Differential diagnosis between community-acquired pneumonia and non-pneumonia diseases of the chest in the emergency ward

Diagnostic accuracy of point-of-care tests for acute respiratory infection: a systematic review of reviews

Background

Acute respiratory infections are a common reason for consultation with primary and emergency healthcare services. Identifying individuals with a bacterial infection is crucial to ensure appropriate treatment. However, it is also important to avoid overprescription of antibiotics, to prevent unnecessary side effects and antimicrobial resistance. We conducted a systematic review to summarise evidence on the diagnostic accuracy of symptoms, signs and point-of-care tests to diagnose bacterial respiratory tract infection in adults, and to diagnose two common respiratory viruses, influenza and respiratory syncytial virus.

Methods

The primary approach was an overview of existing systematic reviews. We conducted literature searches (22 May 2023) to identify systematic reviews of the diagnostic accuracy of point-of-care tests. Where multiple reviews were identified, we selected the most recent and comprehensive review, with the greatest overlap in scope with our review question. Methodological quality was assessed using the Risk of Bias in Systematic Reviews tool. Summary estimates of diagnostic accuracy (sensitivity, specificity or area under the curve) were extracted. Where no systematic review was identified, we searched for primary studies. We extracted sufficient data to construct a 2 × 2 table of diagnostic accuracy, to calculate sensitivity and specificity. Methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies version 2 tool. Where possible, meta-analyses were conducted. We used GRADE to assess the certainty of the evidence from existing reviews and new analyses.

Results

We identified 23 reviews which addressed our review question; 6 were selected as the most comprehensive and similar in scope to our review protocol. These systematic reviews considered the following tests for bacterial respiratory infection: individual symptoms and signs; combinations of symptoms and signs (in clinical prediction models); clinical prediction models incorporating C-reactive protein; and biological markers related to infection (including C-reactive protein, procalcitonin and others). We also identified systematic reviews that reported the accuracy of specific tests for influenza and respiratory syncytial virus. No reviews were found that assessed the diagnostic accuracy of white cell count for bacterial respiratory infection, or multiplex tests for influenza and respiratory syncytial virus. We therefore conducted searches for primary studies, and carried out meta-analyses for these index tests. Overall, we found that symptoms and signs have poor diagnostic accuracy for bacterial respiratory infection (sensitivity ranging from 9.6% to 89.1%; specificity ranging from 13.4% to 95%). Accuracy of biomarkers was slightly better, particularly when combinations of biomarkers were used (sensitivity 80-90%, specificity 82-93%). The sensitivity and specificity for influenza or respiratory syncytial virus varied considerably across the different types of tests. Tests involving nucleic acid amplification techniques (either single pathogen or multiplex tests) had the highest diagnostic accuracy for influenza (sensitivity 91-99.8%, specificity 96.8-99.4%).

Limitations

Most of the evidence was considered low or very low certainty when assessed with GRADE, due to imprecision in effect estimates, the potential for bias and the inclusion of participants outside the scope of this review (children, or people in hospital).

Future work

Currently evidence is insufficient to support routine use of point-of-care tests in primary and emergency care. Further work must establish whether the introduction of point-of-care tests adds value, or simply increases healthcare costs.

Funding

This article presents independent research funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme as award number NIHR159948.

C-reactive protein evaluation in communityacquired pneumonia with comorbid chronic heart failure as criterion of antibiotic prescription

AIM

To prove that diagnostic algorithm based on additional measurement of serum C-reactive protein (CRP) for administration of systemic antibacterial therapy (ABT) to patients with suspected community-acquired pneumonia (CAP) and concomitant chronic heart failure (CHF) does not influence outcomes of disease.

