Quantitative sensory testing

Quantitative sensory testing (QST) is a panel of diagnostic tests used to assess somatosensory function, in the context of research and as a supplemental tool in the diagnosis of somatosensory disorders, including pain insensitivity, painless and painful neuropathy. The panel of tests examine a broad range of different sensations, including hot, cold, touch, vibration. It has both positive and negative tests (can test for increased or reduced sensitivity). QST reflects a formalisation of existing neurological tests into a standardised battery designed to detect subtle changes in sensory function. Large datasets representing normal responses to sensory tests have been established to quantitate deviation from the mean and allow comparison with normal patients. It is thought that a detailed evaluation of somatosensory function may be useful in identifying subtypes of pain and as a potential tool to identify asymptomatic neuropathy, which may represent up to 50% of total people with neuropathy (or loss of the nerve fibres). In clinical use, it is often combined with other tests such as clinical electrophysiology. In research settings it is increasingly applied in combination with advanced imaging such as fMRI, epidermis "nerve" biopsies and microneurography to classify subtypes of painful disorders. The Neuropathic Pain Special Interest Group (NeuPSIG) of the International Association for the Study of Pain (IASP) have recommended the clinical use of QST in the diagnosis and evaluation of patients with small and large fibre neuropathy as well as screening for deficits of the somatosensory system (which may include deficits in the brain for instance). The group also recommend that the technique not be used in patients in litigation, or with severe learning or cognitive deficits as it is likely to be inaccurate due to its psychophysical basis. The recommendations are based on large trials suggesting inter-test reliability of the method. Standard parameters are evaluated using calibrated testing apparatus.