Sensory Abnormalities in Post-surgical Peripheral Neuropathy: A Comparison of Subjects With and Without Severe Pain Using Normative Data

Detailed Summary

The concept of normality is a cornerstone in medical practice and research. As an example, in clinical chemistry, a laboratory value based on a plasma sample exceeding the +/- 1.96 x standard deviation (SD) range, referenced from normative material, is, per definition, outside the normal range (the reference interval). Obviously, a number of reasons for this deviation may exist. The sample value could reflect a "true" pathological condition but could also be caused by error, e.g., technical measurement error, drug-interaction error, random error, or reflect a value occurring in 5% of the healthy population. Conversely, a sample value in the normal range evidently does not exclude a pathological condition. The reference interval is calculated from a large number of healthy subjects sampled across age, anthropometrics, ethnicity, and gender. Normative reference intervals are certainly of help, particularly in the screening of subjects, but may be of limited value in the detailed assessment of pathophysiological processes. Also, increasing the number of analyses in a subject expands the risk of making a type I error (acquiring "false" positive results). The likelihood of one or more type I errors in the analysis of 10 different laboratory values in one subject is impressive 46% (\[1 - 0.95\^10\] =0.46). It is well-known that multiple measurements are commonly performed in medical practice and research, but corrected significance levels are not always used.

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