Assessing autonomic dysfunction in early diabetic neuropathy: the Survey of Autonomic Symptoms

Abstract

Objective: Autonomic symptoms may occur frequently in diabetic and other neuropathies. There is a need to develop a simple instrument to measure autonomic symptoms in subjects with neuropathy and to test the validity of the instrument.

Methods: The Survey of Autonomic Symptoms (SAS) consists of 11 items in women and 12 in men. Each item is rated by an impact score ranging from 1 (least severe) to 5 (most severe). The SAS was tested in observational studies and compared to a previously validated autonomic scale, the Autonomic Symptom Profile (ASP), and to a series of autonomic tests.

Results: The SAS was tested in 30 healthy controls and 62 subjects with neuropathy and impaired glucose tolerance or newly diagnosed diabetes. An increased SAS score was associated with the previously validated ASP (rank order correlation=0.68; p<0.0001) and with quantitative measures of autonomic function: a reduced quantitative sudomotor axon reflex test sweat volume (0.31; p<0.05) and an abnormal 30:15 ratio (0.53; p<0.01). The SAS shows a high sensitivity and specificity (area under the receiver operating characteristic curve 0.828) that compares favorably with the ASP. The SAS scale domains had a good internal consistency and reliability (Cronbach α=0.76). The SAS symptom score was increased in neuropathy (95% confidence interval [CI] 2.99-4.14) compared to control (95% CI 0.58-1.69; p<0.0001) subjects.

Conclusions: The SAS is a new, valid, easily administered instrument to measure autonomic symptoms in early diabetic neuropathy and would be of value in assessing neuropathic autonomic symptoms in clinical trials and epidemiologic studies.

Figure 1. The Survey of Autonomic Symptoms (SAS) symptom score and total symptom impact score (TIS) by age

Groups were divided by age (<60 years and ≥60 years). (A) The SAS symptom score is greater in neuropathy subjects <60 years (p < 0.001) and ≥60 years (p = 0.027). (B) The SAS TIS is greater in neuropathy subjects <60 years (p < 0.001) and ≥60 years (p = 0.014). Although both the symptom score and the TIS showed a slight increase with age, this was not significant. The box plot represents the median, 10th, 25th, 75th, and 90th percentiles as vertical boxes with error bars. Ctl = control subjects; Neur = neuropathy subjects.

Figure 2. Receiver operating characteristic curves for the Survey of Autonomic Symptoms (SAS) symptom score, total symptom impact score (TIS), and Autonomic Symptom Profile (ASP)

(A) SAS, (B) TIS, (C) ASP. The SAS symptom score (area under the curve = 0.828) shows a slightly greater sensitivity and specificity compared to the ASP (area under the curve = 0.812) but this was not significant (p = 0.682).