RHEUMATIC FEVER[ LABORATORY MANIFESTATIONS

]SITI MARIAM BINTI MOHD HAMZAH

Minor criteria:Clinical & Laboratory features ELEVATED ACUTE PHASE REACTANTS:

ERYTHROCYTE SEDIMENTATION RATE

C-REACTIVE PROTEIN PROLONGED P-R INTERVAL

ESSENTIAL CRITERIA this refers to supporting evidence of antecedent streptococcal

infection, NOT for diagnosing ARF

• Positive throat culture for streptococci

• Streptococcal serum antibody tests

• Presence of residua of scarlet fever

ACUTE PHASE IN RHEUMATIC FEVER Acute phase develop in a small proportion of individuals several

weeks after a streptococcal infection of the throat. ACUTE PHASE RESPONSE is a major pathophysiological

phenomenon which accompanies inflammation resulting from tissue damage. (etiopathogenesis)

ACUTE PHASE REACTANTS get altered both in acute and chronic inflammation.

Streptococcal proteins display molecular mimicry recognized by the immune system; bacterial M-proteins & human cardiac antigens

T-cells that are responsive to streptococcal M-protein infiltrate the valve through valvular endothelium, activated by the binding antistreptococcal carbohydrates with release of TNF and IL

INFL

AMM

ATIO N

1.LABORATORY

FEATURES

ELEVATED ERYTHROCYTE SEDIMENTATION RATE (ESR)

• Normal value• 10 mm/hour in men• 20 mm/hour in women

• In rheumatic fever,• At least 60 mm/hour in low-

risk populations• At least 30 mm/hour in high-

risk populations

• Rise in ESR suggests inflammatory processes. In many cases, the level of

ESR may reflect the severity of the

inflammatory process.

ELEVATED C-REACTIVE PROTEIN (CRP)

• CRP is a beta-globulin present in serum, capable of reacting with the outer coat of pneumococci.

• Normally it is absent from human plasma. When inflammatory processes occur, the liver produces an identical protein which can be detected by a slide test using readymade reagents.

• CRP level in rheumatic fever, is at least 3.0 mg/dl

PROLONGED P-R INTERVAL• P-R interval is a measure of the atrioventricular

(AV) conduction. Prolonged PR interval indicates AV block.

• Normal PR interval is 0.12 to 0.20 sec, slightly shorter in children with upper limit being 0.18 sec.

• In case of rheumatic fever, it is due to the inflammation of the myocardium that caused delay in the AV conduction, thus prolonged PR interval.

2.ESSENTIAL CRITERIA

POSITIVE THROAT CULTURE FOR STREPTOCOCCI

The gold standard for detecting Streptococcus pyogenes remains a throat swab cultured on blood agar.

If possible, throat swabs should be examined for all patients with clinically suspected streptococcal upper respiratory tract infection.

STREPTOCOCCAL SERUM ANTIBODY TESTSThe most commonly performed and commercially

available tests are the antistreptolysin-O test, and the antideoxyribonuclease-B test.

At least one anti-streptococcal antibody titre should be elevated for a diagnosis of acute RF.

Although a single elevated antibody titre may be useful for documenting a previous streptococcal infection, it is recommended that an additional test be performed 3–4 weeks after the onset of RF. Rising titer of antibody is a stronger evidence for a recent streptococcal infection.

http://www.who.int/cardiovascular_diseases/resources/en/cvd_trs923.pdf

A serum antibody is judged to be elevated if the titre exceeds the upper limit of the normal titre range

PRESENCE OF RESIDUA OF SCARLET FEVER

The desquamation of skin of palms and soles indicates that the patient has had scarlet fever within the previous 2 weeks. Scarlet fever is rare in India.

an infectious bacterial disease affecting especially children, and causing fever

and a scarlet rash. It is caused by streptococci.

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