Following Current Legionella Testing Recommendations Results in Missed Cases

September 8, 2011

It is unclear how often patients with pneumonia are assessed for Legionella in endemic areas. Additionally, the sensitivity of the IDSA/ATS criteria for recommended Legionella testing is undefined. Investigators Brian Hollenbeck, Irene Dupont and Leonard Mermel performed a single-center, retrospective study of patients diagnosed with Legionella pneumonia at Rhode Island Hospital to determine: 1) how often Legionella diagnostic testing is obtained on patients with pneumonia at the time of hospitalization or when pneumonia developed during hospitalization; and 2) how often patients with Legionella pneumonia met at least one of the five criteria in the IDSA/ATS guidelines recommending a work-up for Legionella. Patients with Legionella pneumonia were identified using an infection control software program. Medical records of these patients were then reviewed.

Thirty-five percent of patients with a discharge diagnosis of pneumonia had Legionella urine antigen testing and/or a Legionella culture performed. Forty-four percent of patients who had a bronchoscopic specimen sent for microbiologic testing had a Legionella culture performed on the bronchoscopic specimen and/or Legionella urine antigen testing. Of 37 adult patients with Legionella pneumonia, 22 (59 percent) met the IDSA-ATS criteria recommending Legionella testing.

The researchers report that following current recommendations for Legionella testing missed 41 percent of Legionella cases in adults in our single-center study. A work-up for Legionella (i.e., urine antigen test and/or culture) was performed in less than half of patients who have a bronchoscopic specimen sent for microbiologic testing. Their work was published in BMC Infectious Diseases.

Reference: Hollenbeck B, Dupont I and Mermel LA. How often is a work-up for Legionella pursued in patients with pneumonia? A retrospective study. BMC Infectious Diseases 2011, 11:237doi:10.1186/1471-2334-11-237.