Quantitative sensory testing: a practical guide and clinical applications

Abstract

Learning objectivesBy reading this article, you should be able to:•Discuss the feasibility, use and limitations of quantitative sensory testing (QST) in clinical practice.•Specify the role of QST in research.•Perform QST in your own clinical practice after watching the training video and practising the protocol on healthy subjects.Key points•QST evaluates sensory processing in patients.•QST measures thresholds and levels of tolerance to a variety of standardised thermal and mechanical stimuli.•Conventional electrophysiology tests large, myelinated fibres, whereas QST assesses the entire somatosensory system, including small nerve fibres.•QST-based phenotyping supports prognostic research and evaluation of the efficacy of treatment in subgroups of patients.•In clinical practice, QST is used to diagnose small fibre neuropathies and monitor sensory deficits in other pain conditions over time. By reading this article, you should be able to:•Discuss the feasibility, use and limitations of quantitative sensory testing (QST) in clinical practice.•Specify the role of QST in research.•Perform QST in your own clinical practice after watching the training video and practising the protocol on healthy subjects. •QST evaluates sensory processing in patients.•QST measures thresholds and levels of tolerance to a variety of standardised thermal and mechanical stimuli.•Conventional electrophysiology tests large, myelinated fibres, whereas QST assesses the entire somatosensory system, including small nerve fibres.•QST-based phenotyping supports prognostic research and evaluation of the efficacy of treatment in subgroups of patients.•In clinical practice, QST is used to diagnose small fibre neuropathies and monitor sensory deficits in other pain conditions over time. Pain is a complex phenomenon with biological, social and psychological elements. The management of pain, especially chronic pain is challenging because of the large interpatient variability in response to analgesics, which results in high numbers needed to treat individual conditions. This variability in treatment response is likely to result from the heterogenous pathophysiological processes involved in the transition from acute pain to a chronic state (pain ‘chronification’). Peripheral and central sensitisation processes and reduced activity of central pain inhibitory pathways enhance nociception and influence the clinical phenotype. The variability in clinical phenotype is greater between patients than between different diagnostic categories, although disorder-specific profiles are also present.1Baron R. Förster M. Binder A. Subgrouping of patients with neuropathic pain according to pain-related sensory abnormalities: a first step to a stratified treatment approach.Lancet Neurol. 2012; 11: 999-1005Abstract Full Text Full Text PDF PubMed Scopus (217) Google Scholar Clinical pain phenotyping is therefore an important step to unravel whether the nature and intensity of the pain are modulated by peripheral and central processes. Pain treatments may be more effective when customised to measurable clinical phenotypes rather than being based on the diagnosis.2Edwards R.R. Schreiber K.L. Dworkin R.H. et al.Optimizing and accelerating the development of precision pain treatments for chronic pain: IMMPACT review and recommendations.J Pain. 2023; 24: 204-225Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar Quantitative sensory testing (QST) is a promising tool for pain phenotyping. QST represents a panel of clinical psychophysical tests that quantify somatosensory function by assessing the patient's sensory thresholds and tolerance of nerve fibres in skin or muscle tissue to a variety of standardised stimuli.3Rolke R. Baron R. Maier C. et al.Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): standardized protocol and reference values.Pain. 2006; 123: 231-243Abstract Full Text Full Text PDF PubMed Scopus (1916) Google Scholar Several studies have confirmed the usefulness of QST in research, for diagnosing, assessing and monitoring somatosensory deficits. The Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) and the Special Interest Group on Neuropathic Pain (NeuPSIG) consensus both recommend using QST for sensory profiling, to enhance treatment outcomes and improve the design of clinical trials.2Edwards R.R. Schreiber K.L. Dworkin R.H. et al.Optimizing and accelerating the development of precision pain treatments for chronic pain: IMMPACT review and recommendations.J Pain. 2023; 24: 204-225Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar,4Backonja M.M. Attal N. Baron R. et al.Value of quantitative sensory testing in neurological and pain disorders: NeuPSIG consensus.Pain. 2013; 154: 1807-1819Abstract Full Text Full Text PDF PubMed Scopus (421) Google Scholar However, QST has not yet been widely accepted into clinical practice. One of the reasons is that QST requires trained personnel to obtain high-quality data. Clinicians often do not know how to perform QST, interpret the results and are unaware of the usefulness of testing. This review outlines