Carditis is the most important manifestation of rheumatic fever and may result in significant morbidity and mortality as it can lead to chronic rheumatic heart disease. Although rheumatic fever is a multisystemic disease, the most common cause of mortality and morbidity is cardiac involvement, which can encompass the endocardium, myocardium and/or pericardium. The most commonly affected valves in rheumatic fever are the mitral and aortic valves. Cardiac involvement may progress from asymptomatic mild valvulitis to severe mitral and/or aortic insufficiency causing cardiac failure. Reference Giray and Hallioglu1–Reference Rhodes, Rasa and Yamamoto4 The exact mechanism of carditis is unclear, although it is known as an inflammatory and autoimmune disease. The development of autoimmunity in sensitive individuals causes inflammation and damage to the heart valves. Reference Giray and Hallioglu1
Some studies have correlated specific markers with the severity of valvular involvement in patients with rheumatic carditis. Recently, it was found that inflammatory cytokines played a significant role in the pathogenesis of rheumatic fever. In addition, significantly increased cytokine, nitrite and adrenomedullin levels were detected in the sera of patients with rheumatic fever. Lymphocyte accumulation, overexpression of adhesion molecules and complement deposition in heart tissues have also been shown. These measured markers, including neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio and mean platelet volume, are accepted as novel indicators of continuing inflammation in rheumatic fever. Neutrophil-to-lymphocyte ratio has become increasingly important as an inflammatory marker in recent years. New findings have shown that platelets are not only involved in haemostasis but also constitute an important component of the inflammatory response. Mean platelet volume indicates platelet size and the rate of platelet production in bone marrow and can be used as a marker of severity of inflammation and platelet activation. A low mean platelet volume is usually related to an inflammatory state. Reference Kucuk, Ozdemir and Karadeniz3,Reference Celik and Celik5,Reference Karpuz, Giray, Ozyurt, Bozlu, Unal and Hallioglu6
To our knowledge, no study has been conducted on the correlation of neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio and mean platelet volume with severity of carditis in rheumatic fever at Sanglah Hospital, Denpasar. Our study thus aimed to investigate the correlation of neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio and mean platelet volume with severity of carditis in children with rheumatic fever.
Methods
This was a retrospective, cross-sectional study conducted between January 2018 and December 2020 at Sanglah General Hospital, Bali. The subjects of this study were children aged 5–18 years with rheumatic fever admitted to Sanglah Hospital during the study period. Inclusion criteria were children 5–18 years of age with a diagnosis of rheumatic fever based on the 2015 Jones criteria. Exclusion criteria were incomplete medical records and a diagnosis of rheumatic heart disease, which was based on evidence of permanent heart valve damage secondary to acute rheumatic fever according to the 2012 World Heart Federation Criteria. Reference Kumar, Antunes and Beaton7 The sample size of this study was 45 patients.
Severity of carditis was characterised by a clinical, audible murmur during physical examination and demonstration of valvular involvement by echocardiography and classified as without, mild, moderate or severe carditis. Echocardiography was evaluated by two paediatric cardiologists. A Kappa coefficient was used to assess inter-rater agreement among paediatric cardiologists.
Mild carditis was defined as mild mitral and/or aortic regurgitation clinically and/or by echocardiography, no clinical evidence of heart failure and no cardiac chamber enlargement on echocardiography. Moderate carditis was defined as any mitral or aortic valve lesion of moderate severity on clinical examination, cardiac chamber enlargement seen on echocardiogram or any mitral or aortic valve lesion graded as moderate on echocardiogram. Mitral regurgitation is a broad, high-intensity proximal jet filling half the left atrium or a lesser volume high-intensity jet producing prominent blunting of pulmonary venous inflow. Aortic regurgitation occurs when the diameter of the regurgitant jet is 15–30% of the diameter of the left ventricular outflow tract with flow reversal of the upper descending aorta. Severe carditis was defined as any impending or previous cardiac surgery, any valve lesion graded as severe on clinical examination, any valve lesion associated with significant cardiomegaly or heart failure, any valve lesion graded as severe on echocardiogram or abnormal regurgitant colour with Doppler flow pattern in pulmonary veins (indicating mitral regurgitation) or Doppler reversal in the lower descending aorta (indicating severe aortic regurgitation). Reference Dougherty, Nascimento, Carapetis, Dougherty, Carapetis, Zuhlke and Wilson8
Type of valve involvement was defined as the valve affected either clinically by detection of a corresponding murmur or subclinically by echocardiography, differentiated by aortic regurgitation, mitral regurgitation or both. Neutrophil-to-lymphocyte ratio was calculated by dividing neutrophil count by lymphocyte count. Platelet-to-lymphocyte ratio was calculated by dividing platelet count by lymphocyte count. Mean platelet volume was defined as platelet size and the rate of platelet production in the bone marrow.
