International Association For The Study Of Pain Criteria Research Articles

Post-fracture serum cytokine levels are not associated with a later diagnosis of complex regional pain syndrome: a case-control study nested in a prospective cohort study

BackgroundComplex Regional Pain Syndrome (CRPS) is a disabling pain disorder that is most common after a distal limb fracture. While the acute systemic immune response to the injury is thought to play a role in the development of CRPS, this hypothesis has never been tested directly. Thus, we evaluated whether elevated levels of circulating pro-inflammatory cytokines early after a fracture were associated with the development of CRPS.MethodsWe conducted a case-control study nested within a prospective cohort study. Individuals with wrist and/or hand fractures were recruited from specialist hand units. Baseline clinical data were obtained from participants within 28 days of fracture. CRPS status was determined 16 weeks after the fracture using a two-stage diagnostic process. Cytokine assays were obtained from all cases (defined using the Budapest criteria) and a random sample of those who did not have CRPS at 16 weeks. We calculated odds ratios with 95% confidence intervals to determine the risk of CRPS associated with the expression of each of 25 cytokines.ResultsBaseline data were collected for 702 consenting participants, of whom 535 provided blood samples. Follow-up at 16 weeks was 97.2%. 15 (2.2% of the cohort) met the Budapest CRPS criteria and 69 (including those who met the Budapest criteria; 9.8%) met the International Association for the Study of Pain (IASP) CRPS criteria. In all of the primary analyses (using Budapest criteria) and 49/50 secondary analyses (using IASP criteria), 95% confidence intervals for the association between cytokine levels and the risk of subsequently developing CRPS included the null value (OR = 1). However, the confidence intervals were wide.ConclusionThere was no evidence that early post-injury expression of systemic cytokines was associated with a CRPS diagnosis 16 weeks after injury. This study does not provide support for the hypothesis that innate immune activation has a determinative role in the development of CRPS.

Nociplastic Pain Criteria or Recognition of Central Sensitization? Pain Phenotyping in the Past, Present and Future.

Recently, the International Association for the Study of Pain (IASP) released clinical criteria and a grading system for nociplastic pain affecting the musculoskeletal system. These criteria replaced the 2014 clinical criteria for predominant central sensitization (CS) pain and accounted for clinicians’ need to identify (early) and correctly classify patients having chronic pain according to the pain phenotype. Still, clinicians and researchers can become confused by the multitude of terms and the variety of clinical criteria available. Therefore, this paper aims at (1) providing an overview of what preceded the IASP criteria for nociplastic pain (‘the past’); (2) explaining the new IASP criteria for nociplastic pain in comparison with the 2014 clinical criteria for predominant CS pain (‘the present’); and (3) highlighting key areas for future implementation and research work in this area (‘the future’). It is explained that the 2021 IASP clinical criteria for nociplastic pain are in line with the 2014 clinical criteria for predominant CS pain but are more robust, comprehensive, better developed and hold more potential. Therefore, the 2021 IASP clinical criteria for nociplastic pain are important steps towards precision pain medicine, yet studies examining the clinimetric and psychometric properties of the criteria are urgently needed.

Validity of the Budapest Criteria For Poststroke Complex Regional Pain Syndrome.

Complex regional pain syndrome-1 is a chronic neuropathic disorder, and poststroke complex regional pain syndrome (PS-CRPS) is not a rare complication. There is a lack of study implementing the Budapest criteria for PS-CRPS diagnosis. Thus, the present study investigated the validity of the Budapest criteria for PS-CRPS diagnosis and assessed the PS-CRPS-related factors in stroke patients with an affected upper extremity. The study included 72 patients with first-ever stroke resulting in hemiplegia. The prevalence of PS-CRPS and diagnostic validity were compared among the Budapest clinical criteria, Budapest research criteria, modified Budapest criteria (removal of the motor factor from the motor/trophic category), and International Association for the Study of Pain (IASP) criteria in patients diagnosed with PS-CRPS according to the Budapest clinical criteria. PS-CRPS was diagnosed in 6 (8.3%), 1 (1.4%), 6 (8.3%), and 11 patients (15.3%) according to the Budapest clinical criteria, Budapest research criteria, modified Budapest criteria, and IASP criteria, respectively. The Budapest criteria and IASP criteria had sensitivities of 0.99 and 1.00, respectively, and specificities of 0.68 and 0.41, respectively, for PS-CRPS diagnosis. There were no differences in risk factors between PS-CRPS patients and non-PS-CRPS patients when the diagnosis was based on the Budapest clinical criteria. However, there were differences in muscle strength and Brunnstrom stage between PS-CRPS patients and non-PS-CRPS patients when the diagnosis was based on the IASP criteria. Our findings indicate that the diagnostic validity of the current Budapest clinical criteria for PS-CRPS is low. Thus, the current Budapest criteria might not be appropriate for PS-CRPS diagnosis.

