Following Current Legionella Testing Recommendations Results in Missed Cases

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.