A 73-year-old woman comes to the emergency department with a 3-day history of worsening breathlessness and cough productive of thick, rust-colored sputum. The patient has a longstanding history of hypertension. Temperature is 38.3 C (101 F), blood pressure is 130/68 mm Hg, pulse is 102/min, and respirations are 24/min. BMI is 27 kg/m². Jugular venous pressure is normal and there is no lower extremity edema. Heart sounds are normal with no murmur. Lung auscultation reveals left lower lobe crackles and bronchial breath sounds. Leukocyte count is 14,000/mm³ with 80% neutrophils and 7% bands, hemoglobin is 13.6 g/dL, and platelets are 400,000/mm³. Serum levels of which of the following are most likely to be elevated in this patient?

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Acute phase reactants (APRs) are proteins whose serum concentrations change by ≥25% during periods of inflammation. Several APRs have diagnostic and prognostic utility and can be interpreted on the basis of serum concentrations: Positive APRs (serum levels rise in acute inflammatory states) include fibrinogen, C-reactive protein, ferritin, hepcidin, ceruloplasmin, haptoglobin, von Willebrand factor, and complement. The erythrocyte sedimentation rate (the time required for erythrocytes to settle from suspension) is an indirect measure of positive APRs. Negative APRs (serum levels fall in acute inflammatory states) include albumin, transferrin, and transthyretin (prealbumin). Procalcitonin, a precursor of calcitonin produced by monocytes and the C cells of the thyroid, is a unique APR that has positive and negative properties. Levels rise in response to bacterial toxins and fall in response to viral infections, and therefore levels can suggest the etiology of community-acquired pneumonia. This patient has lobar pneumonia manifesting with fever, rust-colored sputum, and neutrophil-predominant leukocytosis, likely due to a bacterial infection (eg, Streptococcus pneumoniae). Therefore, procalcitonin levels are expected to be elevated. (Choice A) B-type natriuretic peptide is secreted by the ventricles in response to elevated ventricular filling pressure, which is seen in decompensated heart failure. Patients with heart failure often have elevated jugular venous pressure and lower extremity edema, pulmonary examination findings are usually bilateral, and fevers and leukocytosis would not be expected. (Choice B) Cold agglutinins (ie, IgM against erythrocyte I antigen) are nonspecific but often seen in patients with Mycoplasma pneumoniae. However, patients with M pneumoniae typically present with a dry cough and pharyngitis, and laboratory results demonstrate a mild hemolytic anemia with a normal leukocyte count. When pneumonia occurs due to M pneumoniae, examination findings are characteristically scattered and bilateral. (Choices C and E) Prealbumin (transthyretin) and transferrin are negative APRs and would be decreased in this acutely ill patient. Prealbumin levels are also decreased in cases of malnutrition and may be helpful in evaluation of nutritional status. Transferrin is also used to determine iron status. Educational objective: Acute phase reactants (APRs) are proteins whose serum concentrations change by ≥25% during periods of inflammation. Procalcitonin is a unique APR that can rise or fall depending on the etiology of the infection; elevated levels correlate with a bacterial source, whereas low levels indicate a viral source. __________ References: Role of procalcitonin in guiding antibiotic therapy. (http://www.ncbi.nlm.nih.gov/pubmed/23172263)

A 73-Year-Old Woman Comes to the Emergency Department with a 3-Day