eMedicine Specialties > Infectious Diseases > Lower Respiratory Tract Infections

Nursing Home Acquired Pneumonia: Differential Diagnoses & Workup

Author: Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Contributor Information and Disclosures

Updated: Jun 27, 2008

Differential Diagnoses

Pleural Effusion
Pulmonary Embolism

Other Problems to Be Considered

Most patients from chronic care facilities who are transferred to acute care hospitals do not have nursing home–acquired pneumonia (NHAP). The most common causes of diagnostic confusion in patients with NHAP are noninfectious cardiac and pulmonary disorders.

CHF is the most common disorder that resembles NHAP in the chronic care facility setting. CHF may represent an exacerbation of preexisting CHF, resulting in increasing shortness of breath for the patient, which mimics the presentation of NHAP.

The clinical presentation of patients in nursing homes who develop asymptomatic acute myocardial infarctions may also mimic the clinical presentation of patients with NHAP. Myocardial infarction may be associated with fever, shortness of breath, and chest pain; all are signs that mimic NHAP.

Many elderly patients are unable to raise sputum, making the absence of a productive cough an inadequate determination to differentiate NHAP and CHF.

Preexisting lung disease, pulmonary emboli, and bronchogenic malignancies mimic NHAP. Collagen vascular diseases affecting the lungs, pulmonary drug reactions, and pulmonary hemorrhage may also mimic NHAP.

Chest radiography is the best study for diagnosing NHAP. Patients with NHAP have a segmental or lobar distribution of infiltrates, as seen on chest radiographs. Patients with CHF have a redistribution of vasculature to the upper lobes, usually accompanied by cardiomegaly. Verify cardiomegaly by physical examination. If CHF is present, it usually is accompanied by an S3 gallop rhythm.

Preexisting chest radiographs may reveal previous interstitial lung disease that may mimic the appearance of NHAP. Chest radiography is the primary tool for ruling out the mimics of pneumonia and any new or preexisting lung disorders.

Fever that is equal to or greater than 102°F and accompanied by pulmonary symptoms suggests NHAP, especially when accompanied by a productive cough. However, in elderly patients who are the usual residents of chronic care facilities, the febrile response may be blunted. Therefore, the absence of fever or the presence of a low-grade fever is unhelpful in differentiating NHAP from its mimics.

Pleural effusions occasionally cause diagnostic confusion in the diagnosis of pneumonia. Bacterial pneumonias, particularly infections with S pneumoniae and H influenzae, may be accompanied by pleural effusion. However, pleural effusions without associated infiltrates are not pneumonia. Bilateral pleural effusion rarely, if ever, results from an infectious etiology. The presence of bilateral pleural effusions with unilateral or bilateral pulmonary infiltrates suggests a noninfectious etiology, and the workup should be designed accordingly.

Workup

Laboratory Studies

  • Blood cultures
    • Obtain blood cultures from all patients with community-acquired pneumonia (CAP) and nursing home–acquired pneumonia (NHAP).
    • Blood culture findings are usually positive if infection with S pneumoniae or H influenzae is causing the patient's pneumonia.
    • The yield of positive blood cultures in NHAP is lower than in CAP, which may represent a difference in the time each culture was taken. Patients with CAP who are admitted to an acute care facility usually have blood cultures drawn in the emergency room or soon after admission. Patients who are transferred to an acute care hospital from a chronic care facility may not have blood cultures drawn for many hours or days after the onset of pneumonia. These factors may account for the difference in culture yields.
  • CBC count
    • Physicians usually obtain blood counts, but these tests are not helpful, because the results are nonspecific.
    • Leukocytosis with a left shift is due to stress to the individual, which may occur with NHAP, an acute myocardial infarction, pulmonary emboli, dehydration, or any cause of stress. Therefore, the clinician should not assume that leukocytosis with a left shift is diagnostic of NHAP.
    • The diagnosis of NHAP rests on excluding the mimics of pneumonia and on the presence of characteristic findings on chest radiographs.
  • Sputum staining and culture
    • Stain sputum using a Gram stain and perform culture studies from patients with a productive cough who do not have chronic bronchitis.
    • Physicians cannot interpret sputum culture results from patients with chronic bronchitis because the results usually show normal flora or mixed flora, which is unhelpful to the clinician.
    • For sputum specimens to be useful in determining the etiology of the pneumonia, they must be of good quality and must reflect the lower respiratory tract flora. A poor specimen collection, as evidenced by the presence of epithelial squamous cell contamination and a relative lack of polymorphonuclear neutrophils or multiple organisms, suggests that the specimen is invalid and unreliable.
  • Multiple pathogens are not a feature of NHAP. Dual infections are rare in both NHAP and CAP.
  • Aspiration pneumonia due to anaerobic pharyngeal flora is the only polymicrobial respiratory tract infection that is considered community- or nursing home–acquired. The presence of a single causative pathogen generally excludes anaerobic aspiration pneumonia in patients with CAP or NHAP.