Multicenter study on the asymmetry of skin temperature in complex regional pain syndrome: An examination of temperature distribution and symptom duration.

According to the International Association for the Study of Pain (IASP) and American Medical Association (AMA), the diagnostic criteria for complex regional pain syndrome (CRPS) require the presence of skin temperature asymmetry. In CRPS, it is generally accepted that the temperature of skin of affected limbs changes from warm to cold; however, in our clinical practice, we have experienced many cases with different thermographic characteristics. Therefore, we conducted a retrospective multicenter study that examined the distribution of skin temperature in patients with CRPS and skin temperature asymmetry versus symptom duration.Patients diagnosed with type 1 or 2 CRPS were recruited. After confirming CRPS according to the IASP diagnostic criteria, infrared thermographic images were evaluated for skin temperature differences (ΔT) between the affected and unaffected limbs.A total of 296 patients with CRPS were included in this study. The median duration of symptoms was 6 months and the mean ± standard deviation of ΔT was –0.72 ± 1.65°C. A skin temperature difference between bilateral limbs (|ΔT|) of 1°C or less was seen in 131 patients (44.3%); thus, these 131 patients did not meet the IASP criteria for CRPS. Further, cool skin temperature was not observed in 88 patients (29.7%), meaning that these patients did not meet the AMA criteria for CRPS. There was no correlation between the symptom duration and ΔT (Spearman's rho = –0.075, P = 0.196) and there was no significant difference in the average ΔT among the 4 symptom duration groups (0–3 months, 4–6 months, 7–12 months, >12 months, P = 0.08).In conclusion, a considerable proportion of the patients that participated in this study did not meet the thermal criteria set forth by the IASP and AMA. Further, there was no correlation between symptom duration and skin temperature difference.

Complex Regional Pain Syndrome Caused by Lumbar Herniated Intervertebral Disc Disease

Most cases of complex regional pain syndrome (CRPS) occur after some inciting injury. There are a few cases of CRPS after an operation for disc disease. CRPS from a mild herniated intervertebral disc (HIVD) without surgical intervention is even rarer than CRPS after an operation for disc disease. A 22-year-old man was transferred to a pain clinic. He had continuously complained about back and right leg pain. He presented with a skin color change in the right lower leg, intermittent resting tremor, stiffness, and swelling in the right leg. He complained of a pulling sensation and numbness in his right buttock, posterior thigh, lateral calf, and ankle. This symptom was in accordance with L4/5 radiculopathy. Magnetic resonance imaging (MRI) also showed L4/5 HIVD that was central to the bilateral subarticular protrusion. He was diagnosed as having CRPS, which fits the revised International Association for the Study of Pain (IASP) criteria. He fulfilled 4 symptom categories (allodynia, temperature asymmetry and skin color change, sweating changes, decreased range of motion and motor dysfunction) and 3 of 4 sign categories (allodynia, temperature asymmetry and skin color changes, decreased range of motion and motor dysfunction). The bone scan and thermography also revealed CRPS. For the past 2 months, we have performed intensive treatments. But, he never became painfree and walking for 5 minutes led to persistent leg pain. We decided to perform percutaneous nucleoplasty, which can directly decompress a HIVD. On the next day, he achieved dramatic symptom relief. The visual analog scale (VAS) score improved to 3, compared to the VAS score of 9 at the first visit. The skin color change, allodynia, and tremor in the right leg disappeared, and the temperature asymmetry normalized. Motor weakness of the right leg also recovered. We report an unusual case of CRPS that was caused by L4/5 HIVD without a history of trauma or surgery. It has a clear causal relationship between HIVD and CRPS and definitively fits in the newly revised IASP criteria. In conclusion, mild HIVD can cause CRPS without any trauma. And percutaneous nucleoplasty can be considered as a treatment option. Key words: Complex regional pain syndrome, diagnosis, herniated intervertebral disc, nucleoplasty, radiculopathy, sign, symptom, treatment

