Diagnosis of Legionella pneumonia based on Legionella urinary antigen testing of serum instead of urine in a hemodialysis patient

Abstract

A 71-year-old male, who had been receiving dialysis for 2 years, presented with a fever and precordial pain. He was diagnosed with left-sided pneumonia and was admitted to our hospital. He was assumed to have bacterial pneumonia and so was treated with ceftriaxone. The antibacterial therapy was not effective, and an inflammatory reaction and pulmonary infiltration developed. Legionella pneumonia was considered during the differential diagnosis of atypical pneumonia. As a Legionella urinary antigen test would have been difficult to perform as the patient was anuric, a serum sample was used instead of a urine sample for the test. The result was antigen-positive. Thereafter, the Legionella urinary antigen test was performed again using a small amount of urine (collected via a urethral catheter), and the result was also antigen-positive. The patient was finally diagnosed with Legionella pneumonia. He was administered levofloxacin, and he recovered immediately. It has been reported that hemodialysis patients are at risk of developing Legionella pneumonia, but it is often difficult to collect urine samples for examination from such patients. Legionella urinary antigen testing using serum samples instead of urine might be useful for diagnosing Legionella pneumonia among anuric dialysis patients.