The present cross-sectional study was conducted
in an outpatient setting at the Vydehi Institute of Medical Sciences and
Research Centre, Bangalore, India between February 2016 and November 2017.
Informed consent was obtained from the participants, and the study design was
approved by the Vydehi Institutional Ethics Committee. Consecutive participants
aged > 18 or < 65 years with prediabetes were recruited for the study (n = 414). Prediabetes was defined according to the criteria of the American Diabetes Association with a fasting plasma glucose (FPG) of 100–125 mg/dL or a 2-hour oral glucose tolerance test (OGTT) PG of 140–200 mg/dL or hemoglobin A1c (HbA1c) of 5.7%–6.4%. Both known and newly diagnosed cases of prediabetes were recruited for the study. Previously diagnosed cases of prediabetes that did not fulfil the diagnostic criteria for prediabetes at the time of recruitment were excluded from the study. Participants with chronic alcohol consumption, an active foot ulcer, and secondary causes of DPN such as rheumatological conditions, alcoholic polyneuropathy, untreated hypothyroidism, and hereditary neuropathy were excluded. A detailed clinical history was taken, and demographic information (age, sex, and ethnicity), life-style factors (smoking), and family history of diabetes were collected using standardized self-report questionnaires. Cigarette smoking status was assessed per the National Health Interview Survey criteria and included both former and current smokers.16 Participants were questioned for the presence of unsteady gait, paresthesia, burning sensation, aching pain or tenderness in the legs or feet, and numbness and weakness of the lower extremities. A detailed clinical and neurological examination was performed in all the participants. Anthropometric measurements including weight, height, and body mass index (BMI; kg/m2) were recorded in all the participants. Height and weight were taken in duplicate according to standardized procedures, and the averages of these measurements were used in the analyses. Blood pressure was recorded in the right arm to the nearest 2 mm Hg with a clock model aneroid blood pressure apparatus (Diamond, Pune, India) after a 5-min rest with the patient in a sitting position. 1. Neurological examinations A detailed neurological examination was performed according to standardized procedures and included assessment of pin-prick, temperature, vibration sensation, and Achilles reflex, each of which were tested twice on each subject.17 The Diabetic Neuropathy Symptom Score (DNS), Modified Neuropathy Disability Score (NDS), and vibration perception threshold (VPT) using biothesiometry were used to screen for DPN. DNS: The DNS score is a 4-item, validated and easy-to-perform symptom score used for the screening of DPN.18, 19 The maximum score for DNS is 4 points, and a score of ? 1 suggests an abnormality. NDS: The modified NDS, as described by Young et al., is a validated examination score for the detection of DPN.20 Neuropathic deficits in the feet were determined using the NDS, derived from the examination of vibration (using a 128-Hz tuning fork), pin-prick sensation (using Neurotip), temperature sensation (using warm and cool rods), and Achilles tendon reflex (using a tendon hammer). The 3 perceptions were scored 0 if present and normal, and 1 if absent, reduced, or uncertain. On either side, the ankle reflex was scored 0 if present and normal, 1 if present with reinforcement and 2 if absent. The maximum score was 10. The minimum acceptable criteria for a diagnosis of peripheral neuropathy using NDS are moderate signs with or without symptoms (NDS ? 6) or moderate symptoms with at least mild signs of neuropathy (NDS ? 3).20 VPT: The VPT was assessed using a biothesiometer (Dhansai Lab, Mumbai, India) at 6 different body sites including the great toe, first metatarsal, third metatarsal, fifth metatarsal, medial arch, and heel in a graduated manner from 0 volts upwards. Patients were asked to give a verbal response once they could feel the vibration. Three cycles of readings were recorded at each site, and the mean was calculated. A mean value of > 15
volts was considered abnormal. 21
DPN was defined as any of the following: (i)
modified NDS ? 6, (ii) NDS ? 3 or < 6 with a DNS score of ? 1, and (iii) VPT > 15.
OGTT was carried out in
the morning (7:00 A.M. to 11:00 A.M.) after a 10-hour overnight fast.
Participants were asked to avoid heavy physical activity on the day before
examination and to refrain from smoking before and during the test. Fasting
venous blood glucose was sampled, and 75-g anhydrous glucose was then given,
and second sample was drawn two hours after ingestion. Fasting samples for
glycated hemoglobin, lipids, serum thyroid-stimulating hormone (TSH), and
vitamin B12 were also collected and analyzed using a fully automated Beckman
Coulter DXC 860i Auto Analyzer (Beckman Coulter, California, USA).
2.2. Statistical analyses
All statistical analyses were performed using
SPSS version 23.0. Data are presented as mean ± SD for continuous variables and
as percentages for categorical variables. Between-group comparisons were
performed using the student’s t-test for continuous data and the chi-squared
test for categorical data. Pearson’s or Spearman’s correlation coefficient was
computed to evaluate the relationship between the variables. Univariate and
multivariate logistic regression analyses were performed to determine the
relationships between the presence of DPN and various demographic/lifestyle
factors (namely, age, sex, BMI, and smoking habits) and biochemical parameters
(namely, FPG, HbA1c, hemoglobin, serum TSH, vitamin B12, and lipid components).
Unadjusted and adjusted odds ratios (ORs) and 95% confidence intervals were
estimated via logistic regression analyses. Statistical significance was set at
P < 0.05.