Comparative Evaluation of Salivary and Serum High-Sensitive C-Reactive Protein in Acute Myocardial Infarction

Abstract

Aim:

The aim of this study is to comparatively evaluate the serum and salivary high-sensitive C-reactive protein (hs-CRP) in patients with acute myocardial infarction (MI).

Subjects and Methods:

The study group consisted of 60 patients of whom 30 were MI patients and 30 were controls. Serum hs-CRP was assessed using particle-enhanced immunoturbidimetric assay. Saliva hs-CRP is determined using a microplate reader cum UV photospectrometer from BMG.

Results:

In this study, levels of both serum and salivary hs-CRP in control and MI patients showed a positive correlation. Saliva can be used as an alternative biofluid to determine hs-CRP in MI patients.

Conclusion:

Saliva can be used as a alternative biofluid to determine the risk as well as to determine prognosis in acute myocardial infarction.

INTRODUCTION

Myocardial infarction (MI) is the very harmful manifestation of coronary heart disease with serious consequences in mortality and morbidity.[1] Coronary atherosclerosis plays an important underlying role in many patients with MI. The development and progression of atherosclerotic lesion is a chronic inflammatory process.[2]

This inflammatory progress regulates the production of the acute phase proteins such as C-reactive protein (CRP), fibrinogen, and serum amyloid A.[3] These risk factors are gaining importance in prediction of vascular events and also in determining the prognosis of MI.[4] American Heart Association (AHC)/Centers for Disease Control and Prevention guidelines identified CRP as the best of all existing inflammatory markers for using in clinical practice.[5]

Even though blood is the primary biofluid in almost all the diagnostic procedures, its collection causes discomfort, pain, and risk.[6] Evaluation of biomarkers in saliva is noninvasive and can be done multiple times in a day and its collection procedure requires minimal training.[7] Hence, evaluating CRP in saliva helps to testpatients with acute MI and to determine the prognosis of future coronary vascular events in such patients. The present study is designed to evaluate and compare the salivary and serum hs-CRP in patients with acute MI.

SUBJECTS AND METHODS

The study was performed after approval from the ethical committee and written informed consent was obtained from each patient involved in the study. The study group comprised 60 patients of which 30 were individuals with coronary artery disease and 30 were control group.

The study group was divided into:

• Group I – Individuals diagnosed with coronary artery disease (angina/MI)

• Group II – Patients without any coronary artery diseases.

Patients for Group I were selected from the intensive care unit, department of cardiology, having angina within 48 h and diagnosed with coronary artery disease. Patients for Group II were randomly selected with the same age range as that of Group I from the outpatient department of oral medicine and radiology and department of general medicine without any known cardiac diseases. Inclusion criteria consisted of patients with the complaint of angina within 48 h and diagnosed with coronary artery diseases. Individuals with autoimmune disorders, musculoskeletal disorders, and malignancies, individuals who had undergone recent surgery/trauma, and individuals who had infectious diseases such as fever, cold, and throat infections were excluded from our study.

Detailed medical history and oral examination was done before including in the study. For estimation of serum hs-CRP, 3 ml of venous blood was drawn under aseptic techniques. After rinsing the mouth thoroughly, the patient was asked to expel around 3 ml of saliva into a microcentrifuge tube.

The samples were centrifuged at 14,000 rpm for 10 min. The serum hs-CRP was done using particle-enhanced immunoturbidimetric assay. Roche/Hitachi Cobas C systems automatically calculate the analyte concentration of each sample. Saliva hs-CRP is determined using a microplate reader cum UV photospectrometer from BMG.

RESULTS

In this study, of 60 patients, there were 26 males (86.67%) and 4 females (13.33) in both MI group and in control group. Of 30 controls, the mean salivary hs-CRP was 238.38pg/ml, and the serum hs-CRP level was 1.38mg/L [Graph 1]. In the MI group, the mean salivary hs-CRP level was 1519.53 pg/ml and serum hs-CRP was 17.61mg/L [Graph 2]. Salivary and serum hs-CRP levels between the control and MI group were statistically analyzed by Pearson correlation and Student's t-test, and it was statistically highly significant (P < 0.001; Table 1]. The correlation between salivary and serum hs-CRP was done using a scatter diagram, and a positive correlation was observed in both control and MI groups. The correlation was statistically highly significant in control [Graph 3] and in MI groups [Graph 4].

Graph 1.

