Questionable necessity of nitroglycerin for diagnostic coronary artery examination using 320-row multi-detector computed tomography

Abstract

OBJECTIVE:

This study aims to analyze and compare the diagnostic effectiveness of 320-row multi-detector computed tomography for coronary artery angiography (MDCTA) in subjects with and without sublingual vasodilator (nitroglycerin).

MATERIALS AND METHODS:

From September 2015 to September 2016, 70 individuals without history of major cardiovascular diseases who underwent MDCTA for health examination were retrospectively categorized into sublingual nitroglycerin (NTG) and non-NTG groups. Medical history, CT dose index (CTDI), and multi-slice CT images were compared between two groups. A diameter of coronary artery (DA, mm) was computed and analyzed.

RESULTS:

A total of 41 males and 29 females (mean age: 55.43±8.84 years, range: 34– 76) were reviewed. Normal and abnormal MDCTA findings were noted in 54 and 16 participants, respectively, with the detection rate of coronary artery disease being 23%. There was no significant difference in inter-observer variability of coronary CTA image quality and diagnosis between the NTG and non-NTG groups among three experienced radiologists. Although the percentage dilatation of left anterior descending branch (LAD), right coronary artery (RCA) and left circumflex branch (LCX) following in the NTG group were 12.4%, 12.8% and 25.3%, respectively (p < 0.01), there was no significant difference in image quality and diagnosis between the two groups.

CONCLUSIONS:

Despite the recommendation of routine nitroglycerin use for subjects undergoing computed tomography for coronary artery angiography, our results showed no significant advantage of its use in improving image quality and rate of diagnosis accuracy.

Keywords

Multi-detector computed tomography for coronary artery angiography (MDCTA)coronary artery disease nitroglycerin

1 Introduction

The cardiovascular disorder was the leading etiology of mortality and morbidity in the Western world. According to the American Heart Association, approximately 15.4 million people >20 years of age in the United States in the year 2010 had ischemic heart disease (IHD). In 2009, the overall coronary heart disease (CHD) death rate was 116.1 per 100,000 people [1 –4]. Early diagnosis of coronary artery disease was effective for timely treatment.

Coronary computed tomography angiography (CTA) has been a reliable and noninvasive technique to detect coronary artery disease. The current generation of multi-detectors computed tomography (MDCT) systems provides the cross-sectional and longitudinal imaging of the coronary arteries with a high spatial and temporal resolution. Wide volume CTA allows for a remarkable decrease in scan time and time of breath-hold, resulting in decreased radiation dose and contrast medium. Its advantages include a high sensitivity in detecting coronary artery stenosis >50% and an excellent negative predictive value [5 –8]. Before coronary CTA examination, sublingual nitroglycerin is usually used to dilate the coronary vessels. Sublingual nitroglycerin capsule or spray is routinely used to treat angina attacks and to maximally dilate the epicardial coronary arteries during coronary angiography [9 –11]. Although arterial dilatation is a merit for the evaluation of coronary artery, the concomitant increase in heart rates is disadvantageous for coronary computed tomography angiography (CTA) [12]. Besides, the typical side effects of nitroglycerin, including headache, dizziness, lightheadedness, nausea, and flushing, may occur. Indeed, a small fraction of the patients with stable angina experienced incapacitating headaches and refused to take sublingual nitroglycerin [13].

The objective of this study was to evaluate the impact of nitroglycerin on the diagnostic effectiveness of 320-row multi-detector computed tomography (MDCT) for coronary artery examination to refine the guidelines for coronary computed tomography angiography (CTA) in a regular health examination setting.

2 Materials and methods

2.1 Study population

From September 2015 to September 2016, the medical records of 70 individuals undergoing 320-row multi-detector computed tomography for coronary artery angiography (MDCTA) for health examination at a tertiary referral center were retrospectively reviewed. The subjects were divided into two groups, including those receiving sublingual nitroglycerin (NTG) before the examination (i.e., NTG group) and those without (i.e., non-NTG group). Subjects with a history of major cardiovascular diseases, including coronary artery disease, cerebrovascular disease, peripheral artery occlusion disease, those taking beta-blockers (e.g., metoprolol, propranolol) during the study period and/or did not complete the examination were excluded. The protocol and procedures of the current study were reviewed and approved by the Institutional Review Board (IRB) of the Institute. Table 1 was shown the information of study population. A total of 70 subjects, including 41 males and 29 females (mean age: 55.43±8.84 years, range: 34– 76), mean body weight: 70.93±13.60 kg, body mass index (BMI): 25.45±3.56 kg/m2 in were reviewed. The baseline characteristics of the two groups (NTG group, n = 35; Non-NTG group, n = 35) were summarized in Table 1. Meanwhile, the size of samples between male and female were 41 (NTG = 19 vs Non-NTG = 22) and 29 (NTG = 16 vs Non-NTG = 13). The abnormal and normal groups were defined as value of Agatston higher than 100 and no greater than 100.