Continuous data are presented as mean and standard deviation if normally distributed or median and range if not normally distributed. Categorical data are presented as percentages. The correlation between parameters was assessed using Spearman’s correlation tests. Correlations adjusted by type of valve involvement were also used to determine the severity of carditis were assessed using multivariate partial correlation analysis. Significant correlations underwent receiver operating characteristic curve analysis to determine the optimum cut-off levels to predict the severity of carditis. A p value of less than 0.05 was considered statistically significant with a 95% confidence interval. All statistical analyses were performed using Statistical Package for Social Sciences software. This study was approved by the Ethics Committee of Sanglah Hospital, Denpasar (number 529/UN14.2.2.V ll.14/LT/2021).
Results
From January 2018 to December 2020, we found 45 patients admitted to Sanglah Hospital. Carditis was present in 40 (88.9%) subjects. The median patient age was 12 years, and the majority of subjects were male (55.6%). The most common clinical manifestations were polyarthritis, arthralgia and fever. Patient demographics, clinical manifestations and laboratory values are listed in Table 1.
Table 1. Characteristics of subjects.
AR=aortic regurgitation; ASO=anti-streptolysin O; CRP=C-reactive protein; ESR=Erythrocyte sedimentation rate; MPV=mean platelet volume; MR=mitral regurgitation; NLR=neutrophil-to-lymphocyte ratio; PLR=platelet-to lymphocyte ratio; SD=standard deviation; WBC=white blood count
The inter-rater agreement for echocardiography in this study was good (Kappa 0.83). Spearman’s correlation analysis showed a strong positive correlation between neutrophil-to-lymphocyte ratio and severity of carditis (r = 0.66, p = 0.001). There was no significant correlation between platelet-to-lymphocyte ratio and severity of carditis (r = 0.23, p = 0.13). There was a very weak negative but not significant correlation between mean platelet volume and severity of carditis (r = −0.01, p = 0.95; Table 2). Using a cut-off of 3.4, neutrophil-to-lymphocyte ratio predicted severe carditis with a sensitivity of 81.8% and specificity of 91.3% in patients with rheumatic fever (receiver operating characteristic area under curve: 0.9, 95% confidence interval: 0.82–0.99; Fig 1). Multivariate partial correlation analysis revealed that type of valve involvement was an independent predictor between neutrophil-to-lymphocyte ratio and severity of carditis (r = 0.49, p = 0.001).
Figure 1. The ROC curve analysis of neutrophil to lymphocyte ratio for predicting severe carditis. AUC=area under curve; CI=confidence interval; NLR=neutrophil to lymphocyte ratio.
Table 2. Correlation between neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and mean platelet volume with severity of carditis.
MPV=mean platelet volume; NLR=neutrophil-to-lymphocyte ratio; PLR=platelet-to lymphocyte ratio
Discussion
This study showed that neutrophil-to-lymphocyte ratio is positively correlated with the severity of carditis in rheumatic fever. Platelet-to-lymphocyte ratio and mean platelet volume were not significantly correlated with the severity of carditis. Moreover, our study showed that a neutrophil-to-lymphocyte ratio > 3.4 predicts the presence of severe carditis with a sensitivity of 81.8% and specificity of 74% in patients with rheumatic fever.
The significance of rheumatic fever is almost solely due to its cardiac sequela. People who have had severe carditis previously are at higher risk of subsequent episodes associated with further cardiac valve damage. Rheumatic heart disease is the most common form of paediatric heart disease in the world and is the leading cause of cardiac death in the first five decades of life.Reference Asik, Duru and Elevli9 Mitral regurgitation ranging from mild to severe was present in 95%, mitral stenosis in 16%, aortic regurgitation in 44% and tricuspid regurgitation in 56% of the patients in our study. More subjects had severe carditis with a combination of mitral regurgitation and aortic regurgitation.
In the case of rheumatic fever, several inflammatory cells infiltrate both the myocardium and the valves. Activated lymphocytes, macrophages, tumour necrosis factor, cytokines and interleukins play an important role in the pathogenesis of carditis in rheumatic fever. Cytokines produced by activated lymphocytes and macrophages after antigenic stimulation can play an important role in the pathogenesis. Previously reported data showed high interleukin (IL)-1 levels in patients with rheumatic fever and rheumatic heart disease. Hafez et al. suggested that IL-1a and IL-6 may be used as a minor criterion in carditis and arthritis, respectively, and anti-cytokine therapy, such as anti-IL-1a or anti-IL-6, has been recommended for preventing and decreasing valvular damage in rheumatic carditis. Another study described IL-1 as a minor criterion for the diagnosis of carditis and IL-6 for the diagnosis of arthritis in patients with rheumatic fever.Reference Asik, Duru and Elevli9
In recent years, there has been a focus on white blood cell subtypes, such as neutrophils and lymphocytes, and neutrophil-to-lymphocyte ratio as predictors of cardiovascular risk. Many studies have shown that high neutrophil-to-lymphocyte ratios are associated with increased inflammation in various cardiovascular diseases. Some studies have correlated neutrophil-to-lymphocyte ratio with the severity of valvular involvement in patients with rheumatic carditis, though other studies comparing neutrophil-to-lymphocyte ratio in patients with newly diagnosed rheumatic fever before and after treatment found no significant differences. In this study, a higher neutrophil-to-lymphocyte ratio correlated with severe carditis. These findings are in line with Celik et al., who found that there was a significant positive correlation between neutrophil-to-lymphocyte ratio and severity of carditis in patients with rheumatic fever. The primary cause of increased neutrophil-to-lymphocyte ratio is likely the increased apoptosis of lymphocytes triggered by the increased inflammatory status in severe carditis. Elevation of neutrophil-to-lymphocyte ratio in inflammatory diseases has also been linked to neutrophilia and relative lymphopenia caused by increased cortisol due to stress.Reference Buyukoflaz and Arslan10,Reference Boyarchuk, Boytsanyuk and Hariyan11
Neutrophils are activated by IL-1 and increase during inflammation. An inflammatory response is characterised by an infiltration of neutrophils at the site of the injured myocardium and the local production of cytokines (IL-1) that can eventually contribute to detrimental cardiac remodelling. IL-1 is produced as a bioactive precursor in most types of cells, particularly in epithelial cells of the mucosa, liver, lung, kidney and heart. The increase in neutrophil-to-lymphocyte ratio thought to result from IL-1 activation thus correlates with severity of carditis.