the clinical and research applications of QST, discusses the current evidence of its use, and includes training videos. These should enable clinicians to develop the knowledge and skills necessary for integrating QST into both clinical care and research. Quantitative sensory testing encompasses several psychophysical tests to assess the function of the somatosensory nervous system; the part of the sensory system concerned with vital (pain, temperature) and gnostic sensibility (fine touch, vibration and proprioception). By assessing these sensory qualities individually, QST provides insight into the function of large, myelinated Aβ, thinly myelinated Aδ and small unmyelinated C fibres and their corresponding central pathways. Quantitative sensory testing can quantify the severity of positive (e.g. hyperalgesia, allodynia) and negative phenomena (e.g. hypoaesthesia and hypoalgesia) (Figure 1).5Jensen T.S. Finnerup N.B. Allodynia and hyperalgesia in neuropathic pain: clinical manifestations and mechanisms.Lancet Neurol. 2014; 13: 924-935Abstract Full Text Full Text PDF PubMed Scopus (609) Google Scholar Quantitative sensory testing can be classified into two main categories: static and dynamic. In static QST, thresholds are assessed to determine the presence of hyper- or hypoalgesia. Dynamic QST focuses on the central mechanisms of pain processing by agitating the somatosensory system in a manner that exposes the specific mechanism of pain processing under assessment.6Arendt-Nielsen L. Yarnitsky D. Experimental and clinical applications of quantitative sensory testing applied to skin, muscles and viscera.J Pain. 2009; 10: 556-572Abstract Full Text Full Text PDF PubMed Scopus (429) Google Scholar Quantitative sensory testing includes many modalities to investigate different aspects of sensory and pain perception. This has resulted in a plethora of published protocols but only a few have been standardised. Many studies use the German Research Network on Neuropathic Pain (DFNS) testing protocol because of its high standardisation and reliability. This protocol consists of seven standardised tests measuring 13 variables that assess the functioning of somatosensory nerve fibres which are necessary for sensing pain, warmth and cold.3Rolke R. Baron R. Maier C. et al.Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): standardized protocol and reference values.Pain. 2006; 123: 231-243Abstract Full Text Full Text PDF PubMed Scopus (1916) Google Scholar,7Rolke R. Magerl W. Campbell K.A. et al.Quantitative sensory testing: a comprehensive protocol for clinical trials.Eur J Pain. 2006; 10: 77Crossref PubMed Scopus (1118) Google Scholar Before examination, the examiner and patient together determine the test site: the area where the most pain is felt, or where the most profound deficits based on standard examination are detected. Test site responses are compared with those of an unaffected control site, typically defined as the contralateral asymptomatic site. When bilateral symptoms or generalised sensory deficits are suspected, QST results are best interpreted when compared with published reference data specific for the body region tested. In the absence of normative reference data, it is suggested to use a control area in another body region than the affected region (e.g. hand vs foot).4Backonja M.M. Attal N. Baron R. et al.Value of quantitative sensory testing in neurological and pain disorders: NeuPSIG consensus.Pain. 2013; 154: 1807-1819Abstract Full Text Full Text PDF PubMed Scopus (421) Google Scholar During the examination, the patient lies on an examination table. The skin of both the test area and the control area is exposed to cold, warmth, touch with thin hairs (Von Frey monofilaments), calibrated pins, vibrations from a graded tuning fork and pressure at different intensities using a pressure algometer (Figure 2). The patient is asked to rate the intensity of the stimuli according to standardised instructions. It is essential to standardise all aspects when conducting QST. Therefore, stimuli are applied in prespecified intensity, duration, interstimulus interval and order. The accompanying videos show how the stimuli can be applied using standardised instructions based on the DFNS protocol (Figs 1–8 online videos). The following are the supplementary data related to this article:eyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiJmYTJiYjc1MmIzNGFiOGNmZTE0NjRiMWJhMjA0YWZlYSIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNzIzOTY3NzcyfQ.LZOdTBhYaUrX6bgXJijLmoMWvaPXUOvuk-KM3A81SVjHUvlFKZTZAdcYjlznDtHltSGsWzB75DecU8PghQw8eIZDySVo6APIkKapSEkYbwdiCtQmTJzFJsT_uv_-PPB_jo6Bvtb5hjgigAFC7TR4LgJrFDYqYeLNYfdUpaSim1kk12s_JLEnE9Fk0-5oXC1emKN7_QS38vDNYjD4T0Y_w1DyGq4VpudMt8sBZJct4vIBhNmdLbASsBZlMJSVyyFAhmgO6uvs54XPaB6WKBoOlIvQbj2Ek69F3O79mTYWCKvQehtoTMTig3K8HApsHnwsoTTyLv644BiQnVHBGF2P-A Download with Download with Download with Download with Download with Download with Download with Download with The design of the DFNS QST protocol includes comprehensive tests that measures of all of the somatosensory system somatosensory can be R. Magerl W. 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