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Augmentation index (AIx) 
For AIx, the SphygmoCor tonometer is placed over the right radial artery and data 
are collected as previously described 
(27, 28)
.  The pressure waves are calibrated 
using systolic and diastolic BP obtained in the same arm.  The device then 
analyses the pulse wave using a validated generalized transfer function 
(29)
.  Wave 
forms collected over an 8-second period are averaged to produce peripheral and 
corresponding central (ascending aortic) pressure waveforms.  Ascending aortic 
pressure and AIx are derived from the central pressure waveform.  Aix is the 
difference between the main outgoing wave and the reflected wave (RW) of the 
central arterial waveform, expressed as a percentage of the central pulse pressure.  
It provides a measure of systemic arterial stiffness.  Since AIx is affected by heart 
rate (HR), values are adjusted to a standard HR of 75 beats/minute (AIx75).  An 
average of 3 measures is used.  The inter-observer difference for AI was found to 
be 0.23 ± 0.66% and the intra-observer difference was 0.49 ± 0.93% as compared 
to an average AI in healthy children of greater than 3%. 
5.1.9.
 
Markers of Neuropathy 
While there is substantial evidence of the epidemiology of neuropathy in adult diabetes 
patients, there is limited information available on the prevalence and determinants of 
neuropathy among youth with diabetes.  Given the large sample size, racial and ethnic 


Section 5B - Data Collection (Phase 3 - 1/2011, rev. 8/2011) 
Section 5B - Page 7 
 Cohort 
Study
 
diversity and sizeable numbers of youth with Type 2 diabetes, the SEARCH for Diabetes 
in Youth Study presents a unique opportunity to understand the natural history of diabetic 
neuropathy (both peripheral and autonomic).  Data to be collected during this visit 
include: 1) the Michigan Neuropathy Screening Instrument (MNSI), which includes a 
brief questionnaire, physical exam inspection, vibration sense, reflex test and 
monofilament test for peripheral neuropathy; and 2) cardiac autonomic neuropathy 
assessment using electrocardiogram analyses. 
5.1.9.1.
 
Peripheral neuropathy methods 
The Michigan Neuropathy Screening Instrument (MNSI) is designed to screen for the 
presence of peripheral diabetic neuropathy.  The MNSI is designed to be used in an 
outpatient setting and will be administered by trained technicians.  The first part of 
the screening instrument consists of 15 self-administered "yes or no" questions on 
foot sensation including pain, numbness and temperature sensitivity.  A higher score 
(out of a maximum of 13 points) indicates more neuropathic symptoms.  The 
questions were chosen from among those in the Neuropathy Screening Profile that 
showed the highest degree of specificity and sensitivity for diabetic neuropathy 
among normal subjects and those with a variety of neuromuscular disorders 
(30)
 and 
have been recently validated 
(31)
.  The second part of the MNSI is a brief physical 
examination involving 1) inspection of the feet for deformities, dry skin, hair or nail 
abnormalities, callous or infection, 2) semi-quantitative assessment of vibration 
sensation at the dorsum of the great toe using a 128 Hz tuning fork, 3) grading of 
ankle reflexes and 4) monofilament testing with a 10 g Semmes-Weinstein 
monofilament using a standard protocol.  Subjects with an MNSI score > 2, together 
with reduced/absent vibration sense, ankle reflexes, and monofilament testing will be 
considered to have diabetic neuropathy on screening. Other combinations of results 
will also be evaluated.
 
5.1.9.2.
 
CAN methods 
Measurement of HRV will be performed by trained and certified technicians.  The 
protocol is based on the software housed in the Sphygmacor instrument (ATCOR 
Medical: 
http://www.atcormedical.com/
).  A resting ECG will be completed for 5-10 
minutes.  Resting HRV time parameters that are captured include: HRV range
maximum, minimum; standard deviation, percent of consecutive beat-to-beat 
intervals that are greater than 50 milliseconds long (pNN50), Triangular index, and 
the root mean squared successive mean standard deviation (RMSSD), a measure of 
vagal index.  Resting frequency parameters captured include: low frequency max 
(Hz); High freq max (Hz); LF:HF ratio, LF power normalized; HF power normalized
Total power (ms
2
).   


Section 5B - Data Collection (Phase 3 - 1/2011, rev. 8/2011) 
Section 5B - Page 8 
 Cohort 
Study
 
5.1.10.
 

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