Journal of Diabetology

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 10  |  Issue : 1  |  Page : 21--24

Peripheral neuropathy and its clinical correlates in Type 2 diabetic subjects without neuropathic symptoms in Nnewi, South-Eastern Nigeria


Ogonna Celestine Oguejiofor1, Chikezie Hart Onwukwe1, Chidiebele Malachy Ezeude1, Ejike Kenneth Okonkwo1, Justin Chibueze Nwalozie1, Charles Uzoma Odenigbo2, Charlotte Blanch Oguejiofor3,  
1 Department of Medicine, Endocrinology, Diabetes and Metabolism Unit, Nnamdi Azikiwe University Teaching Hospital, Nnewi, Anambra, Nigeria
2 Department of Medicine, Nephrology Unit, Nnamdi Azikiwe University Teaching Hospital, Nnewi, Anambra, Nigeria
3 Department of Obstetrics and Gynaecology, Nnamdi Azikiwe University Teaching Hospital, Nnewi, Anambra, Nigeria

Correspondence Address:
Dr. Chikezie Hart Onwukwe
Department of Internal Medicine, Nnamdi Azikiwe University Teaching Hospital, Nnewi, Anambra
Nigeria

Abstract

Background: Peripheral neuropathy (PN) is a risk factor for foot disease in type 2 diabetes mellitus (T2DM). There are scanty data on prevalence of PN and its clinical correlates in Nigerian T2DM subjects without neuropathic symptoms. Objectives: To evaluate the prevalence and clinical correlates of PN diagnosed using objective methods in T2DM subjects without symptoms of PN. Materials and Methods: This is a cross-sectional study involving T2DM subjects at the Diabetes Clinic of Nnamdi Azikiwe University Teaching Hospital (NAUTH), Nnewi, Nigeria. History was obtained and physical examination done on subjects. Fasting plasma glucose (FPG) done on the day of assessment and values of glycated haemoglobin (HbA1c), and fasting lipid profile done within the preceding three months- were obtained from subjects' clinic folders. Diabetic Neuropathy Symptom Score (DNSS) was used to identify subjects without neuropathic symptoms. PN was diagnosed using tuning fork, and two biothesiometers. Data collection was done using researcher-administered study proforma. Data were analyzed using SPSS version 20. Results: 524 subjects [244 (46.6%) males and 280 (53.4%) females] were recruited for the study. 223 (42.6%) of these subjects did not have neuropathic symptoms and PN tested further with 3 objective methods. PN prevalence with tuning fork, analog and digital biothesiometers were 71.5%, 14.8% and 14.8% respectively. All clinical variables evaluated were poor predictors of PN (P > 0.05). Conclusion: PN diagnosed by objective methods is present in South-Eastern Nigerian T2DM subjects who do not have symptoms of PN. Tuning fork diagnosed PN much more than the other methods reflecting its subjectivity.



How to cite this article:
Oguejiofor OC, Onwukwe CH, Ezeude CM, Okonkwo EK, Nwalozie JC, Odenigbo CU, Oguejiofor CB. Peripheral neuropathy and its clinical correlates in Type 2 diabetic subjects without neuropathic symptoms in Nnewi, South-Eastern Nigeria.J Diabetol 2019;10:21-24


How to cite this URL:
Oguejiofor OC, Onwukwe CH, Ezeude CM, Okonkwo EK, Nwalozie JC, Odenigbo CU, Oguejiofor CB. Peripheral neuropathy and its clinical correlates in Type 2 diabetic subjects without neuropathic symptoms in Nnewi, South-Eastern Nigeria. J Diabetol [serial online] 2019 [cited 2020 Aug 7 ];10:21-24
Available from: http://www.journalofdiabetology.org/text.asp?2019/10/1/21/245898


Full Text



 Introduction



Diabetes mellitus (DM) is a metabolic disorder characterised by chronic hyperglycaemia. Peripheral neuropathy (PN) is a major complication of DM which contributes immensely to the development of foot disease.[1] This is associated with increasing lower extremity amputation rates and mortality in DM patients.[2] Diabetic PN (DPN) may be undetected and dormant in DM patients resulting in serious complications. The most common form of DPN is a chronic, symmetrical, length-dependant and sensorimotor polyneuropathy known as distal symmetric polyneuropathy. This generally presents as painful neuropathy, but up to 50% of patients with neuropathy might be asymptomatic – easily resulting in delayed diagnosis, reduced quality of life and increased mortality.[3],[4]

PN is common even in type 2 DM (T2DM) patients presenting without symptoms of PN. Mao et al.[5] in 2014 reported a 69% prevalence of PN among asymptomatic T2DM patients using Sudoscan. Oguejiofor et al.[6] in 2010 also reported that PN diagnosed using various methods is prevalent in asymptomatic T2DM patients in Nnewi, South-Eastern Nigeria. Ogbera et al.[7] in Lagos, South-West Nigeria reported that PN was prevalent among T2DM patients and that age >60 years and poor glycaemic control were significant predictors of PN in these patients. Because of the paucity of data on prevalence and clinical correlates of PN among asymptomatic T2DM patients in Nigeria, we carried out this research work using objective methods in determining PN among Nigerian T2DM patients without clinical symptoms of PN.