Table 1
Demographic, anthropometric, and hemodynamic characteristics of recruited subjects (N = 70)

Variables Mean 95% CI

Lower Up SD Min Max

Age (yr) 55.43 53.16 57.69 8.84 34 76

Height (cm) 166.34 164.12 168.57 8.68 152 183

Weight (kg) 70.93 67.45 74.41 13.60 46 113

BMI (kg/m²) 25.45 24.54 26.36 3.56 18 37

Heart rate before exam (beats/min) 70.49 67.64 73.34 11.14 49 103

Systolic blood pressure (mmHg) 131.41 126.54 136.28 19.00 89 179

Heart rate during exam (beats/min) 62.62 59.27 65.97 13.08 42 105

Variables	Mean	95% CI
Age (yr)	55.43	53.16	57.69	8.84	34	76
Height (cm)	166.34	164.12	168.57	8.68	152	183
Weight (kg)	70.93	67.45	74.41	13.60	46	113
BMI (kg/m²)	25.45	24.54	26.36	3.56	18	37
Heart rate before exam (beats/min)	70.49	67.64	73.34	11.14	49	103
Systolic blood pressure (mmHg)	131.41	126.54	136.28	19.00	89	179
Heart rate during exam (beats/min)	62.62	59.27	65.97	13.08	42	105

CI: confidence interval; BMI: body-mass index.

2.2 Study parameters and interpretation

The demographic (i.e., age, gender), anthropometric (i.e., body height (cm), body weight (kg), BMI (kg/m²)) and hemodynamic (i.e., heartbeats (bits/min), systolic blood pressure (mmHg), heart rate (bits/min)) characteristics of all subjects were recorded. Medical history (yes or no) was also reviewed for coronary artery disease-related risk factors, including serum cholesterol concentration (>200 mg/dL or not), smoking (yes or no), diabetes (yes or no), contrast medium allergy (yes or no), arrhythmia (yes or no), asthma (yes or no), operation (yes or no) and hypertension (yes or no). Radiologically, CT data from multi-slice CT images, diameter of the coronary artery (DA, mm) was acquired for comparison between the two groups. Three experienced radiologists (with at least ten-year experience in MDCT image interpretation) who were blinded to the grouping of the subjects were responsible for image quality and diagnosis. Evaluation of the image quality based on the 16 segment AHA model and each vessel was rated by consensus agreement using a modified Likert scale. Fair of image quality (Likert score of 1 or 2) was defined as impaired image quality limited by excessive noise or poor vessel wall, limitations in lower contrast resolution. Acceptable of image quality (Likert score of 3, 4 or 5) was defined as impact of image noise, limitations of low contrast resolution and delineation of vessel walls are minimal.

2.3 Scanning equipment and protocol

We used the 320-row MDCT scanner (Aquilion One, Toshiba, Medical Systems, Otawara, Japan). It was the fastest CT in the world with a rotation speed of 0.275 seconds. At first, a non-enhanced calcium scoring scan was performed. The scan volume was determined from the tracheal bifurcation to the base of the heart. The whole heart was images in a single heart beat using a maximum of 16 cm craniocaudal coverage. Five minutes after the administration of sublingual nitroglycerin (i.e., NTG group) by the radiology nurse, coronary CTA examination started to perform. A tri-phasic injection of intravenous contrast media was used and the total 60– 80 mL (depending on individual’s body weight) of non-ionic contrast media of 100% Iohexal (Omnipaque 350) was administered. First, 50– 70 mL of contrast media was injected at 6 mL/s and followed by 20 mL of 50% contrast/saline. Then, a saline chaser of 25 mL was administered at 3 mL/s. We used automated peak enhancement detection in the left ventricle using a threshold of +180 Hounsfield unites in order to synchronize the arrival of contrast media and the scan. All images were acquired during a breath-hold about 5 s. The parameters of coronary CTA were as follows: slice/collimation: 0.5/280– 320 (140– 160 mm), the field of view limited to the heart (200– 220 mm), slice thickness 0.5 mm, increment 0.25 mm, rotation time 275 ms, tube voltage 120 kV, and tube current 100– 750 mA.

