The cross-sectional validity of three measurement instruments for central sensitization

Many patients with chronic pain show features of central sensitization. Central
sensitization, characterized by generalized hypersensitivity of
the somatosensory system, is due to a dominance of the facilitatory system over
the inhibitory system. The presence of central sensitisation is a negative
prognositc factor and might be an indication of a poor response to physical
therapies. Currently, an international consensus definition
or clinical criteria for central sensitization is essentially lacking.

The primary aim of the study is to establish the cross-sectional validity of
three different measurement instruments for central sensitization, including
the Dutch Central Sensitization Inventory and two test to measure pain
inhibition: heterotopic noxious conditioning stimulation test and a submaximal
exercise test
The secondary aim is to compare the results on the three different measurement
instruments for central sensitizationtest between persons with fibromyalgia and
persons without complaints.
The tertiare aim is to establish the optimal cutoff pont for the Central
Sensitization Inventory to identify persons with central sensitization.

All patients will sign an informed consent. In one session the patient will
complete the Dutch Central Sensitization Inventory and two tests, a heterotopic
noxious conditioning stimulation test and a submaximal exercise test. Before
the tests pain pressure thresholds (PPT) will be measured at three different
sites; on the proximal third of the calf, at the upper trapezius muscle (pars
descendens) midway between the seventh cervical vertebra and the tip of the
acromion, and on the middle dorsal side of the third digit. The subject need to
indicate when the pressure is starting to feel painfull. At that moment, the
achieved pressure in kilogram/cm2 (kg/cm2) will be noted as the PPT. Each
measurement will be conducted twice on both the left and right side. Of these 2
measurements per site a mean value will be calculated. PPT will be measured
with a manual analog Fisher algometer (Force Dial model FDK, Wagner
Instruments).
The heterotopic noxious conditioning stimulation test: The participant sit on
a chair. The non-dominant hand is submersed up to 10cm above the wrist in hot
noxious water (45,5°C) for 6 minutes. After 2 minutes of submersion of the
hand, PPTs are measured at the three different sites of the dominant side. Two
minutes after the conditioning stimulus is removed, PPT measurements are
performed again on the dominant side.
The submaximal exercise test: For this test we use the Aerobic Power Index
Test. This test is performed on a bicycle ergometer, starting at 25 Watt. After
5 min. warming-up the resistance is gradually increased by 25 Watt/minute until
75% of the age predicted maximal heart rate (220 minus age) is achieved.Two
minutes after the test, PPT measurements are performed again on 3 sites of the
dominant and non-dominant side (6 locations).
The order of the tests will be allocated by randomisation for each participant.

Patients who are central sensitizied can show signs of dizziness, headache,
fatigue or nausea due to the test protocol. However, the protocol ensures that
the duration of the tests will be kept low (<10 minutes), thus avoiding extreme
fatigue or deregulation of the autonome system. Besides, test can be cancelled
at any time by the researcher or patient. Therefore, we do not expect severe
complaints due to the test protocol or complaints lasting longer than 24 hour.
The level of pain, nausea and dizziness will be recorded before the two tests,
for every patient.