The level of small nerve fiber dysfunction does not predict pain in diabetic Neuropathy: a study using quantitative sensory testing.
OBJECTIVE
To determine whether small nerve fiber dysfunction predicts pain in diabetic neuropathy using quantitative sensory testing of thermal thresholds.


METHODS
Diabetic patients with or without painful neuropathy (n=191) were studied. Small nerve fiber function was assessed by quantitative sensory testing of cold detection and heat pain thresholds. Subjects were also categorized as being hyperalgesic (<10th percentile) or hyposensitive (>90th percentile) by comparing with normative data. Vibration perception threshold, a large nerve fiber function, was measured using a biothesiometer (Bio-medical Instrument, Newbury, OH).


RESULTS
In the patients with pain, cold stimulus was detected after a greater reduction in temperature from baseline (-3.7 degrees C vs. -0.6 in the no-pain group, P<0.0001). There were no differences between the pain and painless groups in the heat pain tests, with hyperalgesia noted in about 60% of subjects. Vibration perception threshold and loss of ankle reflexes were significant determinants of pain, but together they accounted for only 6.8% of the variance. If these were removed from the model, cold detection threshold became a significant determinant of pain but accounted for only 3.0% of the variance.


CONCLUSIONS
Quantitative sensory testing of small nerve fiber function is a useful test to detect the presence of neuropathy, and overall diabetic patients with neuropathic pain have more sensory loss. However, small nerve fiber abnormalities detected by quantitative sensory testing do not predict the presence of pain in diabetic neuropathy.
Sorensen
Lea
L
Diabetes Centre, Royal Prince Alfred Hospital Sydney, Australia Discipline of Medicine, University of Sydney, Australia. lea@email.cs.nsw.gov.au
Molyneaux
Lynda
L
Yue
Dennis K
DK
D000344:Afferent Pathways; D000368:Aged; D003929:Diabetic Neuropathies / Q000150:complications / Q000175:diagnosis*; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000175:diagnosis* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers; D009460:Neurologic Examination / Q000379:methods*; D010147:Pain Measurement / Q000379:methods*; D017288:Pain Threshold; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013697:Thermosensing