Investigations Flashcards
What is a full blood count (FBC)?
Is a measure of the different constituent cells of the blood sample.
Why might you request a full blood count?
To look for anaemia- may be found in chronic inflammatory conditions or with blood loss from trauma. Normocytic anaemia usually indicates acute blood loss or chronic inflammation. Microcytic anaemia is found in iron-deficient states, such as that caused by non-steroidal anti-inflammatory drugs (NSAID) use with chronic gastrointestinal blood loss. Haemolytic anaemia can occur as a result of autoinflammatory disease and is typically microcytic anaemia.
High white cell count = infection, inflammation or due to steroid use
Leukopenia - can be a feature of SLE, connective tissue disease or bone-marrow suppression from antirheumatic drugs.
Thrombocytosis - often occurs in active inflammatory disease, in that case= reactive thrombocytosis. Thrombocytopenia can be seen in SLE and antiphospholipid syndrome.
What is ESR?
Erythrocyte sedimentation rate- is the rate at which red blood cells sediment over an hour and is a marker of inflammation.
When does the measurement for ESR increase and when does the upper limit for ESR increase?
The measurement increases with higher levels of plasma proteins such as immunoglobulins and fibrinogen.
The upper limit of ESR increases with advancing age and in overweight women.
What is CRP?
C-reactive protein- is an acute-phase protein that is manufactured in the liver.
How do the levels of CRP rise?
Its levels rise in a non-specific way as a result of inflammation and infection.
How long does it take for CRP to rise after an inflammatory event?
6-10 hours
CRP responds more rapidly than ESR to changes to inflammation
Why might you request for urea and electrolytes in a blood test?
Renal impairment may occur in gout or connective tissue disease.
NSAIDs can cause interstitial nephritis.
Why would you request a LFT?
To check if alkaline phosphatase is seen in Paget disease
Some drugs are hepatotoxic e.g. methotrexate & sulfasalazine and require routine monitoring.
Why would you request for uric acid in a blood sample?
Uric acid levels = high in gout
Normal levels during an attack of gout
Why would you request for calcium serum in a blood test?
Low levels = hypocalcemia occurs in osteomalacia and vitamin D deficiency.
High levels = hypercalcemia can be a feature of malignancy, sarcoid, and excess parathyroid hormone production.
What is creatine kinase?
is a muscle enzyme that increases in response to a muscle injury that increases in response to muscle injury (trauma, hypoperfusion or inflammation)
What is procalcitonin?
when a patient’s joint is hot. It can be useful in combo with ESR, CRP, and the FBC to establish whether patients have joint infections or joint inflammation.
Why would you request for procalcitonin?
High procalcitonin is indicative of bacterial infection and sepsis.
What is RF?
Rheumatoid factor is an antibody directed against the Fc fragment of human immunoglobulin G (IgG). It may be of any class, but IgM anti-IgG is the most commonly measured.
