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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 20  |  Issue : 1  |  Page : 1-7

Evaluation of serum sodium levels and mean platelet volume in children with community-acquired pneumonia


1 Department of Pediatrics and Neonatology, Faculty of Medicine, Al-Azhar University, Assiut, Egypt
2 Department of Chest Diseases, Faculty of Medicine, Al-Azhar University, Assiut, Egypt
3 Department of Clinical Pathology, Faculty of Medicine, Al-Azhar University, Assiut, Egypt

Date of Submission05-Mar-2019
Date of Decision25-May-2019
Date of Acceptance27-Jun-2019
Date of Web Publication4-Mar-2022

Correspondence Address:
Shimaa Esmail Hassen
Departments of Pediatrics and Neonatology
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/AZMJ.AZMJ_40_19

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  Abstract 


Background and aim Community-acquired pneumonia (CAP) is one of the frequent causes of hospital admission, whereas hyponatremia (HN) is a common electrolyte abnormality in hospitalized patients and is associated with considerable morbidity and mortality. Mean platelet volume (MPV) may be a useful predictor for the diagnosis of CAP but not in disease severity. The purpose of this study was to evaluate serum levels of sodium and MPV in a child with CAP.
Patients and methods This is a case–control study that has been carried out in a Malawi General Hospital. The total (100) participants included in the study were classified into two groups as follows: group I which is the case group included 50 children with clinical and laboratory evidence of pneumonia ranging from 1 month to 3 years. Group II which is the control group included 50 children (apparently healthy control) who attended for nonchest problem or serious medical condition. Serum sodium levels, hemoglobin levels, MPV, platelet count, total leukocyte count, and C-reactive protein were done to all children.
Results HN was present in 82% of patients with CAP (41 out of 50). Patients with CAP had lower MPV than their healthy counterparts (7.11±0.42 vs. 9.14±1.04 fl; P<0.001). There was a statistically significant negative correlation between the grade of respiratory distress and the level of serum sodium and a positive correlation between the grade of respiratory distress and MPV (P<0.001).
Conclusion HN is common among hospitalized children with CAP and MPV may be a useful predictor for the diagnosis of CAP.

Keywords: children, mean platelet volume, pneumonia, sodium


How to cite this article:
Hamed AM, Ibrahim MF, Fayed HK, Abd EL-Meguid MM, Hassen SE. Evaluation of serum sodium levels and mean platelet volume in children with community-acquired pneumonia. Al-Azhar Assiut Med J 2022;20:1-7

How to cite this URL:
Hamed AM, Ibrahim MF, Fayed HK, Abd EL-Meguid MM, Hassen SE. Evaluation of serum sodium levels and mean platelet volume in children with community-acquired pneumonia. Al-Azhar Assiut Med J [serial online] 2022 [cited 2022 Jun 29];20:1-7. Available from: http://www.azmj.eg.net/text.asp?2022/20/1/1/339073




  Introduction Top


Community-acquired pneumonia (CAP) is a common and potentially serious illness with considerable morbidity [1]. It is a major cause of morbidity and mortality in children of less than 5 years. Pneumonia is an important cause of morbidity in the developed world, and morbidity and mortality in the developing world [2].

Sodium is one of the most vital electrolytes in the body and is responsible for a number of important functions, mostly related to fluid and water regulation. Sodium is the abundant cation of the extracellular fluid. Levels of serum sodium change in patients with pulmonary infections. The normally accepted range for sodium is 134–145 mEq/l [3].

Hyponatremia (HN, serum sodium <135 mEq/l) is the most common electrolyte imbalance seen in clinical practice, and also in critically ill children. It is usually present in 3% of hospitalized patients. HN can be classified into three groups as mild (131–135 mmol/l), moderate (126–130 mmol/l), and severe (≤125 mmol/l). Mild to moderate HN and severe HN are found in 15–30% and 1–4% of hospitalized patients [4].

The main cause of HN is volume depletion (bleeding, vomiting, diarrhea, and urinary loss), syndrome of inappropriate antidiuretic hormone secretion, congestive heart failure, thiazide diuretics, cirrhosis, renal failure, primary polydipsia, adrenal insufficiency, and hypothyroidism. Several lung disorders, including pneumonia, can cause syndrome of inappropriate antidiuretic hormone through unknown mechanisms [5].

Mean platelet volume (MPV) is a reflection of platelet size, which has been shown to correlate with platelet function and activation [6].

