Rheumatic Fever in Emergency Medicine Workup

Updated: Jul 19, 2021
  • Author: Steven J Parrillo, DO, FACOEP, FACEP; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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Laboratory Studies

The diagnosis of group A strep pharyngitis can be confirmed with a rapid antigen detection test or a throat culture, with throat culture considered the gold standard. Note that the Center for Disease Control and Prevention (CDC) advises that testing for group A beta-hemolytic Streptococcus (GABHS) pharyngitis is not routinely indicated for children younger than 3 years of age or for adults, since acute rheumatic fever (ARF) is very rare in those age groups. In children older than 3 years of age, the CDC recommends confirming the diagnosis of GABHS pharyngitis, which can be done with a positive rapid test. In a child with a negative rapid test, however, a follow-up throat culture should be performed. [1]

Similarly, the Infectious Disease Society of America and the American Heart Association recommend that the diagnosis of GABHS infection be confirmed. In children and adolescents, a negative rapid antigen test result should be followed by culture unless the physician has determined that in his or her own practice the rapid antigen test is comparable to a throat culture. [30] However, a culture positive for GABHS does not definitively prove active infection; some patients are carriers.

No specific confirmatory laboratory tests exist for acute rheumatic fever. However, several laboratory findings indicate continuing rheumatic inflammation. Some are part of the Jones minor criteria. Streptococcal antibody tests disclose preceding but not current streptococcal infection.

Acute-phase reactants (eg, erythrocyte sedimentation rate [ESR], C-reactive protein [CRP]) may show an increase, as may serum complement, mucoproteins, alpha-2, and gamma globulins. Anemia is usually caused by suppression of erythropoiesis.

PR-interval prolongation is present in approximately 25% of all cases and is neither specific for nor diagnostic of acute rheumatic fever.

Although there are a few small studies that show the contrary, troponins have not been shown to be helpful in making the diagnosis because ischemia and necrosis are not the major cardiac problems. [16]

In patients with arthritis, synovial fluid analysis may demonstrate an elevated white blood cell count with no crystals or organisms.

Differences exist among nations in terms of diagnosing and treating GABHS pharyngitis. Most North American, French, and Finnish guidelines consider diagnosis of streptococcal infection essential (with either rapid antigen detection or with formal culture) and advise antibiotic therapy when streptococci is detected. Several European guidelines consider streptococcal infection a self-limited disease and do not recommend antibiotics.


Imaging Studies

Echocardiography may be helpful in establishing carditis. Some suggest it be performed in all suspected cases. [15]

Chest radiography should be performed to determine the presence of cardiomegaly and congestive heart failure.