A 32-year-old woman comes to the emergency department due to 7 days of fever and dry cough. She has also had progressive shortness of breath with minimal walking and climbing stairs. The patient was diagnosed with HIV infection a year ago and is not currently on antiretroviral treatment. She does not use tobacco, alcohol, or illicit drugs. Temperature is 38.4 C (101.1 F), blood pressure is 110/64 mm Hg, pulse is 106/min, and respiratory rate is 26/min. Pulse oxymetry is 87% on room air and decreases to 82% with minimal walking. Oropharyngeal thrush is present. Lung auscultation reveals scattered bilateral crackles and rhonchi. The abdomen is soft and nontender without organomegaly. No cyanosis, clubbing, or edema is present. Chest x-ray reveals diffuse interstitial opacities bilaterally. CD4 count is 85/mm³. The patient is admitted and started on empiric therapy. Twenty-four hours after admission, the induced sputum analysis is negative for Pneumocystis. On day 2 of hospitalization, the patient develops worsening dyspnea and hypoxia. Repeat chest x-ray reveals worsened interstitial infiltrate. Due to significant tachypnea and poor oxygenation, the patient is intubated. The patient is currently receiving trimethoprim-sulfamethoxazole, prednisone, ceftriaxone, and azithromycin. Blood cultures from admission are negative at 48 hours. Which of the following is the best next step in management of this patient?

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Explanation: 11ec2b69_bfb8_9c09_8f63_957bdf19419e_MD0005_00 This patient had respiratory decompensation on hospital day 2 after beginning empiric treatment for both Pneumocystis pneumonia (PCP) (trimethoprim-sulfamethoxazole, prednisone) and community-acquired pneumonia (ceftriaxone, azithromycin). PCP remains the most likely diagnosis in this patient with advanced HIV, indolent pulmonary symptoms, interstitial infiltrate, and respiratory decompensation following treatment (common even with concomitant corticosteroids). Given the critical nature of this patient's illness, a definitive diagnosis is now required. In patients with suspected PCP with negative induced sputum testing, the next diagnostic test of choice is a fiberscopic bronchoscopy with bronchoalveolar lavage. This test is highly sensitive (90%-100%) for diagnosis of PCP. Therefore, a negative result would make PCP extremely unlikely, suggesting the need to evaluate for other etiologies. A positive result would confirm the diagnosis in this critically ill patient. Bronchoalveolar lavage fluid could also be sent for studies evaluating for other respiratory pathogens or causes of respiratory decompensation. (Choice B) A definitive diagnosis is important due to the clinical severity of this case and the fact that up to 15% of patients with PCP have a concurrent pulmonary illness (eg, Mycobacterium tuberculosis). Clinical observation alone would not be prudent. (Choice C) High-resolution CT scan is likely to show evidence of PCP (eg, ground glass opacities) but is unlikely to provide a definitive diagnosis. PCP diagnosis requires the isolation of organisms in respiratory samples. (Choice D) Repeat blood cultures are not likely to provide a diagnosis as admission blood cultures are negative, PCP is the most likely diagnosis (AIDS, indolent pulmonary symptoms, interstitial infiltrate), and Pneumocystis jirovecii is not culturable. (Choice E) A transthoracic echocardiogram could help evaluate whether ventricular dysfunction was causing pulmonary edema with resultant respiratory decompensation and worsening pulmonary infiltrate. However, this patient had no evidence of volume overload (eg, edema) on admission and has several features (fever, immunocompromise) suggesting an infectious process. Infectious endocarditis with septic pulmonary emboli is also less likely in this patient with negative blood cultures and interstitial infiltrate. Educational objective: Patients with suspected Pneumocystis pneumonia require fiberscopic bronchoscopy with bronchoalveolar lavage if induced sputum samples do not yield a diagnosis.

A 32-Year-Old Woman Comes to the Emergency Department Due to 7