What is the role of pulmonary function testing in the diagnosis of Pneumocystis jiroveci pneumonia (PJP)?

Updated: Apr 24, 2019
  • Author: Shelley A Gilroy, MD, FACP, FIDSA; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Pulmonary function tests should be obtained as part of the initial noninvasive workup in patients with suspected P jiroveci pneumonia (PJP). Results may demonstrate a decreased diffusion capacity of carbon monoxide (DLCO) of less than 75% predicted. Decreased DLCO has a high sensitivity (89%-100%) but poor specificity (53%). PJP is unlikely if DLCO is normal.

When combined with normal or unchanged HRCT findings, pulmonary function tests may be used to identify patients unlikely to have PJP; such patients may be managed with observation alone.

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