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Published on: April 2, 2013
Early clinical differentiation between Legionnaires' disease and other sporadic pneumonias
Abstract:
Early diagnosis of Legionnaires' disease is difficult because other pathogens cause a similar clinical picture and microbiologic tests are usually only of retrospective value. Since May 1977, 17 patients with sporadic cases of Legionnaires' disease have been admitted, all previously well, the diagnosis being made with standard serologic or bacteriologic criteria. From the clinical, laboratory, and radiologic findings, we propose criteria that may enable the clinician to make a diagnosis earlier in many cases, differentiating them from other pneumonias. Within 24 hours of admission, any three of the following four features are strongly suggestive of Legionnaires' disease: [1] prodromal "viral" illness, [2] dry cough or confusion or diarrhoea, [3] lymphopenia without marked neutrophilia, [4] hyponatremia. Two thirds of cases had at least three of these features, and no false-positive diagnoses would have been made in other pneumonias that were serologically negative for Legionnaires' disease if these proposed criteria had been applied diagnostically. In the next few days the diagnosis is very likely if microbiologic tests are negative and if there is radiologic extension, abnormal liver function test results, or hypoalbuminemia.
Insights
Early diagnosis of Legionnaires' disease is challenging. New criteria including viral illness, dry cough, confusion, diarrhea, lymphopenia, and hyponatremia can aid earlier identification of Legionnaires' disease.
Area of Science:
- Infectious Diseases
- Clinical Microbiology
- Pulmonary Medicine
Background:
- Legionnaires' disease diagnosis is often delayed due to overlapping symptoms with other pneumonias.
- Current diagnostic methods, including serologic and bacteriologic tests, typically provide retrospective confirmation.
Purpose of the Study:
- To establish early clinical criteria for diagnosing Legionnaires' disease.
- To differentiate Legionnaires' disease from other pneumonias for timely intervention.
Main Methods:
- Analysis of clinical, laboratory, and radiologic findings from 17 sporadic cases of Legionnaires' disease.
- Development and evaluation of proposed diagnostic criteria based on early presenting features.
Main Results:
- Within 24 hours of admission, three of four features strongly suggest Legionnaires' disease: prodromal viral illness, dry cough/confusion/diarrhea, lymphopenia without neutrophilia, and hyponatremia.
- Two-thirds of patients exhibited at least three of these features.
- Applying these criteria could prevent false-positive diagnoses in serologically negative pneumonia cases.
Conclusions:
- Proposed clinical criteria can facilitate earlier diagnosis of Legionnaires' disease.
- Further supportive indicators include negative microbiologic tests, radiologic extension, abnormal liver function, and hypoalbuminemia in the subsequent days.
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