Graphical distribution of mean salivary high-sensitive C-reactive protein in both control and myocardial infarction groups

Graph 2.

Graphical distribution of mean serum high-sensitive C-reactive protein in both control and myocardial infarction groups

Table 1.

Student t-test and P values for salivary and serum high-sensitive c-reactive protein between control and myocardial infarction groups

	Group	n	Mean	SD	T	P
Age	Control	30	56.90	7.45	0.85	0.397
	MI	30	58.63	8.27
Salivary hs-CRP (pg/ml)	Control	23	238.48	94.78	9.21	<0.001**
	MI	30	1519.53	660.41
Serum hs-CRP (mg/L)	Control	30	1.38	0.47	17.67	<0.001**
	MI	30	17.61	5.01

**Significant at 1%. SD: Standard deviation, hs-CRP: High-sensitive c-reactive protein, MI: Myocardial infarction, n: Number, P: Probability value

Graph 3.

Scatter diagram showing the positive correlation between salivary high-sensitive C-reactive protein (hs-CRP) (pg/ml) and serum hs-CRP (mg/l) in the control group

Graph 4.

Scatter diagram showing the positive correlation between salivary high-sensitive C-reactive protein (hs-CRP) (pg/ml) and serum hs-CRP (mg/l) in the myocardial infarction group

DISCUSSION

MI is an acute coronary syndrome that occurs during the course of atherosclerosis. Initiation and progression of the disease remains silent for many years until the formation of atherosclerotic plaques. This plaque rupture can take place at any time and causes the occlusion of the coronary artery if it persists for ½ h leads to MI.[5]

CRP level is also increased in any type of acute infections, trauma, and recent hospitalizations.[5,8] Hence, in our study, the patients were carefully evaluated to eliminate acute infections, autoimmune disorders, trauma, and surgery. According to Auer et al., the plasma levels of CRP start to rise after 6 h of acute stimulus and reach the peak within 48 h.[9] Hence, our study group included patients who had MI within 48 h. In our study, diabetic (36.67%), hypertensive (30%), and smoking (33.33%) were greater in the MI group than in the control group.[6] However, in our study, the results were not statistically significant due to a small number of patients in the study group.

In the present study, serum hs-CRP levels were higher in patients with acute MI when compared to the patients without any cardiac diseases. There was a statistically significant difference between MI patients and controls in their serum CRP levels. This was in accordance with the studies done by Kushner I et al.,[10] Auer et al.,[9] de Beer et al.,[11] Tracy et al.,[12] and Ridker et al.[13] Tracy, in their study, showed that there was a greater difference between MI patients and controls in the CRP levels. According to Irving Khushner et al. in MI patients, CRP level in serum rapidly increases within a few hours and this rise is proportional the tissue injury.[12]

The mechanism suggested for increased CRP in MI is that localized inflammation such as myocardial necrosis causes an increase in the hepatic synthesis of CRP and its synthesis rate is proportional to the extent of inflammation.[14]

In our study, there was a positive correlation between salivary and serum hs-CRP in both MI patients and controls. The results were statistically highly significant in both MI patients and controls. This was similar to the studies conducted by Mirzail-Dizgah et al.[15] and Punyadeera et al.[16]

Mirzail-Dizgah et al. studied about salivary and serum hs-CRP in 1^st and 2^nd days of acute MI by collecting both stimulated and unstimulated saliva. They concluded that both stimulated and unstimulated saliva was correlating significantly to the serum, and saliva can be used as an alternative diagnostic tool in the detection of acute MI.[16] The study by Punyadeera et al. was the first to conduct a reference range for saliva in healthy controls and cardiac patients. According to their study, the mean salivary hs-CRP in the cardiac population was 727 pg/ml.[16] In the present study, the mean salivary values of hs-CRP in MI were 1519.53 pg/ml. This difference in mean values could be because of inclusion of patients with acute MI and the collection of samples within 48 h. Since saliva and serum were positively correlated in MI patients in our study, saliva can also be used as an alternative fluid to assess the hs-CRP level instead of serum. The limitation of this study is that a larger sample size is needed to correlate the salivary and serum hs-CRP and to confirm the role of saliva as an alternative biofluid to serum. Instead of taking the samples only at baseline levels in patients having MI, if taken at different intervals during the course of the disease, it could predict the progression and outcome of the disease.

SUMMARY

Saliva can be used as an alternative biofluid to determine hs-CRP in MI patients, which is a noninvasive tool in clinical investigations.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.