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A 70-year-old woman is seen in an acute care clinic for fever, chills, shortness of breath, and a cough. She states that her son's family stayed with her over Thanksgiving weekend and they had a respiratory infection from which they recovered. She later contracted the respiratory illness also, but after two weeks her symptoms have worsened. A sputum Gram stain is shown below. Which of the following is the most likely cause of this patient's current symptoms?
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a. Haemophilus influenzae
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d. Respiratory syncytial virus
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e. Streptococcus pneumoniae
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The most correct answer is c, Staphylococcus aureus.
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The Gram stain shows large gram-positive cocci, predominantly in clumps, some with a grape-like appearance that is typical of Staphylococcus. Haemophilus is a gram-negative coccobacillus; Mycoplasma pneumoniae cannot be cultured on routine media; RSV does not take up Gram stain; and Streptococcus pneumoniae are typically gram-positive, lancet-shaped diplococci.
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A 55-year-old woman presents to the ER with new onset shortness of breath. Her chest x-ray shows a large right pleural effusion. A therapeutic thoracentesis is performed, and the fluid is sent to the laboratory. The pleural fluid/serum total protein ratio is 0.6 and the pleural fluid/serum LDH ratio is 0.7. Amylase and glucose levels are unremarkable on the pleural fluid. The culture and Gram stain are negative and the cytology results are negative for malignancy. Which of the following is most likely correct regarding the type and origin of her pleural fluid?
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a. The fluid is a transudate, and congestive heart failure should be excluded.
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b. The fluid is an exudate that is probably infected.
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c. The fluid is an exudate, and pulmonary embolism should be excluded.
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d. The fluid is a transudate, and nephrotic syndrome should be considered.
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e. The fluid is an exudate that could be of pancreatic origin.
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The most correct answer is c, an exudate and pulmonary embolism should be excluded.
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The pleural fluid/serum total [protein] ratio and the fluid/serum [LDH] ratio both indicate the fluid is an exudate. The culture and Gram stain are both negative, so infection is less likely. Amylase levels are unremarkable, as is cytology, so malignancy or pancreatic origin is unlikely. Excluding a pulmonary embolism is the best next diagnostic step among the choices offered.
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A 53-year-old man with chronic alcoholism and a history of squamous cell carcinoma of the esophagus has a pleural effusion. He has difficulty swallowing and left-sided chest pain on deep inspiration. A small amount of pleural fluid is obtained and the pleural fluid/serum protein ratio is 0.8. A specimen is sent to cytology, but it is Friday night and cytology results will not be ready until Monday. There is sufficient pleural fluid left to perform one more test. Which of the following would be most likely to establish the etiology of the pleural effusion in this patient?
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c. Pleural fluid/serum [LDH] ratio
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e. AFB (acid-fast bacillus) stain
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The most correct answer is b, requesting an amylase assay on the pleural effusion.
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The patient's history of squamous cell carcinoma of the esophagus, and the pleural fluid/serum [protein] ratio indicate an exudate, with malignancy high on the differential. While awaiting the cytology results, the test that would be most helpful in providing evidence for or against malignancy is for amylase activity, which would be elevated in malignant pleural effusions.