MATERIALS AND METHODS

This open, single-center, randomized, prospective, noninferiority study included 160 adult patients with documented functional class II-IV CHF who had been admitted with a preliminary diagnosis of non-severe CAP. Patients were randomized at 1:1 to two groups; group 1 - with additional measurement of CRP (n=80) and group 2 - with the use of routine diagnostic methods (n=80). In group 1, systemic ABT was administered only when serum CRP was >28.5 mg / l (threshold level of the biomarker calculated at the previous stage of the study); group 2 received a standard treatment. Noninferiority test result for both algorithms was evaluated by the number of patients with clinical success on days 12-14 (primary endpoint). Non-inferiority margin was δ=-13.5 %. In addition secondary endpoints (early clinical response on days 3-5; early in-hospital adverse events (development of complications; admission to intensive care unit (ICU); death), death, recurrent CAP or CHF worsening with readmission at 28 day; mortality at 90 and 180 days) were estimated. Standard statistical tools were used for all intergroup comparisons.

RESULTS

76 patients of each group reached the primary endpoint. Systemic ABT was administered to 51 (67.1 %) patients in group 1 and 76 (100 %) patients in group 2 (p<0.05). Both groups were comparable (p>0.05) regarding all endpoints: clinical success, 70 (92.1 %) vs. 69 (90.8 %), Δ=1.3 % (one-sided 97.5 % CI: - 8.25 % for non-inferiority margin δ=-13.5 %); early clinical response, 66 (86.8 %) vs. 68 (89.5 %); admission to ICU, 1 (1.3 %) vs. 1 (1.3 %); development of complications, 20 (26.3 %) vs. 22 (28.9 %); readmission, 5 (6.6 %) vs. 6 (7.9 %); in-hospital mortality, 2 (2.6 %) vs. 1 (1.3 %), mortality at 28 day, 3 (3.9 %) vs. 2 (2.6 %), at 90 day, 5 (6.6 %) vs. 4 (5.3 %), at 180 day, 8 (10.5 %) vs. 9 (11.8 %) cases, respectively.

CONCLUSION

additional measurement of serum CRP in patients with CHF and suspected non-severe CAP was able to reduce rate of systemic ABT administration without outcomes and prognosis worsening.

The role of serum procalcitonin in the differential diagnosis of pneumonia from pulmonary edema among the patients with pulmonary infiltrates on chest radiography

The aim of this study is to evaluate the usefulness of serum procalcitonin (PCT) as a diagnostic biomarker for distinguishing pneumonia from pulmonary edema in patients presenting with pulmonary infiltrates on chest radiography.A comparative study was performed retrospectively in a university-affiliated hospital, from May, 2013 to April, 2015. Adult patients (≥18 years) who showed pulmonary infiltrates on chest radiography and had blood tests with C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), PCT, and N-terminal pro-b-type natriuretic peptide (NT-proBNP) on admission were included in the study. Clinical parameters collected on admission were compared between the case group (n = 143) with pneumonia and the control group (n = 88) with pulmonary edema alone.During the study period, a total of 1217 patients were identified. Of them, a total of 231 patients were included in analyses based on exclusion criteria. In the multivariate logistic regression analysis, PCT ≥0.25 ng/mL, ESR ≥35 mm/h, CRP ≥18 mg/L, NT-proBNP ≤200 pg/mL, underlying neurologic diseases, fever, sputum, absence of cardiomegaly, and a low Charlson comorbidity index were independently associated with pneumonia. For this model, the sensitivity, specificity, positive predictive value, and negative predictive value in distinguishing between the 2 groups were 90.2%, 79.6%, 87.8%, and 83.3%, respectively, with an area under the curve of 0.93.This study suggests that the practical use of PCT in conjunction with clinical data can be valuable in the differential diagnosis of pulmonary infiltrates and guidance for clinicians to prevent antibiotic misuse.

Pneumonia and inflammation in acute decompensated heart failure: a registry-based analysis of 1939 patients

Background:

The prognostic impact of pneumonia and signs of systemic inflammation in patients with acute decompensated heart failure (ADHF) has not been fully elucidated yet. The aim of the present study was thus to investigate the association of pneumonia and the inflammation surrogate C-reactive protein with all-cause mortality in patients admitted for ADHF.

Methods:

We analysed data of 1939 patients admitted for ADHF. Patients were dichotomised according to the presence or absence of pneumonia. The primary endpoint of all-cause mortality was determined by death registry linkage.

