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BACKGROUND: Central sensitization cannot be demonstrated directly in humans. Therefore, studies used different proxy markers (signs, symptoms and tools) to identify factors assumed to relate to central sensitization in humans, that is, Human Assumed Central Sensitization (HACS). The aims of this systematic review were to identify non-invasive objective markers of HACS and the instruments to assess these markers in patients with fibromyalgia (FM). METHODS: A systematic review was conducted with the following inclusion criteria: (1) adults, (2) diagnosed with FM, and (3) markers and instruments for HACS had to be non-invasive. Data were subsequently extracted, and studies were assessed for risk of bias using the quality assessment tools developed by the National Institute of Health. RESULTS: 78 studies (n = 5234 participants) were included and the findings were categorized in markers identified to assess peripheral and central manifestations of HACS. The identified markers for peripheral manifestations of HACS, with at least moderate evidence, were pain after-sensation decline rates, mechanical pain thresholds, pressure pain threshold, sound 'pressure' pain threshold, cutaneous silent period, slowly repeated evoked pain sensitization and nociceptive flexion reflex threshold. The identified markers for central manifestations of HACS were efficacy of conditioned pain modulation with pressure pain conditioning and brain perfusion analysis. Instruments to assess these markers are: pin-prick stimulators, cuff-algometry, repetitive pressure stimulation using a pressure algometer, sound, electrodes and neuroimaging techniques. CONCLUSIONS: This review provides an overview of non-invasive markers and instruments for the assessment of HACS in patients with FM. Implementing these findings into clinical settings may help to identify HACS in patients with FM. [ABSTRACT FROM AUTHOR]

Background: The assessment of a neuropathic pain component (NePC) to establish the neurological criteria required to comply with the clinical description is based on history taking, clinical examination, and quantitative sensory testing (QST) and includes bedside examination (BSE). The objective of this study was to assess the potential association between the clinically diagnosed presence or absence of an NePC, BSE, and the Nijmegen–Aalborg screening QST (NASQ) paradigm in patients with chronic (≥3 months) low back and leg pain or with neck shoulder arm pain or in patients with chronic pain due to suspected peripheral nerve damage.Methods: A total of 291 patients participated in the study. Pain (absence or presence of neuropathic pain) was assessed independently by two physicians and compared with BSE (measurements of touch [finger, brush], heat, cold, pricking [safety pin, von Frey hair], and vibration). The NASQ paradigm (pressure algometry, electrical pain thresholds, and conditioned pain modulation) was assessed in 58 patients to generate new insights.Results: BSE revealed a low association of differences between patients with either absent or present NePC: heat, cold, and pricking sensations with a von Frey hair were statistically significantly less common in patients with present NePC. NASQ did not reveal any differences between patients with and without an NePC.Conclusion: Currently, a standardized BSE appears to be more useful than the NASQ paradigm when distinguishing between patients with and without an NePC. [ABSTRACT FROM AUTHOR]