HbA1c and glucose control are only in part predicting diabetic polyneuropathy (DPN).
In addition, the term „diabetic neuropathy” stands for very different disease entities,
affecting the different types of nerve fibers, comprising the sensory-motor- or autonomic
nervous system. Therefore we used skin auto-fluorescence, which partially reflects
advanced glycation end products (AGE) accumulated in the skin, and quantitative sensory
testing (QST), as well as heart rate variability as a surrogate parameter for autonomic
neuropathy, to study whether all symptoms of DPN correlate in a similar manner with
skin auto-fluorescence in 81 type 2 diabetic patients in a cross-sectional study.
All statistical analyses were performed using non-parametric tests, correlations were
calculated by Spearman and Kendall tau correlation coefficients.
As expected, diabetes duration correlated positively with skin auto-fluorescence,
whereas no correlation between HbA1c and skin auto-fluorescence could be found. Concerning
thermal sensory testing of the feet, there was a negative correlation between cold
detection threshold (CDT) and skin auto-fluorescence, whereas the correlation with
warm detection threshold was positive. Fittingly, thermal sensory limen (TSL) correlated
positively with skin auto-fluorescence. In contrast, no correlations between mechanical
sensory tests or heart rate variability and skin auto-fluorescence could be detected.
Therefore, DPN comprises a variety of symptoms, which are not necessarily comparable.
In addition, while symptoms are more prevalent in the lower extremities, comparable
results concerning thermal sensory testing could be detected on the patients' hands,
showing similar DPN affection of the upper extremities.