Complex regional pain syndrome: recent updates

Complex regional pain syndrome (CRPS) may be defined as a painful and disabling disorder affecting one or more extremities showing signs of vasomotor (relating to the constriction and dilatation of blood vessels), sudomotor (stimulation of sweat glands), inflammatory, and trophic changes (changes brought about in tissues from interruption or destruction of nerve, blood supply or both) in the affected extremity. CRPS can occur after even trivial injury and, on occasion, can develop spontaneously. It was first described as a spectrum of symptoms during the American Civil War by Silas Weir Mitchell and colleagues in their book entitled Gunshot Wounds and Other Injuries of Nerves, and named it causalgia. The gamut of symptoms stretches from a self-limiting mild condition to a severe, debilitating condition affecting the quality of life and having a high impact on activity. Owing to the varied manifestation, the patient can present to any specialty be it orthopaedics, rheumatology, neurology, dermatology, or pain medicine. Pain is an early presenting feature and can be the most prominent of symptoms. A high index of suspicion is needed as early diagnosis and treatment may prevent the progression of symptoms and prevent disability. It has been known by many names in the past, including reflex sympathetic dystrophy, algodystrophy, algoneurodystrophy, Sudeck’s dystrophy, and causalgia. In 1994, the International Association for the Study of Pain (IASP) came up with a standardized set of criteria to diagnose CRPS. Until then, numerous different diagnostic and clinical criteria were used. As IASP criteria lacked specificity, a new set of diagnostic criteria were adapted at a closed conference of leading experts from around the world in the Fall of 2004 in Budapest, Hungary—these were called the ‘Budapest criteria’ (Table 1). The Budapest criteria were compared with the former IASP criteria and found to have a higher specificity while maintaining sensitivity, and were validated. Clinical presentation

Development of comprehensive diagnostic criteria for complex regional pain syndrome in the Japanese population

Complex regional pain syndrome (CRPS) is a syndrome that describes a broad spectrum of sensory, motor and autonomic-like features with unproven etiology. The International Association for the Study of Pain (IASP) diagnostic criteria of CRPS shows high sensitivity but poor specificity. Using statistical-pattern-recognition methods, American researchers have suggested a new set of criteria offering acceptable sensitivity and high specificity. However, non-American CRPS patients present distinct subsets of CRPS-related signs/symptoms from those of American patients. Here, we followed a series of American studies to develop a set of CRPS diagnostic criteria that would be most suitable for the Japanese population. A standardized sign/symptom checklist was used in patient evaluations to obtain data on CRPS-related signs/symptoms in 195 participants meeting the IASP criteria. Using factor analysis, we grouped CRPS-related signs/symptoms into five distinct subgroups (trophic change, motor dysfunction, abnormal pain processing, asymmetric sudomotor activity and asymmetric edema). Discriminant function analysis of these subgroups, regarding their ability to discriminate between CRPS and non-CRPS etiology, indicated that modifying the IASP criteria could increase clinical diagnostic accuracy in the Japanese population. Our diagnostic criteria are not exactly the same as the American criteria, indicating a need for more regionally based CRPS diagnostic criteria. Different sets of CRPS diagnostic criteria could lead to dissimilar patients being diagnosed as CRPS, however, presenting problems for translation of therapeutic effects found in various studies. Therefore, we further recognize a need for a global set of common CRPS diagnostic criteria.

