Lab diagnosis of infective endocarditis

Dr Dharmendra Sharma

Diagnosis of Infective Endocarditis is clinical

• Requires fulfillment of Duke’s criteria:

2 Major Criteria or

1 Major + 3 Minor or

5 Minor criteria

Duke’s criteria (Major)

1. Positive blood culture: – Growth of typical endocarditis causing bacteria in

two separate blood cultures.

– Persistently positive blood culture

– Single positive blood culture for Coxiella burnetii or positive serological detection of antibodies.

2. Evidence of endocardial involvement: – Positive echocardiogram

– Appearance of a new murmur

Duke’s criteria (Minor) 1. Predisposition: predisposing heart condition or injection

drug use 2. Fever ≥38.0°C (≥100.4°F) 3. Vascular phenomena:

– Arterial emboli – Splinter hemorrhages – Conjunctival hemorrhages – Janeway lesions

4. Immunologic phenomena: – Glomerulonephritis – Osler’s nodes – Roth’s spots – Rheumatoid factor

5. Microbiologic evidence: positive blood culture but not meeting major criterion as noted previously

Conjunctival Petechiae

Photo credit, Josh Fierer, M.D. medicine.ucsd.edu/clinicalimg/ Eye-Petechiae.html

Splinter Hemorrhages

1. Nonspecific

2. Nonblanching

3. Linear reddish-brown lesions found under the nail bed

4. Usually do NOT extend the entire length of the nail

Janeway Lesions

1. Erythematous, blanching macules

2. Non painful

3. Located on palms and soles

Roth’s spots

Blood culture

• Minimum of three blood cultures

• Three separate venipuncture sites

• Obtain 7-10 mL in adults and 3-5mL in children