C-reactive protein in diagnosis of community-acquired pneumonia in adult patients in primary care

Impact of Lung Ultrasound along with C-Reactive Protein Point-of-Care Testing on Clinical Decision-Making and Perceived Usefulness in Routine Healthcare for Patients with Lower Respiratory Tract Infections: Protocol for Analytical Observational Study

Background: Lower respiratory tract infections (LRTIs) are a significant cause of primary care consultations. Differentiating between viral and bacterial infections is critical for effective treatment and to minimize unnecessary antibiotic use. This study investigates the impact of combining lung ultrasound (LUS) with capillary blood C-reactive protein (CRP) rapid testing on clinical decision-making for patients with LRTIs. Objectives: The primary objective is to assess how the integration of CRP testing and LUS influences antibiotic prescription decisions. The study aims to quantify the percentage change in antibiotic prescriptions before and after performing LUS, following history taking, clinical examination, and CRP testing. Methods: This analytical observational study will be conducted in six primary care centers within the Health Region of Lleida, Catalonia, serving a mixed urban and rural population of approximately 105,000 residents. The study will recruit 196 patients aged 18 and over, presenting with LRTI symptoms and not treated with antibiotics in the preceding 14 days. Participants will undergo CRP testing followed by LUS during their consultation. Statistical analyses, including linear regression, bivariate analysis, Pearson or Spearman correlation, and logistic regression, will be used to evaluate the impact of LUS on clinical decisions and its predictive value in diagnosing bacterial infections. Results and Conclusions: This study will provide insights into the role of LUS combined with CRP testing in improving diagnostic accuracy and guiding antibiotic prescription decisions in primary care. The findings aim to enhance treatment protocols for LRTIs, reducing unnecessary antibiotic use and improving patient outcomes.

C-reactive protein influences the doctor's degree of suspicion of pneumonia in primary care: a prospective observational study

BACKGROUND

In primary care, the diagnosis of pneumonia is often based on history and clinical examination alone. However, a previous study showed that the general practitioner's degree of suspicion correlates well with findings on chest X-ray, when the C-reactive protein (CRP) value is known.

OBJECTIVES

The present study aimed to investigate to what extent the physician's degree of suspicion is affected by the CRP level when community-acquired pneumonia is suspected in primary care.

METHODS

A prospective observational study was conducted at five primary health care centres in Sweden between October 2015 and December 2017. Adult patients (n = 266) consulting their health care centre with symptoms of lower respiratory tract infection, where the physician suspected pneumonia, were included consecutively. Anamnestic information and findings from clinical examination were documented in a case report form. All patients were tested for CRP. The physicians rated their degree of suspicion as 'unsure,' 'quite sure,' and 'sure' before and after the CRP result.

RESULTS

The degree of suspicion of pneumonia changed in 69% of the cases; most often to a lower degree (40%). In 28% of the cases, there was no longer any suspicion of pneumonia after CRP.

CONCLUSION

Our results indicate that CRP testing highly influences the physician's degree of suspicion of pneumonia in primary care and that it seems to be of most value when not sure of the diagnosis.

Change in the use of diagnostic tests in the management of lower respiratory tract infections: a register-based study in primary care

Background

Differentiating between pneumonia and acute bronchitis is often difficult in primary care. There is no consensus regarding clinical decision rules for pneumonia, and guidelines differ between countries. Use of diagnostic tests and change of management over time is not known.

Aim

To calculate the proportion of diagnostic tests in the management of lower respiratory tract infections (LRTIs) in a low antibiotic prescribing country, and to evaluate if the use and prescription pattern has changed over time.

Design & setting

A register-based study on data from electronic health records from January 2006 to December 2014 in the Kronoberg county of south east Sweden.

Method

Data regarding use of C-reactive protein (CRP), chest x-rays (CXRs), microbiological tests, and antibiotic prescriptions were assessed for patients aged 18–79 years, with the diagnosis pneumonia, acute bronchitis, or cough.

Results

A total of 54 229 sickness episodes were analysed. Use of CRP increased during the study period from 61.3% to 77.5% for patients with pneumonia (P<0.001), and from 53.4% to 65.7% for patients with acute bronchitis (P<0.001). Use of CXR increased for patients with acute bronchitis from 3.1% to 5.1% (P<0.001). Use of microbiological tests increased for patients with pneumonia, from 1.8% to 5.1% (P<0.001). The antibiotic prescription rate decreased from 18.6 to 8.2 per 1000 inhabitants per year for patients with acute bronchitis, but did not change for patients with pneumonia.

Conclusion

Use of CRP and microbiological tests in the diagnostics of LRTIs increased despite the fact that the incidence of pneumonia and acute bronchitis was stable.

Accuracy of Biomarkers for the Diagnosis of Adult Community-acquired Pneumonia: A Meta-analysis

BACKGROUND

Biomarkers such as C-reactive protein (CRP) and procalcitonin may help distinguish community-acquired pneumonia (CAP) from other causes of lower respiratory tract infection.