Outcome of the Complex Regional Pain Syndrome

The outcome of complex regional pain syndrome (CRPS) is relatively unknown. High disease resolution rates have been reported, but also long-lasting impairments in many patients. This study aims to assess CRPS outcome in a population-based cohort of CRPS patients. CRPS patients were retrospectively identified (1996 to 2005) in a Dutch general practitioners database, the integrated primary care information project, and included if at onset (ie, in the past) they had complied with the International Association for the Study of Pain (IASP) diagnostic criteria. The disease status at minimum of 2 years since onset was assessed during visits using questionnaires, interviews, and physical examination. Symptoms and signs were compared with reference patients with an identical past injury but without CRPS. Actual fulfillment of the IASP criteria, treatment status, self-reported recovery, and working status were recorded. Moreover, to identify the potential prognostic factors, baseline patient characteristics were compared across subgroups according to the CRPS outcome. These subgroups were derived by cluster analysis on actual symptoms and signs. One hundred and two CRPS patients were assessed at on average 5.8 years (range: 2.1 to 10.8) since onset. CRPS patients displayed higher symptom and sign prevalences in all categories (sensory, vasomotor, sudomotor, and motor/trophic) than controls. Sixteen percent (95% CI: 9-22) reported the CRPS as still progressive, whereas 31% (95% CI: 19-43) were incapable of working. Patients in the poorest outcome cluster more often had their upper extremity affected, event other than a fracture, and cold CRPS. Severe CRPS outcome is rare, but a majority of patients has persistent impairments at 2 or more years since onset.

Systematic Review of Lumbar Discography as a Diagnostic Test for Chronic Low Back Pain

The intervertebral disc has been implicated as an etiology of chronic lumbar spine pain based on clinical, basic science, and epidemiological research. However, there is lack of consensus regarding the diagnosis and treatment of intervertebral disc disorders. Based on controlled evaluations, the lumbar intervertebral discs have been shown to be sources of chronic back pain without disc herniation in 26% to 39%. Lumbar provocation discography, which includes disc stimulation and morphological evaluation, is often used to distinguish a painful disc from other potential sources of pain. Despite the extensive literature, controversy continues about provocation lumbar discography. A systematic review of the lumbar provocation discography literature. To systematically assess the diagnostic accuracy of lumbar discography. A systematic review of the literature was performed to assess the diagnostic accuracy of lumbar discography with respect to chronic low back pain. Study inclusion/exclusion criteria were based on International Association for the Study of Pain (IASP) standards with pain provocation and determination of controlled discs. Selected studies were then subjected to a rating instrument for diagnostic accuracy studies. Specific data were then culled from these studies and tabulated. Quality of evidence was assessed using modified Agency for Healthcare Research and Quality (AHRQ) diagnostic accuracy evaluation. Studies meeting methodologic quality criteria scores of 50 or higher were included in the assessment of the level of evidence. Qualitative analysis was conducted using 5 levels of evidence, ranging from Level I to III, with 3 subcategories in Level II. The rating scheme was modified to evaluate the diagnostic accuracy. Based on a modified U.S. Preventive Services Task Force (USPSTF) level of evidence criteria, this systematic review indicates the strength of evidence as Level II-2 for the diagnostic accuracy of lumbar provocation discography utilizing IASP criteria. Limitations include a paucity of literature, poor methodologic quality, and very few studies performed utilizing IASP criteria. Based on the current systematic review, lumbar provocation discography performed according to the IASP criteria with control disc (s) with minimum pain intensity of 7 of 10, or at least 70% reproduction of worst pain (i.e. worst spontaneous pain of 7 = 7 x 70% = 5) may be a useful tool for evaluating chronic lumbar discogenic pain. Discography is an important imaging and pain evaluation tool in identifying a subset of patients with chronic low back pain secondary to intervertebral disc disorders.

