Diagnostic Methods for Neuropathic Pain: A Review of Diagnostic Accuracy [Internet]

Excerpt

Compared to nociceptive or inflammatory pain, individuals with neuropathic pain (NP) suffer from more severe disease, greater costs, and relatively reduced health related quality of life. Direct and indirect costs of NP represent a substantial economic burden on the Canadian healthcare system with per patient costs estimated at $2567 (± $2711) per three month care period. Neuropathic pain is defined by the International Association for the Study of Pain (IASP) as “pain arising as a direct consequence of a lesion or disease affecting the somatosensory system”. The etiology of NP is broad and associated conditions (e.g., cancer, surgery, diabetes, herpes zoster) have been classified into four distinct categories: peripheral nervous system focal and multifocal legions (e.g., post-herpetic neuralgia); peripheral nervous system generalized polyneuropathies (e.g., diabetic neuropathy); central nervous system lesions (e.g., spinal cord injury); and, complex neuropathic disorders including complex regional pain syndrome types I and II. While rates of NP-associated conditions are well documented, rates of NP in the general population are difficult to quantify and under-diagnosed. Studies in the United Kingdom and France that utilized screening tools to identify NP have estimated that 6–8% of patients with chronic pain experience NP in the general population. A single Canadian study that used telephone-based questionnaires for determining NP rates estimated a higher (18%) rate in the general population. Limitations and lack of standardization of diagnostic methods increase the potential for undetected or poorly classified cases. There is no recognized objective gold standard for assessing NP. However, the Special Interest Group on Neuropathic Pain (NeuPSIG) of the IASP has set out a grading system that has been used to guide clinical assessment and diagnosis. This approach involves multiple steps including obtaining a clinical history of pain, assessing the neuroanatomical plausibility of pain, using sensory assessments to confirm nervous system involvement, and running diagnostic tests to confirm nervous system lesions or disease. Other less resource intensive methods of diagnosis have been documented and may be especially useful in primary care. These strategies include, but are not limited to NP screening tools such as: the Douleur Neuropathique 4 (DN4), PainDETECT (PD-Q) the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS), and the standardized evaluation of pain (StEP). Screening tools are comprised of an interview component and, in some cases, the addition of a brief bedside clinical assessment. Many of these tools have been translated for application in other languages and populations. Given observed variation in the approach to diagnosis of NP and the significant disease burden, it is of interest to assess the diagnostic accuracy of methods of assessing NP. Improved diagnostic procedures may facilitate improvements in treatment approaches.