Inflammatory markers

Question 1

What does Erythrocyte sedimentation rate (ESR) measure?

Answer 1

Measures rate at which red blood cells sediment over an hour.

A marker of inflammation.

Measurement increase w/ higher levels of plasma proteins in the blood e.g. immunoglobulins and fibrinogen.

The upper limit of ESR increases w/ age & in overweight women.

Question 2

How can ESR confirm diagnosis of certain conditions?

Answer 2

Good for MSK conditions that involve inflammation e.g. septic arthritis, SpAs, RA, Osteomyelitis

Question 3

Explain how ESR test works?

Answer 3

1. Blood is placed in tall, thin tube.
2. Red blood cells (erythrocytes) gradually settle to the bottom of tube.
3. Inflammation causes the cells to clump - as the clumps are denser than individual cells, they settle to the bottom more quickly.
4. The further the red blood cells have descended in an hour, the greater the inflammatory response.

Question 4

What are the limitations of ESR?

Answer 4

• Test cannot pin-point cause of the inflammation, so other blood tests are needed e.g. CRP.
• A number of conditions can alter properties of blood, therefore affecting how quickly red blood cells sink in sample.

E.g. advanced age, anaemia, pregnancy, kidney problems & thyroid infection.

Question 5

What is CRP?

Answer 5

An acute phase protein produced in the liver.

Its levels rise when there is an infection or inflammation in the body.

CRP enters bloodstream from liver during inflammation.

Takes 6-8 hours after inflammatory event to increase - responds faster than ESR to changes in inflammation.

Question 6

What are the limitations of CRP?

Answer 6

• CRP test does not explain the cause or location of the inflammation.
• CRP may be normal in autoimmune connective tissue disease e.g. SLE & systemic sclerosis. BUT ESR is high.
• Elevated levels of CRP in patients w/ Lupis or systemic sclerosis suggests an intercurrent illness e.g. sepsis, rather than an active disease.

Question 7

What’s plasma viscosity?

Answer 7

• Similar to ESR.
• Measures the viscosity/ thickness of plasma
• Viscosity of plasma is affected by presence of proteins- fibrinogen- that are produced in a normal response to infection or inflammation, or proteins that are produced abnormally in certain diseases (paraproteins).

-Many conditions can cause an increase in PV: RA, SLE, psoriatic arthritis, Sjogren’s, inflammatory bowel disease, liver disease & HIV.

Question 8

What does Full blood count(FBC) measure?

Answer 8

Measures the different constituent cells of a blood sample.
- Red blood cells
- White blood cells
- Haemoglobin
- Platelets

Question 9

What does low haemoglobin indicate?

Answer 9

Indicates anaemia.

Caused by low levels of iron & certain vitamins, blood loss (due to trauma-not always) or chronic inflammatory conditions.

Causes fatigue & weakness.

Normocytic anaemia - when you have normal- sized red blood cells, but you have a low number of them - indicates acute blood loss or chronic inflammation.

Microcytic anaemia - when blood cells are smaller than normal - is found in iron deficient states (e.g. use of NSAID’s w/ chronic gastrointestinal blood loss).

Macrocytic anaemia - when red blood cells are abnormally large, but there is a low number of them - causes haemolytic anaemia, result of autoinflammatory disease.

Question 10

What does high red blood cell count or high haemoglobin indicate?

Answer 10

• High in active inflammatory disease.
• Can also point to underlying conditions e.g. heart disease

Question 11

What does high white blood cell count?

Answer 11

High white cell count can be due to inflammation, infection, or steroid use.

Neutrophilia (high neutrophil count) is seen in crystal arthrites & sepsis.

Question 12

What does low white blood cell count indicate?

Answer 12

• Low white cell count (leukopenia) can be caused by autoimmune disorder that destroys white blood cells, bone marrow suppression, connective tissue disease or cancer.
• A normal or low white cell count does not exclude infection - patients who are immunosuppressed, or the elderly, often present in this way.
• Neutropenia (low neutrophils) are seen in SLE.

Question 13

What does high platelet count indicate?

Answer 13

A high platelet count (thrombocytosis) occurs in active inflammatory disease - called reactive thrombocytosis.

Question 14

What does low platelet count indicate?

Answer 14

Low platelet count (Thrombocytopenia) is seen in SLE & antiphospholipid syndrome.

Question 15

What does Uric acid test measure?

Answer 15

• Measure the amount of uric acid in blood or urine.
• Uric acid is waste product when body breaks down chemicals called purines - purines are found in cells & in some food.
• Test can be done either as blood test or urine test.

Question 16

What does uric acid test help diagnose? What does high levels in blood & urine indicate?

Answer 16

• High in patients w/ gout but can be normal during an attack of gout.
• High uric acid can also cause kidney stones & kidney failure.
• High levels of uric acid in blood test can be due to kidney disease or diet that contains too many purine-rich food, whereas low levels are uncommon.
• High levels of uric acid in urine test can indicate gout, leukaemia, obesity or diet that contains too many purine-rich food, whereas low levels can indicate kidney disease.

Question 17

What is Rheumatoid Factor? What does it indicate? False positive test?

Answer 17

Rheumatoid factor is an antibody directed against the Fc fragment of human immunoglobulin G (IgG).

• IgM-anti IgG is most commonly measured.
• Around 75% of patients w/ rheumatoid arthritis have a positive rheumatoid factor antibody.
• Rheumatoid factors are proteins produced by immune system that can attack healthy tissues in the body.
• May be detected in healthy individuals or people w/ autoimmune diseases sometimes have normal levels of rheumatoid factors- makes it less accurate.
• Other diseases, that can have high levels of RF: cancer, chronic infections, inflammatory lung disease, Sjogren syndrome & SLE.

Question 18

What is anti-CCP? What does it indicate? What is it associated with?

Answer 18

Anti-CCP= an antibody found in patients w/ rheumatoid arthritis.

More specific than rheumatoid factor- when strongly positive, it has a high predictive value in the risk of developing RA.

associated w/ increased risk of joint erosions.
- Can cause disease by attacking the body’s healthy cell- specifically target tissue in joints.

Done alongside rheumatoid factor test.

Normal levels of anti-CCP is less than 20 units.

Question 19

What is Antinuclear antibodies (ANA)? What does a positive result indicate?

Answer 19

• ANAS’ are antibodies to nuclear antigens (target the nucleus).
• Detected in blood using labelling methods such as indirect immunofluorescence.
• A positive ANA means that there are antibodies present in blood that will bond to a sample cell used in the test.
• If ANA is positive- important to examine which nuclear antigens the antibodies bind to.
• significance of the positive result is increased if the antibody is detectable after multiple dilutions

Question 20

What is synovial fluid analysis? Normal fluid?

Answer 20

• Most useful test for investigating potential cases of septic or crystal arthritis.
• Synovial fluid can be aspirated from most peripheral joints.
• Normal fluid= pale yellow color.