Systematic Review of Cervical Discography as a Diagnostic Test for Chronic Spinal Pain

Background: Chronic neck pain represents a significant public health problem. Despite high prevalence rates, there is a lack of consensus regarding the causes or treatments for this condition. Based on controlled evaluations, the cervical intervertebral discs, facet joints, and atlantoaxial joints have all been implicated as pain generators. Cervical provocation discography, which includes disc stimulation and morphological evaluation, is often used to distinguish a painful disc from other potential sources of pain. Yet in the absence of validation and controlled outcome studies, the procedure remains mired in controversy. Study Design: A systematic review of the cervical discography literature. Objective: To evaluate the validity and usefulness of cervical provocation discography in managing and diagnosing discogenic pain by means of a systematic review. Methods: Following a comprehensive search of the literature, selected studies were subjected to a modified Agency for Healthcare Research and Quality (AHRQ) diagnostic accuracy evaluation. Qualitative analysis was conducted using 5 levels of evidence, ranging from Level I to III with 3 subcategories in Level II. The rating scheme was modified to evaluate the diagnostic accuracy. Results: A systematic review of the literature demonstrated that cervical discography plays a significant role in selecting surgical candidates and improving outcomes, despite concerns regarding the false-positive rate, lack of standardization, and assorted potential confounding factors. Based on the studies utilizing the International Association for the Study of Pain (IASP) criteria, the data show a prevalence rate ranging between 16% and 20%. Based on the 3 studies that utilized IASP criteria during the performance of cervical discography, the evidence derived from studies evaluating the diagnostic validity of the procedure, the indicated level of evidence is Level II-2 based on modified U.S. Preventive Services Task Force (USPSTF) criteria. Limitations: Limitations include a paucity of literature, poor methodologic quality, and very few studies performed utilizing IASP criteria. Conclusion: Cervical discography performed according to the IASP criteria may be a useful tool for evaluating chronic cervical pain, without disc herniation or radiculitis. Based on a modified AHRQ accuracy evaluation and USPSTF level of evidence criteria, this systematic review indicates the strength of evidence as Level II-2 for diagnostic accuracy of cervical discography. Key words: Neck pain, headache, cervical discogenic pain, cervical intervertebral disc, cervical provocation discography, false-positive rates, diagnostic accuracy, outcomes, cervical facet joint pain, controlled diagnostic blocks

Diagnostic Validity of Criteria for Sacroiliac Joint Pain: A Systematic Review

A systematic literature review was conducted to determine the diagnostic validity of the criteria for sacroiliac (SI) joint pain as proposed by the International Association for the Study of Pain (IASP). Databases were searched up to September 2007. Quality of the studies was assessed using a Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool. Sensitivity, specificity, and diagnostic odds ratios (DOR) were calculated together with 95% confidence intervals (CI). Statistical pooling was conducted for results of provocative tests. Eighteen studies were included. Five studies examined the pattern of SI joint pain, whereas another 5 examined stressing test specific for SI joint pain. None of the studies evaluated the diagnostic validity of the SI joint infiltration or the diagnostic validity of the IASP criteria set as a whole. In all studies, the SI joint selective infiltration was used as a gold standard; however, the technique, medications, and required pain relief after the infiltration varied considerably between the studies. Taking the double infiltration technique as reference test, the pooled data of the thigh thrust test (DOR, 18.461; CI, 5.82 to 58.53), compression test (DOR, 3.88; CI, 1.7 to 8.9), and 3 or more positive stressing tests (DOR, 17.16; CI, 7.6 to 39) showed discriminative power for diagnosing SI joint pain. This review of clinical studies focused on the diagnostic validity of the IASP criteria for diagnosing SI joint pain. A meta-analysis showed that the thigh thrust test, the compression test, and 3 or more positive stressing tests have discriminative power for diagnosing SI joint pain. Because a gold standard for SI joint pain diagnosis is lacking, the diagnostic validity of tests related to the IASP criteria for SI joint pain should be regarded with care.

Challenges in the Diagnostic Conceptualization of CRPS-1 (Formerly Conceptualized as RSD)

