Complex regional pain syndrome underdiagnosed

The Journal of Family Practice. 2005 June;54(6):524-532

June 1, 2005|Family Medicine

Anna Quisel, MD;James M Gill, MD, MPH;Peter Witherell, MD

CRPS type 1 is an under-recognized problem in limbs recovering from fracture or immobilized post-stroke.

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No single test identifies all persons with CRPS type 1; there is no objective gold standard for diagnosis

The absence of an objective gold standard does not mean CRPS type 1 is not a “real” disorder.¹² In developing diagnostic criteria for CRPS, the IASP turned to models developed for other conditions without objectively measurable findings: the International Headache Society (IHS) classification and the Diagnostic and Statistical Manual of Mental Disorders (DSM). These descriptive systems are based largely on history and self-reported symptoms rather than on clinical signs and laboratory tests. The accuracy of these types of diagnostic criteria is refined over time, through repeated, controlled validation studies using the best means available.¹¹

Specificity of criteria. Specificity has been tested using controls with neuro-pathic conditions.^11,12 In these studies, nonblinded clinicians applied CRPS type 1 diagnostic criteria, except the exclusion criterion, to patients who had either CRPS type 1 or neuropathic pain from other causes. Many persons with peripheral neuropathy met criteria for CRPS type 1. However, as stated in the IASP criteria, the diagnosis of CRPS type 1 is not considered until common causes of neuropathic pain and post-traumatic limb pain have been excluded.⁴ As long as the primary care provider considers and rules out other causes of pain, the clinically relevant specificity of these criteria is likely much higher.

Sensitivity of criteria varies.The sensitivity in these studies is based on a non-independent reference standard. Patients with CRPS type 1 were chosen for these studies using clinical criteria, and these criteria were reapplied by study clinicians to determine sensitivity.^11,12 This method does not allow any determination of whether cases of CRPS type 1 might be missed by the criteria. Sensitivity measured in this way more closely resembles interobserver reliability—the likelihood that different clinicians using the same diagnostic criteria will reach the same diagnosis— and it appears quite good, especially for IASP criteria, in these 2 studies.^11,12

However, when interobserver reliability has been directly studied, albeit in small studies of 3 and 6 observers, only Veldman’s criteria achieve good reliability; IASP and Bruehl’s criteria appear unreliable ( TABLE 3).^15,16 However, IASP and Bruehl’s criteria do fall within the range of reliability of other clinical assessments including medical fitness for a job and shoulder disorders.¹⁵

TABLE 1
Diagnostic criteria for CRPS type 1*

NAME	CRITERIA
IASP 1994 consensus criteria⁴	Criteria 2, 3 and 4 are necessary for a diagnosis of CRPS type 1.¹⁰ Type 1 is a syndrome that develops after an initiating noxious event. Spontaneous occurrence of pain in the absence of an external stimulus, allodynia (pain due to a mechanical or thermal stimulus that normally does not provoke pain), or hyperalgesia (exaggerated response to a stimulus that is normally painful) that is not limited to the territory of a single peripheral nerve, and is disproportionate to the inciting event. There is or has been evidence of edema, skin blood flow abnormality, or abnormal sudomotor (sweating) activity in the region of the pain since the inciting event. This diagnosis is excluded by the existence of conditions that would otherwise account for the degree of pain and dysfunction.
Bruehl’s criteria: IASP-family¹¹	Continuing pain disproportionate to any inciting event. Patient must report at least 1 symptom in each of the 4 following categories: a) sensory: reports of hyperesthesia b) vasomotor: reports of temperature asymmetry or skin color changes or skin color asymmetry c) sudomotor/edema: reports of edema or sweating changes or sweating asymmetry d) motor/trophic: reports of decreased range of motion or motor ysfunction (weakness, tremor, dystonia) or trophic changes (hair, nail, skin) Must display at least 1 sign in 2 or more of the following categories: e) sensory: evidence of hyperalgesia (to pinprick) or allodynia (to light touch) f) vasomotor: evidence of temperature asymmetry or skin color changes or asymmetry g) sudomotor/edema: evidence of edema or sweating changes or sweating asymmetry h) motor/trophic: evidence of decreased range of motion or motor dysfunction (weakness, tremor, dystomia) or trophic changes (hair, nail, skin)
Veldman’s criteria¹³	Presence of 4 out of 5 symptoms: a) Diffuse pain during exercise b) Temperature differences between affected and unaffected extremity c) Color differences between affected and unaffected extremity d) Volume differences between affected and unaffected extremity e) Limitations in active range of movement of the affected extremity Occurrence or increase of symptoms during or after use Symptoms in an area larger than the area of the primary injury
*IASP definition of CRSP 1: A variety of painful conditions following injury which appears regionally having a distal predominance of abnormal findings, exceeding in both magnitude and duration the expected clinical course of the inciting event and often resulting in significant impairment of motor function, and showing variable progression over time. (All 3 criteria sets use this definition.)

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