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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 13  |  Issue : 2  |  Page : 103-106

Evaluation of electrocardiogram as a biological signal for sex verification among fresh undergraduates in a Nigerian tertiary institution


1 Department of Physiological Sciences, Obafemi Awolowo University, Ile Ife, Nigeria
2 Health Centre, Cardiovascular Physiology Laboratory, Obafemi Awolowo University, Ile Ife, Nigeria

Date of Web Publication4-Aug-2016

Correspondence Address:
Muritala A Asafa
Department of Physiological Sciences, Obafemi Awolowo University, Ile Ife
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0189-7969.187707

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  Abstract 

Background: Sex verification using electrocardiogram (ECG) is a new application of the biological signal.
Objective: This study aimed to determine the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of an electrocardiographic score in sex verification.
Methods: A total of 2442 apparently healthy fresh undergraduates who presented for health screening in a tertiary institution were recruited for the study. The technical team documented the sex of the participants and had their resting 12-lead ECG recorded according to standard protocol. Two physicians who were blinded to the participants and the recorded sex utilized Ogunlade Sex Determination Electrocardiographic Score (OSDES) to determine the sex. The validity of OSDES was estimated using sex recorded by the technical team as the standard while the accuracy of scoring system was determined using receiver operating characteristic curve.
Results: The mean (± standard deviation) of age of the participants was 20.71 ± 3.62 years. Among the male population, true positives (TPs), false positives (FPs), false negatives (FNs), and true negatives (TN) were 1131, 49, 90, and 1172, respectively. Among the females TP, FP, FN, and TN were 1172, 90, 49, and 1131, respectively. Among males, the sensitivity, specificity, PPV, and NPV were 92.63% (95% confidence interval [CI]: 91.02-94.03%), 95.99% (95% CI: 94.73-97.02%), 95.85% (95% CI: 94.55-96.91%), and 92.87% (CI: 91.31-94.23%) respectively while among the females, the sensitivity, specificity, PPV, and NPV were 95.99% (95% CI: 94.73-97.02%), 92.63% (95% CI: 91.02-94.03%), 92.87% (95% CI: 91.31-94.23%), and 95.85% (95% CI: 91.02-94.03%) respectively. The area under curve was 0.943.
Conclusion: This study concluded that ECG has a reasonable level of sensitivity and specificity with excellent accuracy in verification of sex among fresh Nigerian undergraduates.

Keywords: Biological signal, electrocardiogram, sex verification, undergraduates


How to cite this article:
Asafa MA, Ogunlade O, Osasogie OE, Ayoka AO. Evaluation of electrocardiogram as a biological signal for sex verification among fresh undergraduates in a Nigerian tertiary institution. Nig J Cardiol 2016;13:103-6

How to cite this URL:
Asafa MA, Ogunlade O, Osasogie OE, Ayoka AO. Evaluation of electrocardiogram as a biological signal for sex verification among fresh undergraduates in a Nigerian tertiary institution. Nig J Cardiol [serial online] 2016 [cited 2022 Sep 26];13:103-6. Available from: https://www.nigjcardiol.org/text.asp?2016/13/2/103/187707


  Introduction Top


Electrocardiogram (ECG) has a lot of potentials which are yet to be explored. Sex differences had been reported to exist in various aspect of ECG; heart rate, QT intervals, QRS complex, and repolarization pattern. [1],[2],[3],[4] Sex of an individual can be identified prenatally or postnatally. Prenatal sex identification can be done noninvasively through ultrasonography. After birth, sex can be identified by physical outlook and/or physical examination. The concept of sex verification is very useful and sensitive issue especially in sports where men can deliberately pose as women to gain an advantage. The gold standard test for verification of sex is chromosomal analysis, an expensive procedure, and not readily available in the most developing countries. For ages, ECG was not mentioned as an investigation for sex verification. However, Ogunlade and Asafa in 2015 published the basis and potentials of ECG in sex verification among young adults following the development of a Scoring System called Ogunlade Sex Determination Electrocardiographic Score (OSDES) in Ile-Ife, Nigeria. [5] The masculine and feminine pattern of ECG among young adult Nigerians had been described. [6] The aim of this study was to determine the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of the ECG scoring system for sex verification among a large population of fresh undergraduates in a Nigerian tertiary institution.