Abstract From the previous issue, this article continues a discussion of the potentially confusing aspects of the diagnostic formulation for complex regional pain syndrome type 1 (CRPS-1) proposed by the International Association for the Study of Pain (IASP), the relevance of these issues for a proposed future protocol, and recommendations for clinical practice. IASP is working to resolve the contradictions in its approach to CRPS-1 diagnosis, but it continues to include the following criterion: “[c]ontinuing pain, which is disproportionate to any inciting event.” This language only perpetuates existing issues with current definitions, specifically the overlap between the IASP criteria for CRPS-1 and somatoform disorders, overlap with the guidelines for malingering, and self-contradiction with respect to the suggestion of injury-relatedness. The authors propose to overcome the last of these by revising the criterion: “[c]omplaints of pain in the absence of any identifiable injury that could credibly account for the complaints.” Similarly, the overlap with somatoform disorders could be reworded: “The possibility of a somatoform disorder has been thoroughly assessed, with the results of that assessment failing to produce any consistencies with a somatoform scenario.” The overlap with malingering could be addressed in this manner: “The possibility of malingering has been thoroughly assessed, with the results of that assessment failing to produce any consistencies with a malingering scenario.” The article concludes with six recommendations, and a sidebar discusses rating impairment for CRPS-1 (with explicit instructions not to use the pain chapter for this purpose).

Diagnostic Conceptualization for CRPS-1: Challenges in the IASP's Diagnostic Conceptualization for CRPS-1 (Formerly Conceptualized as RSD)

Abstract Complex regional pain syndrome-type 1 (CRPS-1) is a problematic diagnosis of a characteristic burning pain that is present without stimulation or movement, occurs beyond the territory of a single peripheral nerve, and is disproportionate to the inciting event. This article highlights some challenging aspects of the diagnostic formulation for CRPS-1 by the International Association for the Study of Pain (IASP) and provides recommendations to address the issues. First, the terminology, CRPS-1, was created specifically to replace the previous term, “reflex sympathetic dystrophy.” Unfortunately, no gold standard diagnostic tests exist for CRPS-1, and the concept itself has a long and continuing history of controversy, not the least factor of which is the lack of reliable diagnostic schemes. Next, IASP's criteria for CRPS-1 do not standardize the diagnostic process and depart from epidemiologic guidelines, particularly regarding continuing pain, allodynia, or hyperalgesia disproportionate to any inciting event. Further, the IASP protocol overlaps diagnostic criteria for somatoform disorders, eg, those in the American Psychiatric Association's diagnostic manual, DSM-IV-TR. Finally, according to the IASP protocol, the majority of CRPS-1 patients present with symptoms that are indistinguishable from those in the DSM-IV-TR guidelines, and the majority of CRPS-1 cases are indistinguishable from the formal definition of malingering.

Complex Regional Pain Syndrome Type I: Use of the International Association for the Study of Pain Diagnostic Criteria Defined in 1994

The objective was to assess the reported use in recent publications of the diagnostic criteria for complex regional pain syndrome type I (CRPS I) proposed by the International Association for the Study of Pain (IASP) in 1994. A literature search of MEDLINE (January 1996 to July 2000) was performed with use of the medical subject heading "reflex sympathetic dystrophy" and the free texts words "complex," "regional," "pain," and "syndrome." Publications in English, German, and Dutch were analyzed. From the search, 65 original publications were selected. Another 27 publications (referenced publications) that were referenced in the 65 original publications for the description of diagnostic criteria for CRPS I also were included. A standard form was used to assess a total of 92 publications. A sensitivity analysis was performed by means of analyzing three scenarios in which the diagnostic criteria were used as proposed and two combinations of less stringent criteria. Use of the diagnostic criterion pain was reported in 35 (38%) of the analyzed publications. None of the original publications satisfied the proposed IASP diagnostic criteria. Four (15%) of the referenced publications satisfied the proposed IASP diagnostic criteria. Ten (15%) of the original publications referred correctly to the referenced publications. With the less strict criteria used in scenarios 2 and 3, 2 (3%) and 3 (5%), respectively, of the original publications fulfilled these criteria. If the diagnostic criteria for CRPS I are not used uniformly, the populations in clinical studies may not be uniform either. Whether different authors are describing the same syndrome and whether their findings can be compared is open to question. On the basis of the results of this study, it is concluded that the IASP criteria for CRPS I are poorly used in clinical studies.