2.4 Statistical data analysis

The Statistical Product and Service Solution (SPSS) software (SPSS, Inc., Chicago, IL, USA V22) was used for all statistical analysis. The methods included box-plots, descriptive statistics, Mann-Whitney U test for similarity. The quantitative variables were expressed as means±standard deviation (SD), and categorical variables are expressed as frequencies or percentages by Chi-Square testing. Differences with a p-value <0.05 were considered statistically significant. There were no any missing data in this study. The cronbach’s alpha was used to evaluate inter-observer variability.

3 Results

3.1 Comparison of demographic and hemodynamic parameters between subjects taking nitroglycerin and those without

All participants completed the examination without any complication. There was no statistically significant difference between the two groups in age, body weight, BMI, heartbeats, and blood pressure (Table 2). Mildly increased systolic blood pressure and heart rate were noted in the NTG group compared to those in the non-NTG group without reaching statistical significance.

Table 2
Differences in demographic, anthropometric, and hemodynamic characteristics between subjects receiving nitroglycerin (NTG group) and those without (non-NTG group)

Variable Mean±SD

Non-NTG (N = 35) NTG (N = 35) p-value*

Age (yr) 53.29±8.05 56.54±8.88 0.150

Height (cm) 167.07±8.55 165.39±8.92 0.378

Weight (kg) 71.06±12.68 72.14±14.14 0.694

BMI (kg/m²) 25.3±3.24 26.14±3.48 0.332

Heart rate (bits/min) 72.54±11.94 67.23±9.61 0.121

Systolic blood pressure (mmHg) 127.31±16.87 136.26±20.56 0.113

Heart rate in the exam (bits/min) 61.31±14.38 64.35±11.36 0.192

Variable	Mean±SD
Age (yr)	53.29±8.05	56.54±8.88	0.150
Height (cm)	167.07±8.55	165.39±8.92	0.378
Weight (kg)	71.06±12.68	72.14±14.14	0.694
BMI (kg/m²)	25.3±3.24	26.14±3.48	0.332
Heart rate (bits/min)	72.54±11.94	67.23±9.61	0.121
Systolic blood pressure (mmHg)	127.31±16.87	136.26±20.56	0.113
Heart rate in the exam (bits/min)	61.31±14.38	64.35±11.36	0.192

^*Significance of difference determined by Mann-Whitney U test.

3.2 Coronary artery disease-related factors and image quality in subjects taking nitroglycerin and those without

Comparison of the presence of the diagnosis of coronary artery disease, arrhythmia, hypertension, diabetes, heart disease, contrast medium allergy, asthma, smoking, and operation as well as serum cholesterol level, gender, and image quality between the two groups demonstrated no significant difference (Table 3). The rating scales of image quality were 0 for fair and 1 for acceptable. The evaluation of inter-observer variability by values of cronbach’s alpha for three experienced radiologists were no less than 0.75 (Table 4).

Table 3
The difference of coronary artery disease (CAD)-related factors and image quality between subjects receiving nitroglycerin (NTG group) and those without (non-NTG group)

Factor Level Group

Non-NTG NTG p-value*

(N = 35) (N = 35)

Diagnosis of CAD Negative 25 29 0.39

Positive 10 6

Sex male 22 19 0.63

female 13 16

Arrhythmia no 32 34 0.61

yes 3 1

Hypertension no 23 20 0.62

yes 12 15

Diabetes no 32 33 0.99

yes 3 2

Heart Disease no 31 33 0.67

yes 4 2

Cholesterol no 23 28 0.28

yes 12 7

Contrast Medium Allergy no 30 28 0.75

yes 5 7

Asthma no 31 35 0.99

yes 1 0

Smoking no 29 26 0.59

yes 6 9

Operation no 16 18 0.81

yes 19 17

Image Quality fair 1 3 0.61

acceptable 34 32

Factor	Level	Group
Diagnosis of CAD	Negative	25	29	0.39
	Positive	10	6
Sex	male	22	19	0.63
	female	13	16
Arrhythmia	no	32	34	0.61
	yes	3	1
Hypertension	no	23	20	0.62
	yes	12	15
Diabetes	no	32	33	0.99
	yes	3	2
Heart Disease	no	31	33	0.67
	yes	4	2
Cholesterol	no	23	28	0.28
	yes	12	7
Contrast Medium Allergy	no	30	28	0.75
	yes	5	7
Asthma	no	31	35	0.99
	yes	1	0
Smoking	no	29	26	0.59
	yes	6	9
Operation	no	16	18	0.81
	yes	19	17
Image Quality	fair	1	3	0.61
	acceptable	34	32

^*Significance of difference determined by Chi-Square test. CAD: coronary artery disease.