The other marker of inflammation in rheumatic fever is platelet-to-lymphocyte ratio. Platelets can increase in number in response to various stimuli, such as systemic infection, inflammatory conditions, bleeding and tumours, acting as acute phase reactants and resulting in the overproduction of pro-inflammatory cytokines that stimulate megakaryocytic proliferation and produce a relative thrombocytosis. Lymphocytopenia induced by the systemic inflammatory response reveals a depression in innate cellular immunity as indicated by a marked decrease in T4 helper lymphocytes and an increase in T8 suppressor lymphocytes. Higher platelet counts may reflect underlying inflammation, and lower lymphocyte counts may represent an uncontrolled inflammatory pathway. Platelets are increased by IL-6 stimulation.Reference Giray and Hallioglu1,Reference Asik, Duru and Elevli9,Reference Ozturk, Baygutalp, Bakan, Altas, Polat and Dorman12 Unfortunately, in our study, there was no statistically significant correlation between platelet-to-lymphocyte ratio and severity of carditis. Ozdemir et al. showed higher platelet levels in children with rheumatic fever compared with healthy children. Increased platelet counts in patients with rheumatic fever occur during the acute stage. The cytokine that plays a role in carditis is IL-1, but stimulation of platelets is induced by IL-6. The role of IL-6 in stimulating platelets may be related to platelets not correlating with carditis severity.
Mean platelet volume has been used as a simple marker of severity of inflammation in various studies, but the results have been inconsistent. Sert et al. found that mean platelet volume values in children with rheumatic fever were lower in the acute period compared with healthy controls and that mean platelet volume values were inversely correlated with white blood cell and platelet count before rheumatic fever treatment. Asik et al. compared patients with rheumatic fever with and without carditis and revealed no significant difference between groups in mean platelet volume values. Another study determined high mean platelet volume values in children with rheumatic heart disease, though values were not measured during the acute phase.Reference Ozturk, Baygutalp, Bakan, Altas, Polat and Dorman12,Reference Park, Schoene and Harris13 In addition, Ozdemir et al. showed that mean platelet volume values were not significantly different between acute carditis and control groups.
In agreement with Asik et al., no significant correlation was revealed between mean platelet volume and severity of carditis in our study. Multiple mechanisms may be responsible for the mean platelet volume values seen in patients with rheumatic fever. Decreased mean platelet volume values in conditions in which inflammatory markers increase, which includes the active stage of rheumatic fever, can indicate the severity of the inflammatory process. Overproduction of cytokines such as IL-6, IL-8 and tumour necrosis factor-α in the acute phase can suppress the size of platelets released from bone marrow by affecting megakaryopoiesis. Previous studies have shown that IL-6 causes a decrease in mean platelet volume values in addition to an increase in platelet numbers. Low mean platelet volume values during rheumatic fever attacks can be attributed to IL-6 due to its effect on platelets.Reference Asik, Duru and Elevli9,Reference Polat, Yildiz and Yuksel14–Reference Ozdemir, Karadeniz and Doksoz18 This may be related to the effect of IL-6. Mean platelet volume value was correlated with IL-6 but carditis was correlated with IL-1.
There were limitations of this study, including its retrospective design and inclusion of a relatively small number of patients. This study did not determine cut-off points for neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio and mean platelet volume to predict severe carditis in children with rheumatic fever. Further study is needed with a larger sample size to determine cut-off points for neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio and mean platelet volume for identifying severe carditis.
In conclusion, a significant positive correlation was found between neutrophil-to-lymphocyte ratio and severity of carditis in children with rheumatic fever. In addition, this study showed that platelet-to-lymphocyte ratio and mean platelet volume values do not correlate with severity of carditis. Not only are these indicators inexpensive, simple, rapid and readily available at nearly all healthcare facilities but they are routinely measured as inflammatory markers. The neutrophil-to-lymphocyte ratio can help predict severity of carditis if echocardiography is not performed and can be used as a baseline for therapy.
Acknowledgements
None.
Financial support
The authors received no specific grants from any funding agency in the public, commercial, or non-for-profit sectors.
Conflict of interest
None declared.
