Interpretation of Autonomic Function Test

The autonomic function test consists of the tests that evaluate the sudomotor, cardiovascular adrenergic, and parasympathetic functions. As its importance grows, more and more medical institutions want to evaluate it properly. However, there are many variables to consider and difficulties in interpreting ambiguous results, which may lead to incorrect screening. This paper is intended to help provide an appropriate interpretation of autonomic function tests in clinical settings.

Comparison of autonomic function tests and high-sensitivity C-reactivity protein in overweight patients of polycystic ovarian syndrome and overweight controls

Objectives: Both polycystic ovarian syndrome (PCOS) and high body mass index (BMI) are associated with autonomic dysfunction. Most of the patients of PCOS have high BMI. Hence, BMI is likely to be a factor contributing to the autonomic dysfunction in PCOS. High-sensitivity C-reactive protein (hs-CRP) is a marker of inflammation and a predictor of future cardiovascular risk. PCOS patients have low-grade chronic inflammatory state. Coexistence of PCOS and obesity causes more increase in CRP, thereby further increasing the risk of cardiovascular morbidity. We have performed autonomic function tests and estimated hs-CRP in overweight patients of PCOS and compared our findings with the control group consisting of overweight normal subjects. Our aim is to find out whether the cardioautonomic and inflammatory changes seen in PCOS are due to the presence of increased weight or do the presence of increased weight add to the severity of these changes seen in PCOS. Materials and Methods: Cases consisted of 44 overweight patients of PCOS and controls included 44 healthy overweight subjects, all in the age group of 18–45 years. Autonomic function test consisted of three sympathetic and three parasympathetic reactivity tests. The following tests were done for parasympathetic reactivity: (a) Deep breathing test – expiration:inspiration ratio (E:I) was calculated. (b) Valsalva maneuver-Valsalva ratio was calculated. (c) Heart rate changes from lying to standing (LST) - 30:15 ratio was calculated. For assessing sympathetic reactivity, the following tests were used: (a) Isometric handgrip test – the difference between resting diastolic blood pressure (DBP) reading and the reading before release of hand grip is noted. (b) Cold pressor test (CPT) – The rise in DBP over the baseline DBP was noted. (c) Systolic BP (SBP) change in LST – the maximum fall in SBP was recorded. Measurement of serum hs-CRP was done using enzyme-linked immunosorbent assay. Results: We found that in the overweight PCOS group, there was a significant decrease in both sympathetic and parasympathetic reactivity than the overweight control group (p=0.000 for Valsalva ratio, 0.027 for 30:15 ratio, and 0.0005 for CPT). The difference between hs-CRP in controls and PCOS was also significant (P = 0.039). Conclusion: In our study, we concluded that the pathological changes due to PCOS could be attributed directly to the extent of inflammation measured by hs-CRP levels. These changes were not directly related to BMI as proven by comparing with controls (overweight non-PCOS subjects).