Imaging Studies

  • Chest radiography is the primary tool to differentiate the mimics of pneumonia from NHAP. If the resolution of the chest radiograph is insufficient to differentiate NHAP, consider obtaining a chest CT scan.

Other Tests

  • Obtain an ECG and cardiac enzymes in patients who may have a cardiac explanation for their pulmonary symptoms, as evidenced by their history, physical, or chest radiograph findings. ECG and cardiac enzymes are helpful in ruling out silent myocardial infarctions, which are not uncommon in elderly patients.
  • Bacterial blood gases or lung scans may be useful in ruling out pulmonary emboli as a cause of the patient's pulmonary symptoms.
  • If considering Legionnaires disease, a rare cause of sporadic pneumonia in chronic care facilities, obtain liver function tests.
  • Patients presenting with extrapulmonary findings in a chronic care facility may have NHAP caused by C pneumoniae infection. In such patients, C pneumoniae immunoglobulin (Ig) M and IgG titers may be diagnostic. IgA may also help to clarify if a patient is experiencing a relapse or a reinfection with Chlamydia. C pneumoniae infection usually occurs as part of an outbreak and should be readily recognizable in the nursing home setting because the infection occurs in clusters and is characterized by extrapulmonary features that set it apart from the usual bacterial causes of NHAP.

Procedures

  • Patients with pleural effusions unrelated to a nephrotic syndrome, uremia, hypoalbuminemia, cirrhosis, or heart failure require diagnostic thoracentesis. Physicians should test the thoracentesis fluid using Gram stain and culture studies as well as pH, glucose, protein, cell count, and differential. This procedure may reveal the causal pathogen if blood culture results are negative and if sputum is not available.

Histologic Findings

Findings include local polymorphonuclear neutrophil infiltration of infected lung areas without cavitation, necrosis, or blood vessel invasion.

More on Nursing Home Acquired Pneumonia

Overview: Nursing Home Acquired Pneumonia
Differential Diagnoses & Workup: Nursing Home Acquired Pneumonia
Treatment & Medication: Nursing Home Acquired Pneumonia
Follow-up: Nursing Home Acquired Pneumonia
References
Further Reading
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Further Reading

For additional information, see Medscape's Pneumonia Resource Center.

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Keywords

nursing home–acquired pneumonia, NHAP, pneumonia in chronic care facilities, Streptococcus pneumoniae, S pneumoniae, Haemophilus influenzae, H influenzae, Moraxella catarrhalis, M catarrhalis, Legionella, Chlamydia pneumoniae, C pneumoniae, aspiration pneumonia, chronic bronchitis, CNS disease, esophageal disease, decreased gag reflex, community-acquired pneumonia, CAP, nosocomial pneumonia, NP

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Contributor Information and Disclosures

Author

Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Medical Editor

Wesley W Emmons, MD, FACP, Assistant Professor, Department of Medicine, Thomas Jefferson University; Consulting Staff, Infectious Diseases Section, Department of Internal Medicine, Christiana Care, Newark, DE
Wesley W Emmons, MD, FACP is a member of the following medical societies: American College of Physicians, American Medical Association, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, and International AIDS Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Ronald A Greenfield, MD, Professor, Department of Internal Medicine, Section of Infectious Diseases, University of Oklahoma College of Medicine
Ronald A Greenfield, MD is a member of the following medical societies: American College of Physicians, American Federation for Medical Research, American Society for Microbiology, Central Society for Clinical Research, Infectious Diseases Society of America, Medical Mycology Society of the Americas, Phi Beta Kappa, Southern Society for Clinical Investigation, and Southwestern Association of Clinical Microbiology
Disclosure: Pfizer Honoraria Speaking and teaching; Gilead Honoraria Speaking and teaching; Ortho McNeil Honoraria Speaking and teaching; Wyeth Honoraria Speaking and teaching; Abbott Honoraria Speaking and teaching; Astellas Honoraria Speaking and teaching; Cubist  Speaking and teaching

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Michael Stuart Bronze, MD, Professor, Stewart G Wolf Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center
Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physician Executives, American College of Physicians, American College of Physicians-American Society of Internal Medicine, American Federation for Clinical Research, American Medical Association, American Society for Microbiology, Association of Professors of Medicine, Association of Program Directors in Internal Medicine, Infectious Diseases Society of America, Oklahoma State Medical Association, and Southern Society for Clinical Investigation
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