METHODS

We performed a systematic review of the literature to identify prospective studies evaluating the accuracy of a biomarker in patients with acute cough or suspected CAP. We performed parallel abstraction of data regarding study inclusion, characteristics, quality, and test accuracy. Study quality was evaluated using QUADAS-2. Bivariate meta-analysis was performed using the mada package in R, and summary receiver operating characteristic (ROC) curves were created.

RESULTS

Fourteen studies met our inclusion and exclusion criteria; three were at low risk of bias and four at moderate risk of bias, largely due to failure to prespecify diagnostic thresholds. Considering all studies regardless of the cutoff used, CRP was most accurate (area under the ROC curve = 0.802), followed by leukocytosis (0.777) and procalcitonin (0.771). Lipopolysaccharide-binding protein and fibrinogen are promising, but were only studied in a single report. For CRP and procalcitonin, the positive and negative likelihood ratios (LR+ and LR-, respectively) varied inversely based on the cutoff. For CRP, LR+ and LR- were 2.08 and 0.32 for a cutoff of 20 mg/L, 3.64 and 0.36 for a cutoff of 50 mg/L, and 5.89 and 0.47 for a cutoff of 100 mg/L. For procalcitonin, LR+ and LR- were 2.50 and 0.39 for a cutoff of 0.10 µg/L, 5.43 and 0.62 for a cutoff of 0.25 µg/L, and 8.25 and 0.76 for a cutoff of 0.50 µg/L. The combination of CRP >49.5 mg/L and procalcitonin >0.1 µg/L had LR+ of 2.24 and LR- of 0.44.

CONCLUSIONS

The best evidence supports CRP as the preferred biomarker for diagnosis of outpatient CAP given its accuracy, low cost, and point-of-care availability.

Community-acquired pneumonia in primary care: clinical assessment and the usability of chest radiography

OBJECTIVES

To investigate the diagnostic value of different clinical and laboratory findings in pneumonia and to explore the association between the doctor's degree of suspicion and chest X-ray (CXR) result and to evaluate whether or not CXR should be used routinely in primary care, when available.

DESIGN

A three-year prospective study was conducted between September 2011 and December 2014.

SETTING

Two primary care settings in Linköping, Sweden.

SUBJECTS

A total of 103 adult patients with suspected pneumonia in primary care.

MAIN OUTCOME MEASURES

The physicians recorded results of a standardized medical physical examination, including laboratory results, and rated their suspicion into three degrees. The outcome of the diagnostic variables and the degree of suspicion was compared with the result of CXR.

RESULTS

Radiographic pneumonia was reported in 45% of patients. When the physicians were sure of the diagnosis radiographic pneumonia was found in 88% of cases (p < 0.001), when quite sure the frequency of positive CXR was 45%, and when not sure 28%. Elevated levels of C-reactive protein (CRP) ≥ 50mg/L were associated with the presence of radiographic pneumonia when the diagnosis was suspected (p < 0.001).

CONCLUSION

This study indicates that CXR can be useful if the physician is not sure of the diagnosis, but when sure one can rely on one's judgement without ordering CXR.

KEY POINTS

There are different guidelines but no consensus on how to manage community-acquired pneumonia in primary care. When the physician is sure of the diagnosis the judgement is reliable without chest X-ray and antibiotics can be safely prescribed. Chest X-ray can be useful in the assessment of pneumonia in primary care, when the physician is not sure of the diagnosis.

C-reactive protein and community-acquired pneumonia in ambulatory care: systematic review of diagnostic accuracy studies

BACKGROUND

There is uncertainty regarding the diagnostic value of C-reactive protein (CRP) in patients presenting with symptoms suggestive of community-acquired pneumonia (CAP) in community or ambulatory settings.

OBJECTIVE

We assessed the diagnostic value of CRP in primary care and accident and emergency departments in terms of ruling in or ruling out CAP.

METHODS

Diagnostic accuracy systematic review, we searched PubMed from January 1966 to September 2008 and EMBASE from January 1980 to September 2008 using a diagnostic accuracy search filter. We included cross-sectional or cohort studies that assess the diagnostic utility of CRP at different cut-points against a reference standard of chest X-ray. We calculated pooled positive and negative likelihood ratios (LRs) and assessed heterogeneity using the I(2) index.

RESULTS

Eight studies incorporating 2194 patients were included. The median prevalence of CAP was 14.6% (range 5%-89%). At a CRP cut-point of < or =20 mg/l, the pooled positive LR+ was 2.1 [95% confidence interval (CI) 1.8-2.4] and the pooled negative LR- was 0.33 (95% CI 0.25-0.43). At the two other CRP cut-points (< or =50, >100 mg/l), the results were heterogeneous, so the pooled results should be interpreted with caution.

CONCLUSIONS

CRP may be of value in ruling out a diagnosis of CAP in situations where the probability of CAP >10%, typically accident and emergency departments. In primary care, additional diagnostic testing with CRP is unlikely to alter the probability of CAP sufficiently to change subsequent management decisions such as antibiotic prescribing or referral to hospital.