Results:

In total, 412 (21.2%) patients had concomitant pneumonia. Median C-reactive protein levels were higher in patients with compared to patients without pneumonia (24.9 versus 9.8 mg/l, respectively; P<0.001). All-cause mortality was significantly higher in patients with pneumonia ( P<0.001). In adjusted Cox regression models, pneumonia as well as C-reactive protein were independently associated with in-hospital mortality. Only C-reactive protein remained as independent predictor for long-term mortality.

Conclusion:

Pneumonia is relatively common in ADHF and a predictor for in-hospital mortality. However, inflammation in general seems to be more important than pneumonia itself for long-term prognosis. Compared to community-acquired pneumonia studies, C-reactive protein levels were rather low and therefore pneumonia might be over-diagnosed in ADHF patients.

The Usefulness of the Delta Neutrophil Index for Predicting Superimposed Pneumonia in Patients with Acute Decompensated Heart Failure in the Emergency Department

Background

Although respiratory infections, such as pneumonia, have long been recognized as precipitators of exacerbation in patients with acute decompensated heart failure (ADHF), identifying signs of concomitant pneumonia in ADHF is a clinical diagnostic challenge. We evaluated the predictive value of the delta neutrophil index (DNI), a new indicator for immature granulocytes, for diagnosing superimposed pneumonia in patients presenting with ADHF in the emergency department (ED).

Methods

This was a retrospective and observational study of consecutive patients (>18 years old) diagnosed with an ADHF in the ED over a 7-month period. Patients were categorized into either the ADHF group or the ADHF with pneumonia group. DNI, serum white blood cell (WBC), C-reactive protein (CRP), and β-natriuretic peptide (BNP) were measured upon ED arrival.

Results

The ADHF with pneumonia group included 30 patients (20.4%). Median initial DNI, WBC, and CRP were significantly higher in the ADHF with pneumonia group [0% vs. 1.8%, p<0.001, 8,200 cells/mL vs. 10,470 cells/mL, p<0.001, and 0.56 mg/dL vs. 6.10 mg/dL, p<0.001]. Multiple logistic regression analyses showed that only initial DNI significantly predicted the presence of superimposed pneumonia in patients with ADHF. In the receiver operating characteristic curves for initial DNI, WBC, and CRP for differentiating superimposed pneumonia in ADHF patients, the area under curve (AUC) of DNI (0.916 [95% confidence interval 0.859–0.955]) was good. AUC of DNI was significantly higher than AUC of CRP and WBC [0.828 and 0.715] (DNI vs. CRP, p = 0.047 and DNI vs. WBC, p<0.001).

Conclusions

Initial DNI, which was measured upon ED arrival, was significantly higher in the ADHF with pneumonia group than in the ADHF group. The initial DNI’s ability of prediction for ADHF with superimposed pneumonia in the ED was good and it was better than those of serum WBC and CRP. Therefore, DNI may serve as a convenient and useful marker for early diagnosis of superimposed pneumonia in patients with ADHF in the ED.

The Diagnostic Value of Serum C-Reactive Protein for Identifying Pneumonia in Hospitalized Patients with Acute Respiratory Symptoms

Background. The clinical diagnosis of pneumonia is sometimes difficult since chest radiographs are often indeterminate. In this study, we aimed to assess whether serum C-reactive protein (CRP) could assist in identifying patients with pneumonia. Methods. For one winter, all consecutive patients with acute respiratory symptoms admitted to the emergency ward of a single center were prospectively enrolled. In addition to chest radiographs, basic laboratory tests, and microbiology, serum levels of CRP were measured at entry. Results. A total of 923 (62.3%) of 1473 patients hospitalized for acute respiratory symptoms were included. Subjects with a final diagnosis of pneumonia had higher serum CRP levels (median 187 mg/L) than those with exacerbations of chronic obstructive pulmonary disease (63 mg/L) or acute bronchitis (54 mg/L, p < 0.01). CRP was accurate in identifying pneumonia (area under the curve 0.84, 95% CI 0.82-0.87). The multilevel likelihood ratio (LR) for intervals of CRP provided useful information on the posttest probability of having pneumonia. CRP intervals above 200 mg/L were associated with LR+ > 5, for which pneumonia is likely, whereas CRP intervals below 75 mg/L were associated with LR < 0.2, for which pneumonia is unlikely. Conclusion. Serum CRP may be a useful addition for diagnosing pneumonia in hospitalized patients with acute respiratory symptoms.