Biochemical markers have been investigated in association with clinical outcome in patients with CAP, including several cytokines such as tumor necrosis factor-α and interleukin 6, C-reactive protein (CRP), procalcitonin, and D-dimer. The role of cytokines as important mediators of lung defense against infections and inflammation is well documented. Cytokines may have either proinflammatory or anti-inflammatory effects depending on a multiple of interacting microbiologic, environmental, and genetic factors that are believed to influence host response to respiratory infections [7].

There is a growing body of clinical proof suggesting that platelets play a crucial role within the inflammatory response. Multiple inflammatory factors such as chemokines, cytokines, and coagulation factors are secreted by platelets [8].

Aim of this study was to evaluate serum sodium levels in patients who were admitted to the hospital with CAP and to evaluate whether MPV could be used as a diagnostic tool of CAP.


  Patients and method Top


This is a case–control study which was conducted during the period from December 2017 to May 2018. The study was approved by the local ethics committee of the University to evaluate and publish information. Written or verbal consent was taken from parents or local guardian. The total number of the study sample was 100 children (aged 1 month to 3 years). The total participants (100) included in the study were classified into two groups as follows: group I is the case group which included 50 children with clinical and laboratory evidence of pneumonia attending the pediatric department and group II included the control group which included 50 children who are apparently healthy control, who attended for nonchest problem or for a serious medical condition.

All included children were chosen according to the following criteria (inclusion criteria): (a) age from 1 month to 3 years, (b) absence of significant illness, and (c) confirmation of the clinical diagnosis of pneumonia by a chest radiograph. Exclusion criteria included (a) neonates (<4 weeks of age) and children more than 3 years of age, (b) children with bronchiolitis, (c) children with a preexisting lung disease, particularly asthma, tuberculosis, and bronchiectasis, (d) children with a congenital heart disease, or a chronic liver or kidney disease, (e) postoperative children, and (f) children who had been hospitalized and treated for 2 or more days before inclusion in the study.

Clinical methods

All cases were subjected to a complete clinical study (through history and physical examination) upon study inclusion, with emphasis on symptoms and signs of pneumonia.

History

Careful history taking include demographic and epidemiological data, for example, age, residence, sex, and smoking by any member in the family.

Symptoms

Fever, cough, dyspnea, and sputum production, although nonrespiratory symptoms such as consciousness alterations, falls, or gastrointestinal symptoms (diarrhea, vomiting).

Signs

Tachypnea, nasal flaring, intercostal retraction, grunting, and cyanosis. The severity of respiratory distress is assessed by Downes’ score [9].

Laboratory methods

The following investigations were performed

Complete blood count, quantitative CRP, and serum sodium level.

Sampling procedure

A measure of 4 ml of venous blood was obtained from each patient by a sterile venipuncture and divided as follows:

One milliliter of venous blood was added to a tube containing EDTA as an anticoagulant for performing complete blood count which included the MPV. One milliliter of blood was added to the empty tube for performing a CRP test. Two milliliters of venous blood allowed clotting for 10–20 min before centrifugation for 20 min at 2000–3000 rpm to remove the supernatant to obtain serum.

Complete blood count assessment including mean platelet volume

It was done by using an automated hematology analyzer Diagon Ltd (Hungary) (D-Cell 60). The volume of the platelets is calculated in femtoliter. A typical range of platelet volumes is 9.7–12.8 fl equivalent to spheres 2.65–2.9 µm in diameter. The normal range is given as 7.5–11.5 fl.

Serum sodium assessment

It was done by using an electrolyte analyzer Sensa Core. The normal blood sodium level is 135–145 mEq/l or 135–145 mmol/l in the international unit.

Quantitative C-reactive protein

It was done by latex agglutination.

Statistical analysis

Data entry and all statistical analyses were performed using the Statistical Package for Social Sciences (SPSS) (New York, USA), version 21, under Windows 7 operating system. The results are expressed as means±SD for quantitative data and by n (%) for qualitative data. Comparisons between the groups were conducted by independent sample t test for parametric data and by Mann–Whitney test for nonparametric data. χ2 test was used to test the significance between groups regarding qualitative data and Fisher’s exact test was used instead of the χ2 test when the expected count in any cell is found to be less than 5.

Receiver operating characteristic (ROC) curve of sodium and MPV was constructed.