Study objectives

The aim of this study is to evaluate the prevalence and clinical correlates of PN in T2DM patients without symptoms of PN.

 Materials and Methods



This is a cross-sectional study involving T2DM patients attending the diabetes clinic of Nnamdi Azikiwe University Teaching Hospital (NAUTH), Nnewi, South-Eastern Nigeria. The inclusion criterion was adult T2DM patients presenting consecutively in the NAUTH diabetes clinic. Exclusion criteria included the presence of foot disease, type 1 DM and acute illness. The study participants were recruited consecutively over 5 months period and written informed consent obtained from them. Biodata, duration of DM, medications used and the presence of symptoms suggestive of PN were obtained from the study participants. Weight (in kilogrammes) was measured using a weighing balance with their footwear off and their height (in metres) measured with a stadiometer. The Body Mass Index (BMI) in kilogrammes per square metre (kg/m2) was determined by dividing weight by the square of the height. Using a non-stretch tape, waist circumference (WC) was measured midway between the lower ribs and the highest point of the iliac crest while hip circumference (HC) was measured at the widest diameter of the hip (in centimetres). The waist-to-hip ratio (WHR) was taken as the ratio of WC to HC. Blood pressure measurement was done on the right arm using an Accosson mercury sphygmomanometer with the patient in a sitting position.

PN was diagnosed using three methods-128 Hz vibration tuning fork, and two biothesiometers (a digital type and an analogue type). The diabetic neuropathy symptom score (DNS) was used to identify patients with neuropathic symptoms as a DNS >1 confirmed the presence of neuropathic symptoms.[8] [Table 1] shows the DNS.{Table 1}

The biothesiometer objectively measures vibration sensation and determines the vibration perception threshold (VPT) and each of the two types was used in study participants. With the subject lying in a supine position on an examination couch, testing was commenced by applying the vibrator of each biothesiometer to the pulp of the big toe of each foot. The vibrator was held in such a way that the weight of the vibrator furnished a standard pressure on the vibrator button with the probe balanced vertically on the pulp of the great toe. The vibrator was held steady and the subject instructed to concentrate all attention on the test site and to verbally report the first appearance of the sensation of vibration by saying ‘yes’,. The amplitude of the vibrator button was set as low as possible at the start of testing and increased until the patient perceived vibration. The voltage on the biothesiometer display at that instant was recorded as threshold 1 (TH1). This threshold is usually higher than the actual threshold due to the reaction time of the patient. Two further threshold readings (TH2 and TH3) were obtained at the test site, and the mean of the last two readings used to determine the VPT for each foot.

Records of fasting plasma glucose (FPG) done on the day of assessment and records of the following investigations done within the preceding 3 months-glycated haemoglobin (HbA1c), and fasting lipid profile (total cholesterol, triglycerides, high-density lipoprotein cholesterol and low-density lipoprotein cholesterol), were obtained from the patients' clinic folders.

Global obesity was defined as BMI ≥30 kg/m2 while overweight was defined as BMI of >25 kg/m2 in the study participants.[9] Abdominal obesity was defined as WC >94 cm for males and >80 cm for females;[10] or WHR >0.90 for males and >0.85 for females.[9] Hypertension was defined as BP >140/90 mmHg or use of anti-hypertensive medications.[11] DM[12] was defined as FPG >7 mmol/L on at least two different days and poor glycaemic control defined as HbA1c >6.5%.[13] PN was defined as vibration loss to 128 Hz tuning fork; or VPT >25 Volts[14] with any of the digital or analogue biothesiometers.

Data collection was done using researcher-administered study pro forma. Data were analysed using SPSS version 20 (IBM Corporation, California, USA). Continuous variables were presented as mean + standard deviation while categorical variables were presented as proportions (in percent). Continuous variables were compared using Student t-test. Binary logistic regression model was used to determine predictors of PN. P < 0.05 defined statistical significance.