Table 4

The evaluation of inter-observer variability by Cronbach’s alpha for three experienced radiologists (with at least ten-year experience in MDCT image interpretation) rating scale with quality

Artery	Group	Sample Size	Cronbach’s Alpha	Overall
				Cronbach’s Alpha
LAD	Non-NTG	35	0.898	0.899
	NTG	35	0.990
RCA	Non-NTG	35	0.990	0.899
	NTG	35	0.990
LCX	Non-NTG	35	0.750	0.750
	NTG	35	0.990

3.3 Coronary CTA findings

Coronary CTA examination showed normal and abnormal findings in 54 and 16 subjects, respectively. There are multiple methods of assessing coronary artery lumen stenosis. An estimate of luminal diameter stenosis is commonly used. Most cardiac CTA workstations can provide quantification of coronary arterial stenosis. Definition of normal CTA finding including absence of plaque and no luminal stenosis is negative for obstructive coronary artery disease. Abnormal CTA findings included plaques with <49%, 50– 69% or 70– 99 % stenosis of coronary arterial lumen. The detection rate of coronary artery disease was about 23%. No interference was noted in subjects with arrhythmia during the CTA examination. The inter-observer variability in image quality determination and diagnosis making among the three radiologists was not significant between images from the two groups. The comparison of coronary artery diameters in the two groups was shown in Table 5. Normal subjects were negative for obstructive coronary artery disease. CTA findings show no evidence of atheroma plaque or luminal stenosis. Typical CTA images from normal subjects without premedication (Fig. 1) and those receiving nitroglycerin (Fig. 2), as well as those from subjects with stenotic coronary arteries without (Fig. 3) and with (Fig. 4) nitroglycerin, are shown. Significant increases in diameters of the three major coronary arterial branches with percentage dilatation of 12.4%, 12.8%, and 25.3% for left anterior descending branch (LAD), right coronary artery (RCA) and left circumflex branch (LCX), respectively, were noted in the NTG group (all p < 0.01, Fig. 5). According to our result, we confirmed the clinical impact about sublingular nitroglycerine for significant coronary artery dilatation. But this phenomenon cannot significantly affect radiologists in detecting coronary artery heart disease.

Table 5
Comparison of coronary artery diameters (mm) between subjects receiving nitroglycerin (NTG group) and those without (non-NTG group)

Artery Group Mean Median SD Min Max p-value* Percentage

dilatation^#

LAD Non-NTG 3.49 3.50 0.44 2.50 4.40 0.001 12.4%

NTG 3.92 3.90 0.53 2.90 5.20

RCA Non-NTG 3.63 3.70 0.82 2.10 5.80 0.009 12.8%

NTG 4.09 4.10 0.61 2.90 5.10

LCX Non-NTG 2.89 2.90 0.57 1.70 4.10 <0.001 25.3%

NTG 3.63 3.50 0.79 2.10 5.50

Artery	Group	Mean	Median	SD	Min	Max	p-value*	Percentage
LAD	Non-NTG	3.49	3.50	0.44	2.50	4.40	0.001	12.4%
	NTG	3.92	3.90	0.53	2.90	5.20
RCA	Non-NTG	3.63	3.70	0.82	2.10	5.80	0.009	12.8%
	NTG	4.09	4.10	0.61	2.90	5.10
LCX	Non-NTG	2.89	2.90	0.57	1.70	4.10	<0.001	25.3%
	NTG	3.63	3.50	0.79	2.10	5.50

^*Significance of difference determined by Mann-Whitney U test. #Percentage dilatation = [(Mean Diameter of Artery in NTG – Mean Diameter of Artery in Non-NTG)/(Mean Diameter of Artery in Non-NTG)×100% ]; SD: standard deviation; LAD: left anterior descending branch. LCX: the left circumflex branch. RCA: right coronary artery.