The true positive rate (sensitivity) is planned to perform the false positive rate (100-specificity) for various cutoff points. Each point on the ROC curve represents a sensitivity/specificity pair corresponding to a particular decision threshold. The area beneath the ROC curve [area under the curve (AUC)] is a measure of how well a parameter will distinguish between two diagnostic teams (diseased/normal).

P value was assumed as: P value more than 0.05: nonsignificant; P value less than 0.05: significant, and P value less than 0.01: highly significant.


  Results Top


The study population consisted of 100 children, classified into two groups: cases and control group. Each group consisted of 50 children. There was a statistically significant difference between two groups as regards residence (P<0.005), but there was no statistically significant difference as regards age and sex ([Table 1]).
Table 1 Demographic data of the studied groups

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The majority of the cases group is presented by cough (38/50, 76%), expectoration (30/50, 60%), and respiratory distress (50/50, 100%). As regards clinical examination, there was a statistically significant increase in the case group in comparison to the control group in heart rate, respiratory rate, and temperature (P<0.001), but there was no statistically significant difference in weight (P<0.137) ([Table 2] and [Table 3]).
Table 2 Clinical data of the studied groups

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Table 3 Clinical examination of the studied groups

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Laboratory data in both groups including hemoglobin, total leukocyte count, and CRP is presented in [Table 4] with a statistically significant difference between two groups.
Table 4 Laboratory data of studied groups

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HN (serum sodium <135 mmol/l) was present in 41/50 (82%) patients with CAP (the case group); 25 patients had mild HN, 11 patients had moderate HN less than 130 mmol/l, and five patients had severe HN less than 125 mmol/l. The mean±SD of serum sodium concentration in case and control groups were 132.08±4.18 and 139.42±2.57 mmol/l, respectively, with statistically significant difference (P<0.001) ([Table 5]).
Table 5 Mean value of mean platelet volume (fl) and mean value of serum sodium (mmol/l) of the studied groups

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The mean±SD of MPV in case and control groups were 7.11±0.42 and 19.14±1.04 fl, respectively, with statistically significant difference (P<0.001) ([Table 5]).

There was a statistically significant negative correlation between the grade of respiratory distress and mean value of serum sodium and MPV in an earlier stage of respiratory distress but in the late stage, there was a positive correlation between the grade of respiratory distress and MPV (P<0.001) ([Table 6] and [Table 7]).
Table 6 Correlation between grade of respiratory distress and mean value of serum sodium (mmol/l)

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Table 7 Correlation between grade of respiratory distress and mean value of mean platelet volume (fl)

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Cutoff value, AUC, sensitivity, specificity, positive predictive value (PPV), negative predictive value of serum sodium, and MPV of cases versus controls are demonstrated in [Table 8]. Serum sodium and MPV have high sensitivity. So, it can be used in predicting the presence of pneumonia. The ROC curve of sodium and MPV are illustrated in [Figure 1] and [Figure 2].
Table 8 Cut-off value, sensitivity, specificity, positive predictive value, negative predictive value of sodium, and mean platelet volume of cases versus controls

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Figure 1 ROC curve analysis, MPV of cases versus controls. MPV, mean platelet volume; ROC, receiver operating characteristic.

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Figure 2 ROC curve analysis, sodium of cases versus controls. ROC, receiver operating characteristic.

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  Discussion Top


CAP is one in all the foremost common serious infections in kids. It accounts for ∼18% of deaths per year in children fewer than 5 years of age [10].

The WHO estimates that two-thirds of deaths due to pneumonia occur during infancy and more than 90% occur in developing countries. The explanation for the high percentage in developing countries includes overcrowding, malnutrition, low birth weight, and limited access to health services [11]. In Egypt, it was estimated that 10% of deaths below the age of 5 years is likely caused by pneumonia [12].

Sodium is an electrolyte present in all body fluids and is important to traditional body functions. Sodium, along with other electrolytes such as potassium, chloride, and bicarbonate, helps cell functions normally and help regulate the amount of fluid in the body [13]. HN is one of the most commonly diagnosed electrolyte disorders in clinical medicine. As it is often an indicator of an underlying disease, the diagnosis of HN is important in preventing morbidity and mortality [14].

Platelet volume, which is detected at the level of progenitor cells (i.e. the megakaryocyte), is correlated with function and activation of the platelet. The role of MPV as an indicator of platelet function has been investigated in association with several inflammatory disorders such as pneumonia [15]. Pneumonia can be generally accepted as an infectious inflammatory process of the lungs [6].

