“How shall I put it?”
Authors:   , den Boer Catharina 
Published: September 2023

Summary
In the general introduction in chapter 1, we describe the background of the research and the research questions we have studied.

Persistent physical symptoms (PPS) are one or more physical symptoms that last at least weeks and cause dysfunction or significant distress. The physical symptoms may occur in the context of an (adequately treated) medical condition or in the absence of a medical condition.
Central sensitization (CS) is a hypersensitivity of the central nervous system to sensory stimuli. In CS, these stimuli are amplified due to an increase in receptors and neurotransmitters in the dorsal horn of the spinal cord.

We investigated whether CS can serve as a useful explanatory model for GPs and patients with PPS, and whether the addition of a test makes the explanation more acceptable and clear.

In Chapter 2 we report on our systematic review of the literature regarding definitions, operationalisations and mechanisms of CS in chronic pain and persistent physical symptoms research. The most mentioned theme in the definitions of CS was the hyperexcitability of the central nervous system. We found eight different operationalisations. CS is most frequently measured with various forms of quantitative sensory testing (QST), (f)MRI, laboratory evaluation of neurotransmitters and questionnaires.

In chapter 3 we report the results of our Delphi study for tests for CS in general practice. In this study we aimed to assess which tests might have added value compared with providing only an explanation and which might be feasible and thus be suitable for use in general practice.

In two rounds, the panellists reached a consensus on 14 of the 15 tests: 3 were included, and 11 were excluded. In the first round we included the Central Sensitisation Inventory (CSI) and in the second round the algometer to measure pressure pain thresholds (PPTs). In the second round we also selected the monofilament to measure temporal summation, because the score of the panellists of 69% was close to the threshold value of 70%.

In Chapter 4 we describe our focus group study of the experiences of GPs explaining CS to patients with PPS. GPs reported that they have to be convinced that they are dealing with PPS to provide a persuading explanation to the patient. They stressed that it is essential to show empathy and to coach the patient. Most patients understood the CS model, according to GPs, and accepted that it might explain their symptoms’ persistence.

In chapter 5, we present the findings of the part of our study in which we investigated the experiences of GPs and patients with explaining and testing CS. The GPs used the Central Sensitisation Inventory (CSI), an algometer for testing pressure pain thresholds (PPTs), and a monofilament for testing temporal summation. The results of the CSI confirmed CS-related symptoms more often (74%) than the algometer (46%) and monofilament (43%), and many GPs preferred the CSI. Patients did not have a preference for a particular test, but found the tests meaningful and the CS explanation clearer when a test was used.

Chapter 6 synthesises our main findings and compares these with the existing literature. Additionally, we discuss the strengths and limitations of our methodology. Finally, we provide recommendations for clinical practice, further research, medical education, and a conclusion.
We found that, with a short training, GPs were able to explain CS to their patients. GPs reported that the explanation with CS was understandable and acceptable for their patients. Therefore, we recommend that GPs should be encouraged to provide their patients with an explanation of CS if the patient is open to it.