To establish normative values in children and adolescents for Quantitative Sudomotor Axon Reflex Test (QSART), Heart Rate Deep Breathing (HRDB), and Valsalva Ratio (VR).

We previously reported normative values of orthostatic HR and HR change for children and adolescents, but normative data for other components of autonomic reflex testing in that age group are lacking. That has led to improper utilization of adult norms.

Healthy children and adolescents between 8-19 years were recruited between 2003-2010 at Mayo Clinic-Rochester. Subjects were instructed to follow routine testing preparation and hold potentially interfering medications. QSART volumes at standardized sites (using Q-Sweat), HRDB, and VR were derived. The effect of age and sex on these parameters was assessed, and percentiles of normal were calculated.

QSART was performed on 101 subjects (48 female); volumes were not significantly different by sex, but there was a significant positive correlation with age. Percentiles were therefore calculated for a younger (8-13 years) and older (14-19 years) age-group. The 5^th percentile of normal for younger/older groups was 0.02/0.08 µL (forearm), 0.13/0.37 (proximal leg), 0.13/0.40 (distal leg), and 0.00/0.00 (foot). At the foot, even the 10^th percentile was 0.00/0.02, suggesting absent sweat responses at the foot should be considered a normal finding.

HRBD and VR were calculated for 108 subjects (52 female). Values did not differ by sex; HRDB showed a significant negative correlation with age, VR showed a trend (p=0.05) towards lower values with age.  The 5^th percentile of normal for the younger/older age groups were 15.4/13.3 bpm (HRDB) and 1.66/1.62 (VR).

QSART volumes among children and adolescents increase with age, while HRDB and VR already start to decrease with age before adulthood. These observations underline the importance of creating dedicated normative values for the young, and the need for different normative values even within that age-group.