Markers of lower respiratory tract infections in emergency departments

Background

Acute respiratory tract infections are the common causes for admission to emergency department. Appropriate diagnosis and initiating treatment on time are important for reducing morbidity and mortality rate due to lower respiratory tract infection (LRTI). The aim of this study is to determine if C-reactive protein (CRP) levels and white blood cells (WBC) count are considerable markers to help rapid diagnosis and prediction of antibiotic need for lower respiratory infections in emergency departments. The relationships between infectious agents and those markers have also been evaluated.

Methods

Study subjects and control group were selected by defined criteria. Patients were analyzed and assessed for CRP and WBC, sputum Gram stain and culture besides routine laboratory tests and chest X-Rays.

Results

One hundred and ninety four episodes out of 175 patients were evaluated for the study. CRP level and WBC count were detected significantly higher in patients ofstudy group than in those of control group. Pseudomonas aeruginosa and Haemophilus influenzae were the pathogens most often isolated.

Conclusion

In conclusion, CRP and WBC sputum are important markers for diagnosis of LRTI at the emergency departments and results of microbiological analysis of respiratory specimens were correlated with these markers.

Trial registration

Registation number of ethic committee of Dr. Suat Seren Chest Diseases and Surgery Training and Research Hospital: 28.04.2006/114

How to reduce antibiotic consumption for community-acquired pneumonia?

BACKGROUND

The difficulty to diagnose community-acquired pneumonia (CAP) and the lack of scientific data regarding the optimal duration of antibiotic therapy are responsible for overprescribing antibiotics.

OBJECTIVE

The authors had for objective to perform a systematic review of the international medical literature on strategies aimed at reducing antibiotic consumption for CAP.

METHODS

We performed a Pubmed search using the keywords CAP, antibiotic use, duration of antibiotic therapy, procalcitonin, short-course treatment, and biomarkers. We then made a critical review of the selected articles.

RESULTS

Our review identified two strategies used to reduce antibiotic consumption for CAP. The first one was based on procalcitonin (PCT) use. This strategy, even though reducing the duration of antibiotic therapy, does not seem optimal since it is associated with longer antibiotic treatment than recommended by the Infectious Diseases Society of America. Moreover, this strategy is associated with an increased cost in biochemical tests. The other strategy is based on a 2-step clinical reassessment: 1) during the first 24 hours of hospitalization, to confirm the diagnosis of CAP and 2) during hospitalization, to shorten the duration of antibiotic therapy according to the patient's clinical status.

CONCLUSION

Clinical reassessment, currently little studied compared to PCT guidance algorithm, seems to be promising to reduce antibiotic consumption for CAP. Especially since it was never compared to PCT guidance strategy in a randomized clinical trial.

Predictors of cardiogenic and non-cardiogenic causes in cases with bilateral chest infiltrates

Background

Differentiating cardiogenic pulmonary edema from other bilateral lung diseases such as pneumonia is frequently difficult. We conducted a retrospective study to identify predictors for cardiogenic pulmonary edema and non-cardiogenic causes of bilateral lung infiltrates in chest radiographs.

Methods

The study included patients who had newly developed bilateral lung infiltrates in chest radiographs and patients who underwent echocardiography. Cases were divided into two groups based on the echocardiographic findings: the cardiogenic pulmonary edema group and the non-cardiogenic group. Clinical characteristics and basic laboratory findings were analyzed to identify predictors for differential diagnosis between cardiogenic and non-cardiogenic causes of bilateral chest infiltrates.

Results

We analyzed 110 subjects. Predictors of cardiogenic pulmonary edema were higher brain natriuretic peptide (BNP) levels, lower C-reactive protein (CRP) levels on the day of the event (<7 mg/dL), age over 60 years, history of heart disease, and absence of fever and sputum. CRP on the day of the event was an independent factor to differentiate cardiogenic and non-cardiogenic causes of newly developed bilateral chest infiltrates. Also, the validity was comparable to BNP.