Fig.1

A 42-year-old female was undergoing 320-row MDCT coronary angiography examination without taking nitroglycerin, showing no significant stenosis of coronary arteries including (A) LAD, (B) LCX, and (C) RCA. LAD: the left anterior descending branch. LCX: the left circumflex branch. RCA: right coronary artery.

Fig.2

A 60-year-old male was undergoing 320-row MDCT coronary angiography examination after taking nitroglycerin, demonstrating no significant stenosis of coronary arteries including (A) LAD, (B) LCX, and (C) RCA.LAD: the left anterior descending branch. LCX: the left circumflex branch. RCA: right coronary artery.

Fig.3

A 62-year-old male was undergoing 320-row MDCT coronary angiography examination without taking nitroglycerin, revealing >50% stenosis of (A) LAD (white arrows), without stenosis in (B) LCX and (C) RCA. LAD: the left anterior descending branch. LCX: the left circumflex branch. RCA: right coronary artery.

Fig.4

A 59-year-old female receiving 320-row MDCT coronary angiography examination after taking nitroglycerin, showing >75% stenosis (white arrows) of (A) LAD and (C) RCA as well as >50% stenosis (white arrows) in (B) LCX. LAD: the left anterior descending branch. LCX: the left circumflex branch. RCA: right coronary artery.

Fig.5

Differences in diameters of coronary arteries between subjects receiving nitroglycerin (NTG group) and those without (non-NTG group). LAD: the left anterior descending branch. LCX: the left circumflex branch. RCA: right coronary artery.

3.4 Diagnostic performance between using NTG or not

In the Table 6, the normal rates between Non-NTG and NTG groups were 48.15% and 51.85%. At the same time, the abnormal rates between Non-NTG and NTG groups were 56.25% and 43.75%. The experimental results were demonstrated that almost tiny difference between Non-NTG and NTG groups in this study.

Table 6
The diagnostic performance of using NTG or not between in the normal and abnormal group

Group NTG Total

Non-NTG NTG

Normal 26 (48.15)% 28 (51.85%) 54

Abnormal 9 (56.25%) 7 (43.75%) 16

Group	NTG	Total
Normal	26 (48.15)%	28 (51.85%)	54
Abnormal	9 (56.25%)	7 (43.75%)	16

4 Discussion

Advanced development in MDCT scanner hardware, software, and image processing algorithms had resulted in a dramatic improvement in scanning coverage, spatial, temporal, and contrast resolution for better image quality. At the same time, patient safety had been improved via strategies of reducing radiation and contrast medium dosage. The high negative predictive value of coronary CTA makes it a suitable modality for excluding significant coronary artery disease. One of the advantages of 320-row MDCT is its excellent diagnostic accuracy for the evaluation of obstructive coronary artery disease. On a patient level, a negative predictive value of 100% and a diagnostic accuracy of 95% had been shown for the detection of >50% stenosis [1, 8]. Although current practice encourages the routine use of beta-blockers and nitroglycerin before coronary CTA examination in an attempt to enhance image quality through heart rate reduction and coronary artery dilatation [14], these medications are not always free of side-effects [15, 16]. The current study was the first to investigate the necessity of premedication for subjects undergoing coronary 320-row CTA through investigating the impact of uncontrolled heart rate and non-dilated coronary artery on image interpretation in a health examination setting. Our results demonstrated no significant difference in image quality and interpretation between subjects with nitroglycerin and those without.

During the coronary CTA examination, sublingual nitroglycerin is commonly administrated to dilate coronary vessels for enhancing image quality to facilitate interpretation [10 , 17– 18]. In clinical practice, nitroglycerin is used for the rapid dilation of the coronary artery and is widely administered to relieve angina attacks [19, 20]. Headaches and dizziness were the most common side-effects associated with the use of nitroglycerin [13]. Although, the true incidence of headache with sublingual nitroglycerin is not known. In a dose-ranging research, the incidence of nitroglycerin-induced headache was dose-dependent, increasing from 0 with placebo to 3(6%), 5(10%), 6(12%), and 8(16%) after giving 0.2, 0.4, 0.8, and 1.6 mg doses of nitroglycerin spray, respectively [21]. Dizziness was typically the result of nitroglycerin-induced hypotension [22]. More severe side effects include a decrease in cardiac output/blood pressure [23, 24]. Postural hypotension and reflex tachycardia may occur due to overdosing on sublingual nitroglycerin [9, 13]. Besides, reflex tachycardia could result in more motion artifacts on coronary CTA [14, 25].

