X-Rays Unreliable for Diagnosing Pneumonia in HD Patients

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NATIONAL HARBOR, Md.—Chest X-rays are unreliable for diagnosing pneumonia in hemodialysis (HD) patients, researchers reported at the National Kidney Foundation 2012 Spring Clinical Meetings.

Pneumonia and pulmonary edema commonly occur among HD patients. Chest X-rays are used routinely in clinical practice to assist with the differential diagnosis, but their reliability has not been evaluated in this patient population, the researchers explained.

Nephrology fellow Eric K. Judd, MD, and colleagues at the University of Alabama at Birmingham identified 122 HD patients admitted with a diagnosis of pneumonia from the emergency department of a large university hospital during a one-year period. The investigators excluded 54 subjects because of missing dialysis records and other reasons, leaving 68 patients in the study. Two experienced radiologists blinded to patients' clinical course and subsequent imaging studies independently interpreted the admission chest X-rays for the presence of pneumonia or pulmonary edema. Two internal-medicine trained physicians independently determined the presence of pneumonia and pulmonary edema after reviewing patients' entire hospitalization records. Dr. Judd's group assessed the level of agreement among the observers.

The radiologists agreed on the diagnosis of pneumonia and pulmonary edema in 58.8% and 55.9% of cases, respectively, whereas the clinicians agreed in 60.3% and 76.5% of cases, respectively.
Dr. Judd reported that a chest X-ray has a 50% sensitivity for diagnosing pneumonia in an HD patient and a positive predictive value of 25%.

The investigators concluded that there is substantial disagreement between experienced radiologists on the radiologic diagnosis of pneumonia and pulmonary edema in HD patients, perhaps reflecting uncertainty about the etiology of the pulmonary infiltrate in this population. Clinicians more frequently agreed on the diagnosis of pulmonary edema than of pneumonia, suggesting that pneumonia is more difficult to diagnose clinically. 

Admission chest X-rays are not an accurate or reliable test for diagnosing pneumonia in HD patients, Dr. Judd noted.
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