Patients with probable (presence of a combination of symptoms and signs of neuropathy include any two or more of the following: neuropathic symptoms, decreased distal sensation, or unequivocally decreased or absent ankle reflexes) or confirmed (presence of an abnormality of NC or validated measure of small fiber neuropathy with class 1 evidence with corresponding symptoms) neuropathy are included. Patients are then further divided into those with painful and painless neuropathy according to the NeuPSIG algorithm. Patients with probable or definite neuropathic pain are classified as painful neuropathy, those with unlikely neuropathic pain classified as painless neuropathy (with concomitant nociceptive pain of other origin, e.g. headache etc.). Patients with possible neuropathic pain are excluded from analysis as are patients with skin lesions or dermatological disorders in the areas to be tested upon QST, with any painful or neurological comorbidity that could otherwise influence testing results such as vascular disease, radiculopathy, spinal canal stenosis etc. Inclusion was restricted to patients with polyneuropathy to make the investigated patient sample as homogenous as possible.~Age, gender, BMI, ethnicity, years in education, family history of chronic pain, etiology of neuropathy, presence of early traumatic events and hospital admissions, smoking and alcohol habits, pain characteristics (von Korff, BPSI, NPSI), emotional well-being (PROMIS depression/ anxiety), personality (TIPI, IPIP, PCS), severity of neuropathy are assessed and QST performed.
Patients with neuropathic pain of multiple etiologies and a control cohort of patients with the same neuropathic entities who did not develop neuropathic pain are examined clinically, phenotyped with QST and questionnaires. Both groups are analyzed in order to find risk factors for painful neuropathy.