The current concept for patient safety is to decrease the dosage of radiation and contrast medium. In this study, we focused on the impact of using sublingual nitroglycerin in subjects undergoing health screening examination on image quality and interpretation. Moreover, a beta-blocking agent (e.g., metoprolol), which is widely used as a premedication for heart rate suppression before coronary CTA [26, 27], was not used. Our findings showed that nitroglycerin caused 12.4%, 12.8%, and 25.3%, dilatation in the left anterior descending branch (LAD), right coronary artery (RCA) and left circumflex branch (LCX), respectively (Table 5). Previous studies have reported that the location of nitroglycerin-induced coronary artery dilatation was influenced by coronary dominance (i.e., the respective contribution of the right and left coronary vessels). The predominant dilatation of the LCX after nitroglycerin administration in the current study (p < 0.001) was consistent with that of previous studies [25, 28]. Nevertheless, despite the significant dilatation in subjects taking nitroglycerin, especially in peripheral segments, there was no significant difference in the image quality and diagnostic performance when compared with those without premedication (Table 6). Our findings, therefore, suggested that premedication may not be necessary during the 320-row MDCT coronary angiographic examination, especially in the setting of health screening.

There were a few limitations in this study. First, the limited sample size of the current study precluded a strong conclusion being drawn from our findings. Second, we did not investigate the potential influence of coronary artery calcium scoring on diagnostic accuracy. Third, conduction of our study on symptom-free subjects without known cardiovascular diseases imposed a selection bias so that the results might not be extrapolated to the real-world clinical setting. Fourth, despite satisfactory image quality and data interpretation in our subjects without using beta-blocker, we did not include a group with beta-blocker for comparison. Finally, the nature of a single-center study limited the applicability of our findings to institutes with different diagnostic radiology equipment.

5 Conclusion

The results of the current study demonstrated a lack of significant impact of nitroglycerin on image quality and diagnostic performance for subjects undergoing coronary CT angiography for health examination, suggesting that medication-induced coronary arterial dilatation may not be necessary for 320-row MDCT coronary artery examination in the setting of health screening.

Conflict of interest

We declare that we have no conflict of interest.

Footnotes

Acknowledgments

The authors thank E-Da Hospital in Taiwan for partial financial support in this study with contract No: EDAHP105015, EDAHP106017, EDAHP107010 and EDAHP109034. Meanwhile, the authors also thank Ministry of Science and Technology in Taiwan for partial financial support with contract No:106-2118-M-214-001.

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Variable	Mean±SD
	Non-NTG (N = 35)	NTG (N = 35)	p-value*
Age (yr)	53.29±8.05	56.54±8.88	0.150
Height (cm)	167.07±8.55	165.39±8.92	0.378
Weight (kg)	71.06±12.68	72.14±14.14	0.694
BMI (kg/m²)	25.3±3.24	26.14±3.48	0.332
Heart rate (bits/min)	72.54±11.94	67.23±9.61	0.121
Systolic blood pressure (mmHg)	127.31±16.87	136.26±20.56	0.113
Heart rate in the exam (bits/min)	61.31±14.38	64.35±11.36	0.192

Questionable necessity of nitroglycerin for diagnostic coronary artery examination using 320-row multi-detector computed tomography

Abstract

OBJECTIVE:

MATERIALS AND METHODS:

RESULTS:

CONCLUSIONS:

Keywords

1 Introduction

2 Materials and methods

2.1 Study population

2.3 Scanning equipment and protocol

2.4 Statistical data analysis

3 Results

3.1 Comparison of demographic and hemodynamic parameters between subjects taking nitroglycerin and those without

Table 6 The diagnostic performance of using NTG or not between in the normal and abnormal group Group NTG Total Non-NTG NTG Normal 26 (48.15)% 28 (51.85%) 54 Abnormal 9 (56.25%) 7 (43.75%) 16

5 Conclusion

Conflict of interest

Footnotes

Acknowledgments

References

Table 6
The diagnostic performance of using NTG or not between in the normal and abnormal group

Group NTG Total

Non-NTG NTG

Normal 26 (48.15)% 28 (51.85%) 54

Abnormal 9 (56.25%) 7 (43.75%) 16