How is complex regional pain syndrome not otherwise specified (CRPS-NOS) defined?

Updated: Jun 20, 2018
  • Author: Gaurav Gupta, MD; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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In 2003, a closed workshop was held in Budapest, Hungary to study and resolve this matter. Experts in CRPS published the results of this workshop in a 2007 review article [5] showing that the modified criteria, mentioned above, produced better discrimination between CRPS and non-CRPS neuropathic pain, yielding better diagnostic accuracy than the original unmodified criteria. [5]

The study results indicated that when 2 of 4 sign categories were present and 3 of 4 symptom categories were present, the resultant sensitivity was 0.85 and the specificity was 0.69 for a clinical diagnosis of CRPS. This appeared to be a good compromise between identifying as many patients as possible in the clinical context and substantially reducing the high level of false-positive diagnoses associated with the 1994 IASP criteria. However, a higher specificity is required to meet research criteria, so the committee recommended that 2 of the 4 sign categories and all 4 symptom categories must be positive for the diagnosis to be made in a research setting, resulting in a sensitivity of 0.70 and specificity of 0.94.

Due to the combination of increased specificity and reduced sensitivity, about 15% of patients previously diagnosed with CRPS were considered "without a diagnosis." Therefore, a third diagnostic subtype, complex regional pain syndrome not otherwise specified (CRPS-NOS), was recommended to categorize those patients. [6] These new IASP diagnostic criteria have been submitted to the medical committee for Classification of Chronic Pain of the IASP for future revision of formal taxonomy and diagnostic criteria. 

The criteria are given here in hopes that higher specificity for the identification of CRPS will enhance research into the pathoetiology of this disorder without creating a reduced, or even harmful, rate of clinical diagnosis that could deny affected patients access to treatment. In addition, these criteria may result in more cost-effective approaches for the management of this disorder. [5, 7, 6]  These criteria, as listed below, are given in the most current version of the IASP's Complex regional pain syndrome: practical diagnostic and treatment guidelines (4th edition) [8]  where they are described as "state of the art" diagnostic criteria and "practical" guidelines.

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