  Methods Top


The study was carried out at Obafemi Awolowo University Health Centre, Ile-Ife, Southwestern Nigeria. Target population was fresh undergraduates who presented for medical screening. A total of 2442 students between the age of 15 and 41 years participated in the study. Inclusion criteria were apparently healthy young adult Nigerians while exclusion criteria were the presence of symptomatic systemic diseases, hypertension, and unwillingness to participate. Ethical clearance was obtained from the Ethics and Research Committee, Obafemi Awolowo University Teaching Hospitals, Ile-Ife, Nigeria. The participants were educated about the procedure and written informed consent obtained from them. Materials such as wristwatch, jewelry, coins, and mobile phones were removed to reduce electromagnetic interference and improve the quality of the ECG. The chest and the limbs were exposed, and ECG electrode placed according to internationally approved protocol. [7] The chest lead recordings (V1-V6) were obtained by the attachment of six electrodes to the anterior chest wall according to the conventional method; V1 at 4 th intercostal space right sternal edge, V2 at 4 th intercostal space left sternal edge, V3 at the point midway between V2 and V4, V4 at 5 th intercostal space left midclavicular line, V5 and V6 at the same horizontal line with V4 at left anterior axillary line and left midaxillary line, respectively. The six limb leads (I, II, III, aVF, aVL, and aVR) were recorded by the aids of four electrodes attached to the distal end of the limbs (one electrode per limb) according to the standard protocol for limb electrode placement. Identification number, age, and blood pressure were entered into the ECG machine while the technician documented the sex. The standard 12-lead resting ECG of each participant was obtained in the supine position during quiet respiration. The standard paper speed was 25 mm/s. The results were printed out. The ECGs were blinded for sex and name by the technicians. Two physicians who were blinded to the sex and name of the participants utilized OSDES to determine the sex of the individuals. Parameters (score range) assessed in ECG were; T-wave configuration in V1 (1-3), ST segment in V2 or V3 (1-3), QRS rotation (1-3), and heart rate (1-3). The total minimum and maximum scores were 4 and 12, respectively. [5] The total score was obtained by the summation of the point scored from ECG parameter. A total score of <7 was used to identify female while the total score of ≥7 was used to identify male [Table 1].
Table 1: Ogunlade Sex Determination Electrocardiographic Score


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The data were analyzed using IBM SPSS Statistics (International Business Machines Corporation, Armonk, New York, US). Descriptive analysis was performed on the patients' biodata. The sex determined by ECG (OSDES) was compared with the sex recorded by the ECG technician. Sensitivity, specificity, PPV, and NPV of OSDES were determined using sex recorded by technician as obtained through the physical appearance (PA) as gold standard.

Sensitivity = TP/TP + FN

Specificity = TN/FP + FN

PPV = TP/TP + FP

NPV = TN/FN + TN

Where TP = True positive, FN = False negative, TN = True negative, and FP = False positive.

TP - sex determined by PA and OSDES were positive, TN - sex determined by OSDES and PA were negative, FP - sex by PA was negative but sex by OSDES was positive, FN - sex by PA was positive, but sex by OSDES was negative. When the cases of males were considered, a male identified by OSDES as male or female was considered positive or negative, respectively. When cases of females were considered, a female identified by OSDES as female or male was considered positive or negative, respectively. [6] The accuracy of the scoring system was also tested using receiver operating characteristics (ROC) curve by determining the area under curve (AUC).