Conclusion

Clinical symptoms (sputum and fever), medical history (dyslipidemia and heart disease), and laboratory findings (BNP and CRP) could be helpful in the differential diagnosis of patients with acute bilateral lung infiltrates in chest radiographs.

C-reactive protein for discriminating treatment failure from slow responding pneumonia

BACKGROUND

The management of patients with community-acquired pneumonia (CAP) who fail to improve constitutes a challenge for clinicians. This study investigated the usefulness of C-reactive protein (CRP) changes in discriminating true treatment failure from slow response to treatment.

METHODS

This prospective multicenter observational study investigated the behavior of plasma CRP levels on days 1 and 4 in hospitalized patients with CAP. We identified non-responding patients as those who had not reached clinical stability by day 4. Among them, true treatment failure and slow response situations were defined when initial therapy had to be changed or not after day 4 by attending clinicians, respectively.

RESULTS

By day 4, 78 (27.4%) out of 285 patients had not reached clinical stability. Among them, 56 (71.8%) patients were cured without changes in initial therapy (mortality 0.0%), and in 22 (28.2%) patients, the initial empirical therapy needed to be changed (mortality 40.9%). By day 4, CRP levels fell in 52 (92.9%) slow responding and only in 7 (31.8%) late treatment failure patients (p<0.001). A model developed including CRP behavior and respiratory rate at day 4 identified treatment failure patients with an area under the Receiver Operating Characteristic curve of 0.87 (CI 95%, 0.78-0.96).

CONCLUSION

Changes in CRP levels are useful to discriminate between true treatment failure and slow response to treatment and can help clinicians in management decisions when CAP patients fail to improve.

Role of C-reactive protein and procalcitonin in differentiation of tuberculosis from bacterial community acquired pneumonia

BACKGROUND/AIMS

We investigated the utility of serum C-reactive protein (CRP) and procalcitonin (PCT) for differentiating pulmonary tuberculosis (TB) from bacterial community-acquired pneumonia (CAP) in South Korea, a country with an intermediate TB burden.

METHODS

We conducted a prospective study, enrolling 87 participants with suspected CAP in a community-based referral hospital. A clinical assessment was performed before treatment, and serum CRP and PCT were measured. The test results were compared to the final diagnoses.

RESULTS

Of the 87 patients, 57 had bacterial CAP and 30 had pulmonary TB. The median CRP concentration was 14.58 mg/dL (range, 0.30 to 36.61) in patients with bacterial CAP and 5.27 mg/dL (range, 0.24 to 13.22) in those with pulmonary TB (p<0.001). The median PCT level was 0.514 ng/mL (range, 0.01 to 27.75) with bacterial CAP and 0.029 ng/mL (range, 0.01 to 0.87) with pulmonary TB (p<0.001). No difference was detected in the discriminative values of CRP and PCT (p=0.733).

CONCLUSIONS

The concentrations of CRP and PCT differed significantly in patients with pulmonary TB and bacterial CAP. The high sensitivity and negative predictive value for differentiating pulmonary TB from bacterial CAP suggest a supplementary role of CRP and PCT in the diagnostic exclusion of pulmonary TB from bacterial CAP in areas with an intermediate prevalence of pulmonary TB.

C-reactive protein to distinguish pneumonia from acute decompensated heart failure

BACKGROUND

Patients with acute decompensated heart failure (ADHF) are frequently treated with unnecessary antibiotics since they are confused with pneumonia patients.

AIM

To study the efficacy of measuring C-reactive protein (CRP) levels on admission and CRP velocity in differentiating ADHF from pneumonia.

METHODS

A retrospective observational study of ADHF and pneumonia patients admitted to a tertiary hospital during 2 years. Patients who were already treated with antibiotics on admission were excluded. Efficacy of CRP as a diagnostic marker was evaluated by using receiver operator curves (ROC).

RESULTS

Overall, 72 ADHF and 50 pneumonia patients were included in the study. The mean CRP levels on admission were 13.5+/-13.5 mg/L for the ADHF patients and 127+/-84 mg/L for the pneumonia patients (p<0.001). CRP increases of > or =0.56 mg/L/h were diagnostic of pneumonia. CRP levels on admission together with CRP increases had a sensitivity of 0.96 and a specificity of 0.972 (p<0.001) as markers to distinguish pneumonia from ADHF.

