2 The pain interferes with daily life activities and
social participation.
C The pain is not better accounted for by another
chronic pain condition.
4 | 2019 | hospitalpharmacyeurope.com
Chronic Pain developed a new classification of
chronic pain, published the proposals and
commenced intensive field testing.
The ICD-11 was approved on 25 May 2019 and
it will come into effect on 1 January 2022.
For the first time, the ICD-11 includes seven
diagnostic categories of chronic pain. Importantly,
one of these categories, termed chronic primary
pain (MG30.0), acknowledges chronic pain as
a health condition in its own right.
In addition, six forms of chronic secondary
pain (MG30.1-MG30.6), describe chronic pain that
developed as a symptom in the context of an
underlying disease such as cancer and rheumatoid
arthritis among others.
The inclusion of chronic pain in this classification
is characterised by clearly operationalised diagnostic
criteria and precise definition for each chronic pain
diagnosis. Additionally, the different levels of
diagnostic detail enable the use of the ICD-11 in
a variety of settings, from primary to tertiary care.
As discussed above, chronic pain modifies not only
physical functioning, but also psychological and
social functioning. Notably, the coding of pain and
pain-associated disability should be harmonised
between ICD-11 and the International Code of
Functioning (ICF). 17 This harmonisation would be
highly relevant for chronic pain. 18
What is chronic primary pain?
ICD-11 has introduced new diagnostic criteria
for the coding of chronic pain (see Figure 1).
Whereas the diagnostic criteria of chronic
secondary pain are mostly straightforward,
diagnosing chronic primary pain is more
challenging. 19
Chronic primary pain is multifactoral, involving
biological, psychological and social factors. The
diagnosis is appropriate independently of identified
biological or psychological contributors unless
another diagnosis would better account for the
presenting symptoms. Other chronic pain diagnoses
to be considered are:
• Chronic cancer-related pain
• Chronic post-surgical/post-traumatic pain
• Chronic neuropathic pain
• Chronic secondary headache/orofacial pain
• Chronic secondary visceral pain, and
• Chronic secondary musculoskeletal pain. 20
Impact of pain
In addition to serious consequences on the patient’s
life, chronic pain has severe and profound effects on
their social and family environment. Coupled with
this, at the societal level, chronic pain leads to
frequent use of healthcare and welfare resources,
and is one of the leading causes of absence from
work. These factors generate a substantial
socioeconomic burden derived from both direct and
indirect costs (including loss of productivity,
compensation payments as a result of the patient’s
disability).
The experience of pain negatively impacts many
aspects of a patient’s life (Table 1). 21
It has been shown that non-cancer chronic pain
affects between 10% and 30% of the population
across Europe. 22
Effect on the patient and quality of life
Chronic pain correlates with reduced physical
activity and even disability. 21 Bassols et al 23 showed
that in individuals with chronic back pain, only
approximately 32% were able to perform daily
activities.
TABLE 1
Negative
impact of
chronic pain
Psychological
• Depression
• Sleep disturbances
• Anxiety
• Ability to cope
• Fear
Social
• Social interactions/
network
• Family
• Work
Quality of life
• Mental health
• Social functioning
• Physical functioning
• Impact on general
daily activities