 Results



A total of 524 patients (244 [46.6%] males and 280 [53.4%] females) were recruited for the study. Out of a total 524 patients, 301 (57.4%) of these patients (102 males and 199 females) had PN symptoms, whereas 223 (42.6%) of these patients (100 males and 123 females) did not have neuropathic symptoms (n = 223/524). [Table 2] shows the clinical characteristics of patients without neuropathic symptoms. There was no significant sex difference in the clinical variables.{Table 2}

The PN prevalence with a tuning fork, analogue and digital biothesiometers were 71.5%, 14.8% and 14.8%, respectively, in T2DM patients without neuropathic symptoms. [Table 3] shows the association between clinical variables and PN in T2DM patients without neuropathic symptoms. Age, DM duration, blood pressure, anthropometry, glycaemic and lipid indices were not significant predictors of PN diagnosed with biothesiometry (P > 0.05).{Table 3}

 Discussion



Diabetic patients who do not have neuropathic symptoms following assessment with symptom scores may have PN when assessed using more objective methods. Our study supports this assertion and showed that absence of neuropathic symptoms does not indicate the absence of objective PN. This agrees with previous reports.[5],[6],[7],[15]

Our study involved 223 (42.6%) diabetic patients without symptomatic PN out of a pool of 524 T2DM study population. Further evaluation of this population without symptoms of PN with more objective diagnostic tools showed that tuning fork detected PN in 71.5% and biothesiometry only in 14.8%. The high prevalence detected by tuning fork assessment also reflects its relative subjectivity compared to the more sensitive and specific biothesiometer.

Comparison of various methods for detecting DPN in Nigerian T2DM patients without neuropathic symptoms was reported by Oguejiofor et al. in 2010.[10] Their study patients without symptomatic DPN (30.8%) were determined following history taking (n = 37/120). The united kingdom screening test (Signs score), aesthesiometry and biothesiometry diagnosed DPN in 43.2% (n = 16/37), 40.5% (n = 15/37) and 29.7% (n = 11/37) of their asymptomatic patients, respectively. The 2010 study[10] agreed with ours in several ways. In both studies, biothesiometry detected the least prevalence of PN (29.7% vs. 14.8%), the higher detection reported by the 2010 study[10] probably resulting from their lower diagnostic threshold (VPT) of 20V for PN compared to our 2017 study with VPT of 25V. The higher prevalence rate by aesthesiometry (40.5%) done with the Weinstein enhanced sensory test (WEST) 10 g monofilament compared to biothesiometry is not unexpected. The 10 g monofilament has a limitation to detect PN at pressure points in the feet of the African compared to Caucasians because of the much more thickened (keratinised) soles of the feet, such that many false positive cases of PN are detected, increasing overall prevalence values detected by aethesiometry. biothesiometry, which is a gold standard for assessing PN has been found to have a higher sensitivity and specificity in diagnosing PN.[8] By this method, up to 14.8% of diabetic patients without ‘warning’ symptoms of PN, actually had PN, and are subject to risks for diabetic foot disease resulting from PN.

The study unlike the 2010 study[10] showed that several clinical variables such as age, duration of DM, blood pressure, anthropometry, glycaemic and lipid indices, were not significant predictors of PN diagnosed by biothesiometry in DM patients without symptoms of PN. That study[10] duration of DM a significant predictor for PN diagnosed using biothesiometry in DM patients without symptoms of PN. The difference in the diagnostic VPT for PN between the two studies (20 V vs. 25 V) may have accounted for this disparity.

Study strength and limitations

The major strength of this study was the use of biothesiometry, which is the gold standard test for PN assessment, in the study participants. Limitations of the study include the absence of diagnostic accuracy testing of symptom score and tuning fork compared to biothesiometry, and the cross-sectional design of the study.

Recommendation

Detection of PN in diabetic patients without ‘warning’ symptoms of PN indicates that this population of DM patients are exposed to all the risks for DM Foot Syndromes emanating from PN. Efforts should be made to screen all DM patients (with or without symptoms of PN) presenting to specialist health facilities with sensitive instruments like the biothesiometer to detect PN early and intervene appropriately to decrease morbidity and mortality arising from PN-related diabetes foot syndromes.

 Conclusion



PN diagnosed using tuning fork and biothesiometry is prevalent in Southeastern Nigerian T2DM patients without symptoms of DPN. Tuning fork detected PN much more than biothesiometry, reflecting its apparent subjectivity in diagnosing PN in Nigerian diabetic patients without symptoms of PN compared to biothesiometry. Biothesiometry with VPT of ≥25 volts is more sensitive and more specific in diagnosing PN.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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