CONCLUSIONS

This study emphasizes the dynamic nature of biomarkers. Demonstrating the efficiency of repeated CRP measurements in an acute setting will provide clinicians with a valuable tool for establishing the correct diagnosis and refraining from unnecessary use of antibiotics.

[Critical evaluation and predictive value of clinical presentation in out-patients with acute community-acquired pneumonia]

Diagnostic probability of community-acquired pneumonia (CAP) depends on data related to age and clinical and radiological findings. The critical evaluation of data in the literature leads to the following conclusions: 1) the prevalence of CAP in a given population with acute respiratory disease is 5% in outpatients and 10% in an emergency care unit. This could be as low as 2% in young people and even higher than 40% in hospitalized elderly patients; 2) the collection of clinical data is linked to the way the patient is examined and to the expertise of the clinician. The absolute lack of "vital signs" has a good negative predictive value in CAP; presence of unilateral crackles has a good positive predictive value; 3) there is a wide range of X-ray abnormalities: localized alveolar opacities; interstitial opacities, limited of diffused. The greatest radiological difficulties are encountered in old people with disorders including chronic respiratory or cardiac opacities and as a consequence of the high prevalence of bronchopneumonia episodes at this age; 4) among patients with lower respiratory tract (LRT) infections, the blood levels of leukocytes, CRP and procalcitonine are higher in CAP patients, mainly when their disease has a bacterial origin. Since you have not a threshold value reliably demonstrated in large populations with LRT infections or acute respiratory disease, presence or absence of these parameters could only be taken as a slight hint for a CAP diagnosis.

Impact of antibiotic restrictions: the physician's perspective

In recent years, there have been worldwide efforts to reduce inappropriate antibiotic prescribing. This has mainly been in response to mounting concerns about the emergence of antimicrobial resistance. Surprisingly, there has been little systematic investigation of the impact of antibiotic restrictions on the complications of infection. It is difficult to address this question using randomised clinical trials in light of the often limited numbers of patients that can be included, who are also often atypical of the broad population of patients receiving antibiotic therapy. Observational data from the UK indicate an association between recent reductions in antibiotic prescribing for lower respiratory tract infection in general practice and an increase in pneumonia mortality. These studies suggest a need for further investigations examining the changing patterns of antibiotic prescribing and their effects on patient outcomes in other countries and in other common infectious diseases. Such studies may provide a useful comparison with the changes observed in lower respiratory tract infection in the UK, and could help to improve antibiotic prescribing practices worldwide. It is also important to study whether associated worse outcomes are limited to certain at-risk groups who should be targeted for care.

[Community-acquired pneumonia]

Diagnostic tools are essential for the physician to reach a correct diagnosis of community-acquired pneumonia, to determine the pathogen, and to estimate the prognosis of individual patients. X-ray of the chest remains the "gold standard" for identification of pneumonia. Modern inflammatory markers such as C-reactive protein and in the future procalcitonin are essential for the differential diagnosis and follow-up. The microbiology tests include, besides classic bacterial cultures, urinary antigen tests for Streptococcus pneumoniae and Legionella pneumophila. A simple prognostic score has been developed to help the physician to decide if the patient needs hospitalization.

Performance of a bedside C-reactive protein test in the diagnosis of community-acquired pneumonia in adults with acute cough

PURPOSE

To evaluate the performance of a rapid, bedside whole blood C-reactive protein test as a diagnostic test for pneumonia in adults.

METHODS

We enrolled consecutive adults who presented with acute cough (duration < or =3 weeks). A fingerstick blood specimen for C-reactive protein level was obtained. Patients also provided information about demographic characteristics and symptoms. Physical examination findings, diagnoses, and treatments were abstracted from the medical record; illness duration and subsequent office visits were determined with follow-up telephone calls. A clinical prediction rule for pneumonia was calculated for each patient and compared with C-reactive protein levels.