Complex regional pain syndrome

Since the early musings in the mid-1800s of Claude Bernard and his French neurological colleagues on the association of pain with the sympathetic nervous system, complex regional pain syndrome (CRPS) has both fascinated and perplexed practitioners. Some of the clearest and most interesting descriptions of ‘causalgia’ come from the American Civil War by one of Bernard’s students, Silas Weir-Mitchell. The low-velocity, high-mass missiles used in this confrontation (the ‘Minnie ball’) seemed to be particularly effective in inducing neuropathic pain associated with intense autonomic dysregulation. Weir-Mitchell’s depictions are clear and elegant, and as good as any clinical description that can be found in this century. 64 Many great minds have struggled with the pathophysiology of what came to be called ‘reflex sympathetic dystrophy’ in the later part of the 1900s and what has, since the Orlando consensus-based workshop of 1999, come to be called complex regional pain syndrome (CRPS) (Table 1). 37 63 85 From Leriche 46 and his vicious circles we have progressed through Livingston 47 and Sunderland 88 with the turbulence theory, and finally to the solid physiological information generated by the various animal models of causalgia, especially the chronic constriction injury model of Bennett and Xie. 5 Recently, the effort to understand the syndrome has turned towards consensus symposia. The first of these concerned taxonomy, as above. 37 85 A second Dahlem-type conference was conducted in regard to the guidelines for therapy, 84 and recently the International Association for the Study of Pain (IASP) sponsored a symposium in Cardiff, Wales in 2000 to discuss issues of pathophysiology and to amend the diagnostic considerations. 83 The epidemiology of the syndrome is very unclear. Although the syndrome has traditionally been considered rare, its ‘discovery’ by personal injury lawyers in the United States has caused a radical increase in the reporting of the syndrome (at least in the USA). The current diagnostic criteria, as set forth by the Committee of Classification of Chronic Pain of the IASP, have contributed to the liberalization of the diagnosis (Table 1). 63 This effort was extremely important in providing standardized diagnostic criteria, and caused a vast improvement in clinical communication and research homogeneity. It provided the hope that results could be generalized across studies, and in fact widespread use of these standardized criteria has helped all these things considerably. These criteria, while being very sensitive, greatly lack specificity. 92 1 31 The intent of the Orlando conference in 1994 was that these criteria should evolve on the basis of experience and empirical testing, and that they should be subject to systematic validation research over time. 37 62 85 This has been accomplished to some extent, and through a process of internal and external validation the opportunity to improve the specificity of the bedside diagnostic criteria is available. 92 1 31 Although the original IASP criteria required only subjective and potentially only historical signs and symptoms, the suggestions for improving these criteria are that some objectification and observed evidence be included. It is recommended that the diagnostic criteria be modified to include at least one symptom in each of the four diagnostic categories derived by factor analysis: sensory

Complex regional pain syndrome: are the IASP diagnostic criteria valid and sufficiently comprehensive?

This is a multisite study examining the internal validity and comprehensiveness of the International Association for the Study of Pain (IASP) diagnostic criteria for Complex Regional Pain Syndrome (CRPS). A standardized sign/symptom checklist was used in patient evaluations to obtain data on CRPS-related signs and symptoms in a series of 123 patients meeting IASP criteria for CRPS. Principal components factor analysis (PCA) was used to detect statistical groupings of signs/symptoms (factors). CRPS signs and symptoms grouped together statistically in a manner somewhat different than in current IASP/CRPS criteria. As in current criteria, a separate pain/sensation criterion was supported. However, unlike in current criteria, PCA indicated that vasomotor symptoms form a factor distinct from a sudomotor/edema factor. Changes in range of motion, motor dysfunction, and trophic changes, which are not included in the IASP criteria, formed a distinct fourth factor. Scores on the pain/sensation factor correlated positively with pain duration ( P<0.001), but there was a negative correlation between the sudomotor/edema factor scores and pain duration ( P<0.05). The motor/trophic factor predicted positive responses to sympathetic block ( P<0.05). These results suggest that the internal validity of the IASP/CRPS criteria could be improved by separating vasomotor signs/symptoms (e.g. temperature and skin color asymmetry) from those reflecting sudomotor dysfunction (e.g. sweating changes) and edema. Results also indicate motor and trophic changes may be an important and distinct component of CRPS which is not currently incorporated in the IASP criteria. An experimental revision of CRPS diagnostic criteria for research purposes is proposed. Implications for diagnostic sensitivity and specificity are discussed.