Original Article
Clinical items not helpful in differentiating viral from bacterial lower respiratory tract infections in general practice

https://doi.org/10.1016/j.jclinepi.2004.08.004Get rights and content

Abstract

Objective

Incorrect and unnecessary antibiotic prescribing enhancing bacterial resistance rates might be reduced if viral and bacterial lower respiratory tract infections (LRTI) could be differentiated clinically. Whether this is possible is often doubted but has rarely been studied in general practice.

Study design and setting

This was an observational cohort study in 15 general practice surgeries in the Netherlands.

Results

Etiologic diagnoses were obtained in 112 of 234 patients with complete data (48%). Viral pathogens were found as often as bacterial pathogens. Haemophilus (para-) influenzae was most frequently found. None of the symptoms and signs correlated statistically significantly with viral or bacterial LRTI. Erythrocyte sedimentation rate >50 (odds ratio [OR] 2.3–3.3) and C-reactive protein (CRP) >20 (OR 2.1–4.6) were independent predictors for viral LRTI and bacterial LRTI when compared with microbiologically unexplained LRTI.

Conclusion

Extensive history-taking and physical examination did not provide items that predict viral or bacterial LRTI in adult patients in daily general practice. We could not confirm CRP to differentiate between viral and bacterial LRTI.

Introduction

Bacterial resistance rates are rising with increasing antibiotic consumption [1], [2], [3], [4], [5], [6], [7], [8]. The magnitude of the problem varies widely between countries [1]. Defensive prescription behavior, busy consultation hours, repeated incentives by the pharmaceutical industry, and reports of increasing occurrences of newly emerging pathogens are a constant threat to a rational or evidence-based approach (e.g., antibiotic prescribing in indicated cases only) by the physician toward a patient with a respiratory tract infection [4], [9], [10], [11], [12]. Furthermore, the physician's diagnostic uncertainty increases the likelihood of unnecessary antibiotic prescribing [13]. This is especially true in lower respiratory tract infections (LRTI), with a diagnosis in general practice of 30–55 new episodes per thousand patients per year [14], [15], [16], [17]; the infrequently occurring pneumonias (20% of all LRTI) are clinically misclassified in most cases [18], [19], [20]. Acute bronchitis almost exclusively accounts for the remainder (80%) of the LRTI cases. Antibiotics are prescribed in 80% of the cases [21], [22], [23] despite the fact that acute bronchitis is mostly self-limiting [24], [25] and often viral. In pneumonia it is considered to be malpractice to withhold antibiotic treatment from a patient.

General practitioners (GPs) can theoretically postpone the decision whether or not to prescribe antibiotics by taking sputum samples for microbiologic culture. However, the time delay before receiving the test result and (false-) negative test results in more than half of the samples [26], [27], [28] restrain the GP from more frequently submitting samples to the laboratories [29]. From a clinical point of view, GPs would be better off by having a viral instead of a bacteriologic diagnosis confirmed. This would enable them to select at least those patients who do not need antibiotics. However, waiting for seroconversion (approximately 4 weeks) before knowing whether or not the patient suffered from a viral infection is no option. As a result, the GP usually decides empirically, after history-taking and physical examination, whether or not to prescribe antibiotics to the patient. Correctly predicting specific pathogens on clinical grounds in pneumonia patients seems to be difficult in most cases [30], [31]. Moreover, the GPs' clinical assessment that an infection warranting antibiotics was present and bacterial infection being found were not related in a community-based study in the United Kingdom [32]. Diagnostic studies on clinical prediction of viral or bacterial LRTI in daily general practice could not be found. High C-reactive protein (CRP) values might be predictive for bacterial infections, although evidence is poor and conflicting [33], [34], [35], [36], [37], [38]. In summary, the diagnostic value of the clinical tools GPs have at their disposal to manage LRTI is largely unknown. The present study evaluated the predictive value of symptoms, signs, leukocyte count, erythrocyte sedimentation rate (ESR), and CRP for viral and bacterial LRTI, including pneumonia, in adult patients presenting with LRTI to a GP.

Section snippets

Patients and procedures

Adult patients presenting with the following symptoms and signs of LRTI to 25 GPs from 15 practices in the south of The Netherlands were eligible for the study: a new or increasing cough combined with at least one of the four respiratory criteria: dyspnoea, wheezing, chest pain, auscultation abnormalities; and at least one of the four general criteria: fever (≥38°C), perspiring, headache, myalgia. The GP had to be convinced of the diagnosis LRTI. Exclusion criteria were pregnancy and lactation,

Patients and etiologic diagnosis

Between January 1998 and April 1999, 247 LRTI patients 18–89 years of age (mean age 52) were included. One or more test results of 13 patients were missing: 11 blood samples for serologic analysis (first or second sample) and two sputum samples. An etiologic (microbiologic) diagnosis was obtained in 112 of the 234 remaining patients (48%) (Table 1). Viral LRTI (n = 49, 21%) was found as often as bacterial LRTI (n = 48, 21%). H. (para-) influenzae was the most common bacterial microorganism found

Discussion

The present diagnostic study on LRTI provides evidence of an assumption that is often prematurely derived from hospital studies and guidelines on pneumonia [12], [30], [33], [45], [46]: Extensive history-taking and physical examination do not provide clinical items that are useful to predict viral or bacterial etiology of LRTI in adult patients. Only in the theoretical situation of maximal contrast of the dependent variable in logistic regression analysis, proven viral versus proven bacterial

Acknowledgments

We thank the patients, general practitioners, and physicians' assistants who participated in this study. We thank Melanie Schnijderberg, Ruud Deurenberg, and Nancy London for their assistance with the logistics of the study.

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