RESULTS

Twenty (12%) of the 168 patients in the study had radiographic evidence of pneumonia. Median C-reactive protein levels were significantly higher for patients with pneumonia than in the remaining patients (60 mg/L vs. 9 mg/L, P <0.0001). The area under the receiver operating characteristic (ROC) curve for C-reactive protein level as a predictor of pneumonia was 0.83. C-reactive protein level and the clinical prediction rule were independently associated with pneumonia, yielding a combined area under the ROC curve of 0.93. C-reactive protein level was not associated with hospitalization or resolution of symptoms.

CONCLUSION

C-reactive protein levels could be a valuable addition to clinical prediction rules for pneumonia. A C-reactive protein level > or =100 mg/L might be a useful indication for chest radiography or empiric antibiotic therapy when the diagnosis of pneumonia is in doubt.

Contribution of C-Reactive Protein to the Diagnosis and Assessment of Severity of Community-Acquired Pneumonia

STUDY OBJECTIVE

To assess the usefulness of serum C-reactive protein (CRP) in the diagnosis and treatment approach of patients with community-acquired pneumonia (CAP).

DESIGN

Population-based case-control study.

SETTING

A mixed residential-industrial urban area of 74,368 adult inhabitants in the Maresme region (Barcelona, Spain).

PATIENTS

From December 1993 to November 1995, all subjects who were > 14 years of age, were living in the area, and had received a diagnosis of CAP, which had been confirmed by chest radiographs and compatible clinical outcome, were registered. Patients from residential care facilities were excluded. Serum samples were assayed for CRP in the acute phase of the disease. Data from 201 patients with CAP were compared with 84 healthy control subjects matched by age, sex, and municipality, as well as with 25 patients with initially suspected pneumonia that was not confirmed at follow-up. Median CRP levels were 110.7, 1.9, and 31.9 mg/L, respectively. The thresholds of the test for discriminating among these three groups of subjects were 11.0 and 33.15 mg/L.

RESULTS

Eighty-nine patients (44.8%) had an identifiable etiology. The most common pathogens were Streptococcus pneumoniae, viruses, and Chlamydia pneumoniae, followed by Mycoplasma pneumoniae, Legionella pneumophila, and Coxiella burnetii. There were statistically significant differences in the median CRP levels in pneumococcal (166.0 mg/L) and L pneumophila (178.0 mg/L) etiologies compared to other causative pathogens. Lower levels of CRP were found in pneumonia caused by viruses and C burnetii as well as in negative microbiological findings. The median CRP levels in hospitalized patients were significantly higher than in outpatients (132.0 vs 76.9 mg/L, respectively; p < 0.001). Considering a cut point of 106 mg/L in men and 110 mg/L in women for deciding about the appropriateness of inpatient care, CRP levels showed a sensitivity of 80.51% and a specificity of 80.72%.

CONCLUSIONS

Serum CRP level is a useful marker for establishing the diagnosis of CAP in adult patients with lower respiratory tract infections. High CRP values are especially high in patients with pneumonias caused by S pneumoniae or L pneumophila. Moreover, high CRP values are suggestive of severity, which may be of value in deciding about the appropriateness of inpatient care.

Reactantes de fase aguda en la neumonía adquirida en la comunidad

BACKGROUND AND OBJECTIVE

We aimed to study the usefulness of acute-phase proteins in the evolution and microbial diagnosis of community-acquired pneumonia (CAP).

PATIENTS AND METHOD

One-year prospective study of CAP. Plasma levels of C reactive protein (CRP), erythrocyte sedimentation rate (ESR) and fibrinogen were measured on admission in all patients with CAP.

RESULTS

240 cases of CAP were included in the study. ESR was higher in patients who developed pleural effusion (p = 0.03). A value of ESR > 120 mm/h was associated with a higher likelihood of having a CAP complicated with pleural effusion (odds ratio = 3.80; 95% confidence interval, 1.37-10.49, p = 0.006). Baseline concentrations of CRP, ESR and fibrinogen were higher in patients who developed empyema. CRP and fibrinogen levels were significantly higher in patients with Legionella pneumophila pneumonia, while pneumococcal pneumonia was associated with a higher ESR value.

CONCLUSIONS

Some frequently used acute-phase proteins can be useful in the prediction of pleural complications and in the approach to the etiological diagnosis of CAP.