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Research Article

Diagnostic value of urea, creatinine and blood parameters in patients with pneumonia diagnosed with chronic obstructive pulmonary disease

[version 1; peer review: 2 approved with reservations]
PUBLISHED 05 Apr 2019
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Abstract

Background: This study aimed to investigate the diagnostic value of urea, creatinine and other blood parameters in patients with pneumonia diagnosed with chronic obstructive pulmonary disease (COPD) for the first time.
Methods: In this retrospective study, patients who had been diagnosed with COPD for the first time and were diagnosed with pneumonia were included. A total of 193 patients were divided into three groups as COPD + pneumonia (n=123), COPD (n=36) and pneumonia (n=34).
Results: In total, 59 women (48.0%) and 64 men (52.0%) from the COPD + pneumonia group, 13 women (36.1%) and 23 men (63.9%) from the COPD group, 21 women (61.8%) and 13 men (38.2%) from the pneumonia group were assessed. The mean age of the COPD + pneumonia group was 69.58±13.62, 66.28±12.55 for the COPD group and 53.97±19.72 for the pneumonia group. The highest values of C-reactive protein (CRP), urea, creatinine, white blood cells (WBC), neutrophils, eosinophils and hemoglobin were the highest in COPD + pneumonia group. CRP levels were significantly different between COPD + pneumonia group (p<0.05). The parameters urea, WBC and neutrophils were significantly different between COPD + pneumonia group and pneumonia group (p<0.05). There was a statistically significant difference between COPD and pneumonia groups in terms of neutrophils and eosinophils values (p<0.05). According to the results of receiver operating characteristic analysis, the diagnostic value of the urea parameter in determining the COPD + pneumonia group was not statistically significant (p>0.05). On the other hand, the diagnostic value of CRP, WBC and neutrophils values were statistically significant (p<0.05).
Conclusions: Elevation in WBC and neutrophil values in patients diagnosed with pneumonia have an important role in diagnosis of COPD.

Keywords

COPD, Pneumonia, urea, creatinine, blood count

Introduction

Pneumonia has been known since late 1800s, and has been recognized as a major cause of death1. Pneumonia is one of the most common causes of mortality in children under 5 years, and common in South Asia and sub-Saharan Africa; it is a form of acute respiratory tract infection2. The annual incidence of community-acquired pneumonia (CAP) ranges from 5 to 11 per 1000 persons in the United States. It is common in the winter. There are several risk factors associated with CAP, such as neurologic and gastrointestinal abnormalities, male gender, multilobar involvement, high fever, etc.3. CAP is an infection of the pulmonary parenchyma by causative microorganisms4. Streptococcus pneumonia is the leading cause of bacterial pneumonia, causing 30-50% of childhood pneumonia in developing countries5. In diagnosis of the disease, chest X-rays, complete blood count and electrolyte count tests are used5. In treatment of pneumonia, medication and antibiotic therapy are commonly used. A 6-month observation is recommended by the UK National Institute for Health and Care Excellence. In addition, it is important to examine environmental conditions as well as given medication or therapy6. It is reported that smoking, chronic lung diseases, heart disease and diabetes increase the prevalence of disease7.

Chronic obstructive pulmonary disease (COPD) is another common lung disease, characterized by a slow and debilitating progression8. It causes changes in the lungs with airflow restrictions and physical symptoms such as dyspnoea9. Obstructive bronchiolitis and emphysema may represent comorbidities of COPD10,11. There is evidence that inhaled corticosteroids, a treatment for COPD, and increase risk of pneumonia12. In addition, previous research has shown that exacerbation of COPD and pneumonia in COPD has different clinical and analytical properties, although mechanisms are similar12,13.

This study aimed to investigate the diagnostic value of urea, creatinine and some blood parameters in patients with pneumonia that had been diagnosed with COPD for the first time.

Methods

Study participants and eligibility

In this retrospective study, patients who had been diagnosed with COPD for the first time and were diagnosed with Pneumonia and who were admitted to Kadıköy Medicana Hospital, Istanbul, Turkey, between 12 October 2017 and 12 October 2018 were included in the study. A sample of convenience was used, with a voluntary patient consent form. The eligibility criteria were as follows:

  • Previously diagnosed with pneumonia,

  • First diagnosed with COPD,

  • Without a history of clinical intervention in patient epicrisis,

  • Without a malignant disorder

  • Completed patient consent form

A total of 123 patients with pneumonia among 160 patients who met inclusion criteria were included in the study. A total of 193 patients were divided into three groups as COPD + pneumonia (n = 123), COPD (n = 36) and pneumonia (n = 34). In the second group of patients diagnosed with COPD, the patients who were not diagnosed with pneumonia were designated as the first control group, and patients diagnosed with pneumonia and patients who were not diagnosed with COPD was the second control group. Each patient provided written informed consent for their clinical details to be used when admitted; the hospital management granted approval for this study.

