Acute phase reactants

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What is ESR?
Erythrocyte sedimentation rate
Old, well-established acute phase reactant
Measures the distance that erythrocytes have fallen after one hour in a vertical column of anticoagulated blood (measured in mm/hr)
Primarily affected by fibrinogen
What is CRP?
C-reactive protein
Acute phase protein synthesized by the liver
Part of the innate immune system
5 positive acute phase reactants (apart from CRP and ESR)
Ferritin
Procalcitonin (specific for infection)
Fibrinogen
Alpha-1 antitrypsin
Haptoglobin
3 negative acute phase reactants
Albumin
Transferrin
Transthyretin
What are the advantages of ESR?
Better established
Cheaper (therefore more widely available)
What are the advantages of CRP?
More sensitive
More specific
More responsive to changes in inflammatory state
What are 2 conditions that elevate ESR in the absence of an inflammatory state?
Anaemia
Macrocytosis
What are 2 conditions that depress ESR?
Polycythaemia rubra vera
Leukocytosis
What are the 4 conditions that must be considered in a patient with an extremely elevated ESR (>100)?
Infection
Malignancy (particularly multiple myeloma)
Renal conditions (end-stage renal failure, nephrotic syndrome)
Inflammatory disorders (particularly temporal arteritis/polymyalgia rheumatica)
What is the most common cause of elevated CRP?
Infection
Which conditions is ESR useful in the diagnosis of?
Temporal arteritis
Polymyalgia rheumatica
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