Criteria for each item in the six-point scoring system.
Legionella pneumophila is one of the important pathogens in community-acquired (CAP) and hospital-acquired pneumonia that can cause severe pneumonia. Early diagnosis and treatment of Legionella pneumonia (LP) are essential because inappropriate therapy for Legionella pneumonia has been reported to worsen the prognosis. The most frequently identified causative pathogen of Legionella pneumonia is Legionella pneumophila serogroup 1. Legionella pneumonia due to non-Legionella pneumophila serogroup 1 is seen in 20% of cases. In diagnosing Legionella pneumonia caused by non-Legionella pneumophila serogroup 1, the urinary antigen test is usually negative; therefore, we need to suspect Legionella pneumonia by clinical information such as symptoms, vital signs, laboratory findings, and radiological findings. Based on our previous report, Legionella pneumonia due to non-Legionella pneumophila serogroup 1 was a mild to severe pneumonia. In addition, in about half of the patients, we could not suspect Legionella pneumonia using a six-point scoring system, which is one of the diagnostic scoring systems. Recently, a new urinary antigen test kit that could theoretically diagnose Legionella pneumonia due to non-Legionella pneumophila serogroup 1 was released in Japan. This can help in early diagnosis of Legionella pneumonia, including the one caused by non-Legionella pneumophila serogroup 1.
- Legionella pneumonia
- Legionella pneumophila serogroup 1
- non-Legionella pneumophila serogroup 1
- urinary antigen
The most frequently identified causative microorganism of
The gold standard in the diagnosis of LP is the identification of
Currently, a urinary antigen test that detects soluble antigens is widely used for diagnosing LP in daily clinical practice worldwide. This diagnostic method is very useful because the examination procedure is simple and the results are known quickly. In a systematic review and meta-analysis, Shimada et al. reported that the specificity of the
The diagnostic key for LP due to non-
Legionellapneumonia due to non- Legionella pneumophilaserogroup 1
2.1 Previous reports
In earlier studies, LP due to non-
There have been many case reports of LP caused by non-
2.2 Diagnostic scoring system
We cannot rule out LP by a negative result of the urinary antigen test because the sensitivity of this test is not very good. To diagnose LP with a negative urinary antigen test, we need to suspect it based on the symptoms, vital signs, laboratory examinations, and radiological findings.
In 1998, Cunha advocated a diagnostic scoring system for LP called the “Winthrop-University Hospital (WUH) criteria” . The WUH criteria comprised 15 clinical findings and seven laboratory findings, and it was therefore thought to be too complicated to use in the daily clinical practice.
In 2009, Fiumefreddo proposed a six-point scoring system for predicting LP , and this scoring system was validated by Haubitz . This scoring system comprised one symptom, one vital sign, and four laboratory findings. The criteria for the six items are listed in Table 1. A score ≥5 had very high specificity (99.0%) and a high positive predictive value (17.4%), whereas a score <2 had high sensitivity (94.4%) and a high negative predictive value (99.6%). In our previous reports , using a cutoff value of ≥2 points, the sensitivity of this scoring system was 54.5% for non-
|C-reactive protein||>187 mg/L|
|Lactate dehydrogenase||>225 mmol/L|
|Platelets||<171 × 109/L|
|Serum sodium||<133 mmol/L|
3. Future perspective
Patients with LP have a worse prognosis if they are not treated with appropriate antibiotic therapy as soon as possible. Some patients with LP due to
In February 2019, Asahi Kasei Pharma Corporation released a urinary antigen test kit that could diagnose LP due to non-
In the future, we expect that early diagnosis of LP including non-
LP due to non-
The authors would like to thank all of our colleagues who recruited and treated the patients. They would also like to thank Hiroyuki Fujii from the Department of Clinical Laboratory, Ohara Healthcare Foundation, Kurashiki Central Hospital, for performing sputum culture for
Conflict of interest
The authors declare no conflict of interest.