  Results Top


A total of 2442 young adults participated in this study. The mean ± standard deviation for age in years, weight in kilogram (kg), height in meter (m), and body mass index in kg/m 2 were 20.7 ± 3.6, 59.8 ± 12.7, and 1.66 ± 3.14, respectively. [Figure 1] shows a male ECG using OSDES; upright T-wave in V1 (3), elevation of ST segment in V2 or V3 (3), normal transition (2), and heart rate is >70 beats/min (1). The total OSDES = 9. [Figure 2] shows a female ECG; T-wave inversion in V1 (1), isoelectric of ST segment in V2 or V3 (1), normal transition (2) and heart rate >70 beats/min (1). The total OSDES = 5. From this study, OSDES was able to identify 1130 correctly out of 1221 males and 1171 out of 1221 [Table 2]. The agreement between the sex determined by OSDES and sex recorded by ECG technician was very good (k = 0.885, P < 0.001). Among the male population, TPs, FPs, FNs, and TNs were 1131, 49, 90, and 1172 respectively. Among the females TP, FP, FN, and TN were 1172, 90, 49, and 1131, respectively. Among males, the sensitivity, specificity, PPV, and NPV were 92.63% (95% confidence interval [CI]: 91.02-94.03%), 95.99% (95% CI: 94.73-97.02%), 95.85% (95% CI: 94.55-96.91%), and 92.87% (95% CI: 91.31-94.23%) respectively while among the females, the sensitivity, specificity, PPV and NPV were 95.99% (95% CI: 94.73-97.02%), 92.63% (95% CI: 91.02-94.03%), 92.87% (95% CI: 91.31-94.23%), and 95.85% (95% CI: 91.02-94.03%) respectively as shown in [Table 3]. The accuracy of OSDES for sex verification was tested using ROC [Figure 3]. The AUC was 0.943.
Figure 1: Electrocardiogram of a 22-year-old Nigerian male with; upright T-wave in V1 (3), elevation of ST segment in V2 or V3 (3), normal transition (2) and heart rate is >70 beats/min (1). The total Ogunlade Sex Determination Electrocardiographic Score = 9

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Figure 2: Electrocardiogram of a 24-year-old Nigerian female with; T-wave inversion (1), isoelectric ST segment (1), normal transition (2) and heart of 72 beats/min. Total Ogunlade Sex Determination Electrocardiographic Score = 5

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Figure 3: Sensitivity, Specificity and Accuracy of Ogunlade Sex Determination Electrocardiographic Score for sex verification in young adults. The area under curve was 0.943

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Table 2: Comparison between Ogunlade Sex Determination Electrocardiographic Score identified sex and sex recorded by electrocardiogram technician


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Table 3: Validity tests for OSDES


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  Discussion Top


Interpretation of ECG had been based on heart rate, rhythm, intervals, changes in segments, P-wave, QRS complex and T-wave duration, morphology, axis, and amplitudes which are used in clinical diagnosis of heart diseases/conditions. [2],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21] Little emphasis was placed on the classification of ECG into male and female patterns. The development of OSDES in 2015 at Obafemi Awolowo University, Ile-Ife, Nigeria paved the way for utilization of biological signal such as ECG as part of noninvasive test for assessment of sex in young individuals. [5] [Table 1] shows the scoring system (OSDES) used to classify the already blinded ECG into male or female categories.

[Table 3] shows the test of validity of OSDES with sensitivity and specificity of 95.99%, 92.63% and 92.63%, 95.99% for males and females. This showed that the scoring system (OSDES) is more sensitive in female than male, which is in contrast with what was earlier reported in a study done among older age group. [6] This may be because the earlier study was carried out among older age group. The AUC was 0.943, which showed an excellent level of accuracy of OSDES in sex verification among the study population. Sex verification using ECG is a new application which may have a lot of potentials both in sports and clinical settings. In sports, OSDES may be included as one of the initial screening tests for sex verification among young adults to exclude cases of deliberate cheating (men masquerading as women), drug use and abuse, intersex disorders or cardiovascular disorders such as congenital heart diseases, heart blocks, and cardiomyopathies. Among the general population of young adults, when a male presents asymptomatically with feminine ECG pattern or a female presents with masculine ECG pattern, the following conditions among others should be excluded; intersex disorders, drug use and abuse especially doping, cardiomyopathies, idioventricular rhythm, bundle branch block, preexcitation pattern and syndromes, congenital heart diseases, and persistent juvenile pattern of T wave changes. The potential of OSDES as anti doping test is in the fact that the scoring system may pick a sports woman who utilized drugs to achieve a masculinized body build to gain an advantage over the peers.


  Conclusion Top


This study showed that ECG has a reasonable level of sensitivity and specificity in verification of sex among fresh Nigerian undergraduates. ECG should be considered as a quick valid test in sex verification exercises. In sports, ECG could be useful as cheap, noninvasive anti-doping test in addition to biochemical test.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]


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