Laboratory Studies

The physical examination is unlikely to document the severity or the intensity of pain, and this is equally true of the laboratory study assessment of the patient. Abnormalities on screening and diagnostic tests do not necessarily prove the presence or absence of pain, nor do they correlate with the patient's stated magnitude of the pain or any claimed disability. For example, data reveal that tests for low back pain can be overinterpreted in up to 40% of patients and that pathology is discovered on the side opposite to the site of the primary complaint in 25% of patients.^[37] Laboratory studies are expensive and subject to error of interpretation, leading many times to the official reading concluding "clinical correlation is needed." The Agency for Health Care Policy and Research (AHCPR) reference guidelines for acute low back pain advocate little or no diagnostic testing for most patients in the first 4 to 6 weeks of symptoms.^[37] A "red flag" section warns that the findings of marked motor weakness or acute loss of bladder and/or bowel control merit expedited patient assessment. Few such guidelines for other common pain conditions exist. The practitioner who is contemplating invasive pain therapy will want to assess the patient for blood-borne infection, altered coagulation parameters, and evidence of metabolic disarray, metastatic

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It is crucial to appreciate how important laboratory tests may be to the patient with neuropathic pain. His or her eternal hope is that a test will finally pinpoint the exact and specific cause of the endless and mystifying pain. What the patient seeks is an explanation for what is wrong. Thus, an unrevealing test result does not answer this need for the patient but only details what is not present. This basic misunderstanding, and the implication (when presenting the fact that the laboratory facts are "negative") that the pain is not significant or real, results in considerable angst in the doctor-patient relationship.