Rheumatic fever laboratory tests
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Varun Kumar, M.B.B.S. Anthony Gallo, B.S. [2]
Overview
Laboratory findings consistent with the diagnosis of rheumatic fever include elevated inflammatory markers, presence of streptococcal infection, and elevated or rising antistreptolysin O antibody titer.
Inflammatory Markers
The following inflammatory markers are often elevated:
- Leukocytes
- C-reactive protein
- Erythrocyte sedimentation rate (ESR)
Laboratory Findings
Throat Culture
Throat culture for group A beta-hemolytic streptococci may be performed. However many patients may have negative culture by the time rheumatic fever develops[1].
Rapid Streptococcal Antigen
Rapid streptococcal antigen test may be performed. However, it has a lower sensitivity (70%) and statistically equal specificity (98%) as throat culture; a negative test results rules out streptococcal infection.[2]
Antistreptolysin O Antibody
Elevated or rising antistreptolysin O antibody titer is often noted. The antibodies usually peak approximately during fourth or fifth week after the onset of infection. Patients should be tested at intervals of two weeks to detect raising titers. Antistreptococcal antibodies may also be noted in patients who are streptococcal carriers with asymptomatic pharyngitis.
Leukocytosis
A marked leukocytosis is present.
C-Reactive Protein
An elevated C-reactive protein level is present.
Erythrocyte Sedimentation Rate
An elevated erythrocyte sedimentation rate is present.
Biopsy of Endocardium
Though endomyocardial biopsy may help in confirming the presence of carditis, it is not recommended as a routine diagnostic and prognostic tool.[3]
References
- ↑ "Guidelines for the diagnosis of rheumatic fever. Jones Criteria, 1992 update. Special Writing Group of the Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease of the Council on Cardiovascular Disease in the Young of the American Heart Association". JAMA. 268 (15): 2069–73. 1992. PMID 1404745.
- ↑ Choby BA (2009). "Diagnosis and treatment of streptococcal pharyngitis". Am Fam Physician. 79 (5): 383–90. PMID 19275067.
- ↑ Narula J, Chopra P, Talwar KK, Reddy KS, Vasan RS, Tandon R; et al. (1993). "Does endomyocardial biopsy aid in the diagnosis of active rheumatic carditis?". Circulation. 88 (5 Pt 1): 2198–205. PMID 8222115.