Variables assessed in this study

The variables assessed in this study were age, gender, CRP, Urea, Creatine, WBC, NEU, EOS and HGB, which were taken from patient records with approval.

Statistical analysis

The binary and ordinal data were described by frequency analysis and the other measurement parameters by mean and standard deviation values. Kolmogorov-Smirnov analysis was performed to assess normality distribution of the data before the difference analysis. Independent samples t-test was used for the difference of normal distribution between WBC and hemoglobin data. The Mann-Whitney U-test was used to analyze the difference between paired groups (COPD + pneumonia vs COPD only; COPD + pneumonia vs pneumonia only; COPD only vs pneumonia only) of CRP, urea, creatinine, neutrophils and eosinophils parameters which did not conform to normal distribution. Receiver operating characteristics (ROC) analysis was used for CRP, urea, WBC and NEU. All analyses were performed in SPSS 17.0 for Windows, and performed at 95% confidence interval.

Results

Demographic information and clinical values

The distribution of gender, age and some clinical parameters of the case groups included in the study are shown in Table 1.

Table 1. Demographic and clinical parameters of patient groups.

ParameterCOPD + Pneumonia (n=123)COPD (n=36)Pneumonia (n=34)
Female, n (%)59 (48.0)13 (36.1)21 (61.8)
Male, n (%)64 (52.0)23 (63.9)13 (38.2)
Age, (mean ± SD)69.58±13.6266.28±12.5553.97±19.72
CRP, mg/l1.98±3.400.59±1.151.84±2.98
Urea, mg/dl47.13±30.6242.50±30.4534.52±18.32
Creatine, mg/dl0.89±0.350.87±0.460.83±0.36
WBC, ×103/μl8.92±3.557.71±2.237.37±3.01
NEU, ×103/μl6.19±3.435.08±1.944.90±2.44
EOS, ×103/μl0.20±0.220.19±0.140.13±0.11
HGB, g/dl13.54±2.0113.45±1.6312.91±1.68

COPD, chronic obstructive pulmonary disease; CRP, C-reactive protein; WBC, white blood cells; NEU, neutrophils; EOS, eosinophils; HGB, hemoglobin.

In total, there were 59 women (48.0%) and 64 men (52.0%) in the COPD + pneumonia group, 13 women (36.1%) and 23 men (63.9%) in the COPD group, and 21 women (61.8%) and 13 men (38.2%) in the pneumonia group included in the study. The mean age of patients was 70±14 in the COPD + pneumonia group, 66±13 in the COPD group and 54±20 in the pneumonia group. The highest values of CRP, urea, creatinine, WBC, neutrophils, eosinophils and hemoglobin were observed in the COPD + pneumonia group. The results of the differential analysis of the clinical parameters in the study are presented in Table 2. Raw values are available on Open Science Framework14.

Table 2. Difference analysis results between paired groups (COPD + Pneumonia, COPD and Pneumonia) and p-values.

ParameterGroup 1 vs group 2Group 1 vs group 3Group 2 vs group 3
CRPa0.0060.5360.117
Ureaa0.1530.0060.329
Creatinea0.3190.3110.850
WBCb0.0560.0220.592
NEUa0,1370.0330.040
EOSa0.4380.2380.005
HGBb0.8030.0990.182

aMann-Whitney U-test; bindependent samples t-test. Group 1, COPD+pneumonia; group 2, COPD only; group 3, pneumonia only. Figures in bold represent statistically significant differences. CRP, C-reactive protein; WBC, white blood cells; NEU, neutrophils; EOS, eosinophils; HGB, hemoglobin.

Data analysis

According to the results of the difference analysis, there was a statistically significant difference between CRP levels of the COPD + pneumonia and COPD groups (p<0.05). The parameters urea, WBC and neutrophils were significantly different between the COPD + pneumonia and pneumonia groups (p<0.05). There was a statistically significant difference between COPD and pneumonia groups in terms of neutrophils and eosinophils values (p<0.05). The results of ROC analysis of CRP, urea, WBC and neutrophils variables were given as follows.

According to the results of the ROC analysis (Figure 1), the diagnostic value of the urea parameter in determining the COPD + pneumonia group was not statistically significant (p>0.05). On the other hand, the diagnostic value of CRP, WBC and neutrophils values were statistically significant (p<0.05). The distribution of areas under the curve according to ROC analysis is given in Table 3.

3ec629ed-af77-44b1-a3cc-3c8bd2046069_figure1.gif

Figure 1. Receiver operating characteristic analysis results for C-reactive protein (CRP), urea, white blood cells (WBC) and neutrophils (NEU).

