Critical Care Medicine-Pulmonary Disorders>>>>>Pulmonary Infections
Question 6#

A 38-year-old man with human immunodeficiency virus (HIV) and a CD4+ count of 100 cells/µL is admitted to the ICU with respiratory failure from the medical ward. He reports 1 week of progressive dyspnea on exertion and chills. He had been treated with vancomycin and meropenem since his arrival to the ED 1 day ago. He is intubated and mechanically ventilated on volume controlassist control, tidal volume 6 mL/kg ideal body weight, respiratory rate 18/min, FiO2 0.7, and PEEP 8 cm H2O. His initial vital signs are:

Initial laboratory data are remarkable for a (1,3)-beta-d-glucan >200 pg/mL and LDH 100 U/L. On day 1 of his ICU stay, a bronchoscopy with bronchoalveolar lavage is performed and the Pneumocystis examination is negative.

Which of the following can result in an elevated 1-3 beta-d-glucan blood test in this patient?

A. Treatment with meropenem
B. Cryptococcus neoformans
C. Blastomyces dermatitidis
D. Treatment with vancomycin
E. Mucormycosis

Correct Answer is A

Comment:

Correct Answer: A

The (1,3)-beta-d-glucan test is a common, commercially available assay that detects a polysaccharide element of fungal cell walls that is found in most fungi. Notable exceptions to this are cryptococci, zygomycetes (eg mucormycoses), and Blastomyces dermatitidis, which either completely lack this element or produce it at minimal levels (answer B, answer C, and answer E are incorrect). This test, therefore, cannot be used to rule out infection with these fungal organisms. Notably, beta-lactam antibiotics may react with this assay and produce false-positive results (answer A is correct; answer D is incorrect). The (1,3)-beta-d-glucan has been studied as a noninvasive diagnostic test for pneumocystis pneumonia and has good sensitivity in patients with HIV. However, bronchoalveolar lavage remains the gold standard of the diagnosis of pneumocystis pneumonia.

Reference:

  1. Karageorgopoulos DE, Qu JM, Korbila IP, Zhu YG, Vasileiou VA, Falagas ME. Accuracy of β-D-glucan for the diagnosis of Pneumocystis jirovecii pneumonia: a meta-analysis. Clin Microbiol Infect. 2013;19(1):39-49.