Regarding the demographic data in our study, there was no statistically significant difference between cases and control groups as regards their age and sex. Our study has shown that 76% of cases presented with a cough which is the most frequent symptom in pneumonia. In agreement with our study, Bennett [16] showed that cough is the most common symptom of pneumonia in infants, along with tachypnea, retractions, and hypoxemia. These may be complained about by congestion, fever, irritability, and decreased feeding.

In our study, vital signs (heart rate, respiratory rate, and temperature) were significantly higher in pneumonic children when compared with healthy controls (P=0.001). In agreement with our study, Bradley et al. [17] reported that tachypnea seems to be the most significant clinical sign. To be measured accurately, the respiratory rate must be counted over a full minute when the child is quiet. In febrile children, the absence of tachypnea has a high negative predictive value (97.4%) for pneumonia [18]. Conversely, the presence of tachypnea in febrile children incorporates a low PPV (20.1%). Fever alone will increase the respiratory rate by 10 breaths/min/°C. In febrile children with tachypnea, the finding of chest retractions, grunting, nasal flaring, and crepitation increases the likelihood of pneumonia. The WHO uses tachypnea in the presence of cough as the diagnostic criterion of pneumonia in developing countries where chest radiography is not readily available [19].

In our study, CRP was significantly higher in cases than controls (P˂0.001) that was comparable to the study of Principi and Espositos [20] and Alcoba et al. [21] who reported that children with high CRP values can be tested using a pneumococcal PCR to rule in the diagnosis of pneumonia with a high PPV.

Our study showed that the serum level of sodium was significantly decreased in the pneumonic patient compared with healthy controls (132.08±4.18 vs. 139.42±2.57) (P=0.001). HN was present in 82% of patients with CAP.

Serum sodium had relatively high specificity which means that it could be used to exclude pneumonia. Serum sodium exhibited high sensitivity which means that it could be used in predicting the presence of pneumonia. ROC curve of sodium showed that the AUC was 0.937 and suggested that serum sodium level cutoff point for making a diagnosis of CAP was 134.3 mmol/l.

In agreement with this study, Karger et al. [22] showed that serum sodium level decreased in the pneumonic patient than those of the control and showed that HN is a common complication present at the time of admission for CAP.The level of HN increased with increasing the degree of respiratory distress (P=0.001). Karki et al. [23] showed that HN among CAP patients at hospital admission was common and the severity of HN increased with increasing the severity of CAP.

Also, Zilberberg et al. [24] showed that HN is common among hospitalized patients with CAP and is associated with worsened clinical and economic outcomes.

Our study showed that MPV significantly decreased in the pneumonic patient compared with healthy control (7.11±0.42 vs. 9.14±1.04) (P=0.001). MPV decreased during the earlier stage of CAP and followed by an increase in MPV in the late stage of CAP.

MPV had relatively high specificity which means that it could be used to exclude pneumonia. MPV exhibited high sensitivity which means that it could be used in predicting the presence of pneumonia. ROC curve of MPV showed that the AUC was 0.984 and suggested that MPV level cutoff point for making a diagnosis of CAP was 7.8 fl.

In agreement with this study Karadag-Oncel et al. [25] showed that patients with CAP had a significantly lower MPV value compared with healthy control and suggested that MPV may be a useful predictor for diagnosing of CAP and patients with more severe disease were found to have significantly higher MPV values compared with patients who are in the early stage of the disease. It may be hypothesized that the bone marrow response to the infection is inadequate in the CAP case in the early stage and that an increase in platelet size only occurred as a result of damage or consumption of peripheral circulating platelets due to hyperstimulation. So, MPV decreased during the earlier stages of CAP and increased in the late stage as a result of bone marrow activation. This was the first study in which the role of MPV as a diagnostic factor for CAP had been evaluated.

The limitation of the study was the small sample size; the cases were taken from a single center and further investigation with serum and urine osmolality and urine sodium could not be done because the facility was not available in this hospital.

Our study recommended that MPV and serum sodium level, in addition to other laboratory investigations, can be used to diagnose CAP and its severe morbidity and mortality can be avoided by early diagnosis and proper treatment.

Conclusions and recommendation

HN was frequently reported in children with CAP. The degree of HN seems to be associated with the severity of CAP. Similarly, serum sodium should be strictly checked at admission and steps need to be carried out immediately for better outcome of the patients. Also, our study suggested that MPV may be a useful predictor for the diagnosis of CAP but not in disease severity. Sodium serum level and MPV are decreased with increasing the grade of respiratory distress.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]



 

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