Table 3. Receiver operating characteristic analysis results and areas under curves.

Test result variableAreaStandard errorp-valueAsymptotic 95% confidence
interval
Lower boundUpper bound
CRP0.6930.0600.0050.5750.810
Urea0.5960.0680.1630.4620.730
WBC0.6380.0610.0440.5180.758
NEU0.6380.0630.0440.5150.762

CRP, C-reactive protein; WBC, white blood cells; NEU, neutrophil.

The area under the curve was the highest for the CRP value.

Discussion

Pneumonia1517 and COPD1820 are two diseases that are the focus of considerable research into respiratory complaints. In addition, there are studies reporting the distribution of these diseases in different demographic groups2126. In our study, pneumonia was more common in women, whereas COPD was more common in men. In both groups, the gender distributions were similar, although males made up the majority. However, the mean age of patients was the highest in COPD + pneumonia patients.

In patients with COPD and pneumonia, the clinical condition of the patients is poorer than for patients with one or the other conditions, and it is suggested that two diseases trigger each other2534. In our study, urea and creatinine levels were higher in patients with pneumonia who were diagnosed with COPD for the first time. WBC and neutrophil values were statistically higher among patients with COPD than in patients with only pneumonia. The difference in urea, WBC and neutrophil values was not significant between the COPD and COPD + pneumonia groups. It can be said that the increase in these three parameters may have diagnostic implications for COPD in patients with pneumonia.

Conclusion

According to the results of this study, a history of pneumonia aggravates the clinical course of patients with COPD for the first time. On the other hand, the increase in CRP, WBC and neutrophil values in patients diagnosed with pneumonia but not COPD may give the first indication of a possible development of COPD.

According to the results of ROC analysis, CRP is among the most important determinants of patients with the first time diagnosed with COPD and diagnosed with pneumonia. On the other hand, WBC and neutrophil elevation in patients with previously diagnosed pneumonia may also be an important factor in the diagnosis of COPD.

Data availability

Open Science Framework: Diagnostic value of urea, creatinine and blood parameters in patients with pneumonia diagnosed with chronic obstructive pulmonary disease. https://doi.org/10.17605/OSF.IO/Y4V8T14.

This project contains the demographic and clinical variables of patients measured in this study.

Data are available under the terms of the Creative Commons Zero "No rights reserved" data waiver (CC0 1.0 Public domain dedication).

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Akduman S. Diagnostic value of urea, creatinine and blood parameters in patients with pneumonia diagnosed with chronic obstructive pulmonary disease [version 1; peer review: 2 approved with reservations]. F1000Research 2019, 8:388 (https://doi.org/10.12688/f1000research.18538.1)
NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article.
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Open Peer Review

Current Reviewer Status: ?
Key to Reviewer Statuses VIEW
ApprovedThe paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approvedFundamental flaws in the paper seriously undermine the findings and conclusions
Version 1
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PUBLISHED 05 Apr 2019
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Reviewer Report 09 Dec 2019
Elena Titova, Department of Thoracic and Occupational Medicine, Trondheim University Hospital, Trondheim, Norway 
Approved with Reservations
VIEWS 6
This retrospective study is aimed “to investigate the diagnostic value of urea, creatinine and some blood parameters in patients with pneumonia that had been diagnosed with COPD for the first time”.

I would like to make following ... Continue reading
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CITE
HOW TO CITE THIS REPORT
Titova E. Reviewer Report For: Diagnostic value of urea, creatinine and blood parameters in patients with pneumonia diagnosed with chronic obstructive pulmonary disease [version 1; peer review: 2 approved with reservations]. F1000Research 2019, 8:388 (https://doi.org/10.5256/f1000research.20289.r55810)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
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Reviewer Report 30 Oct 2019
Hakan Tanrıverdi, Faculty of Medicine, Bülent Ecevit University, Zonguldak, Turkey 
Approved with Reservations
VIEWS 7
  1. The study population is enough but the control group is to small. Maybe a power is needed.
     
  2. In the abstract section the authors wrote "According to the results of receiver operating characteristic
... Continue reading
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HOW TO CITE THIS REPORT
Tanrıverdi H. Reviewer Report For: Diagnostic value of urea, creatinine and blood parameters in patients with pneumonia diagnosed with chronic obstructive pulmonary disease [version 1; peer review: 2 approved with reservations]. F1000Research 2019, 8:388 (https://doi.org/10.5256/f1000research.20289.r55807)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.

Comments on this article Comments (0)

Version 1
VERSION 1 PUBLISHED 05 Apr 2019
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Alongside their report, reviewers assign a status to the article:
Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions
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