Infection Tests Flashcards
What is the first most important step when diagnosing an infection?
History
Symptoms suggestive of infection can be “system specific” or “non-specific”.
What are examples of system specific symptoms?
Cough (*respiratory) Neck stiffness (*CNS) Bony pain (*orthopaedic) Skin pain/redness (*SST) Dysuria (*urinary)
What are examples of non specific symptoms?
Fever “burning up”
Shaking episodes/chills
Sweating/night sweats
Feeling muddled/confused
When symptoms suggest a diagnosis of infection other information can help identify potential pathogens.
What questions should be asked?
- Travel?
- Inside Uk
- Outside Uk (detail) - Occupation?
- Farmer, fishmonger, vet, air steward etc - Animal contact?
- Which animal(s)/nature of contact - Hobbies/past times?
- Sexual history?
What is considered as a fever/high temperature?
Temperature >38.0 C
What are general symptoms of infection?
Fever “burning up”
Chills, sweats, night sweats
Rigors
Examination findings can also be “system specific” or “non-specific”.
What are examples of system specific examination findings?
Lung crackles (*respiratory) Meningism (*CNS) Bony tenderness (*orthopaedic) Skin erythema (*SST) Loin tenderness (*urinary)
What are examples of non specific examination findings?
Pyrexia
Witnessed rigor/chills
Sweating
Confusion
What components of the blood are tested in a full blood count?
- RBCs
- WBCs
- Platelets
- Hb
Normocytic vs normochromic anaemia?
Normocytic anaemia: when the RBCs are of normal size
Normochromic anaemia: when conc of Hb is normal but insufficient RBCs
Is a FBC useful in infection testing?
Not really:
Hb: Not much help diagnosing infection – but anaemia of chronic disease (normocytic, normochromic) can be caused by infection
WCC: can be raised in infection, but other conditions too (poor specificity). Severe sepsis can lower WCC
How does severe sepsis affect WCC?
Reduces it
In a bacterial infection, describe the:
a) WCC
b) lymphocytes
c) neutrophils
a) raised
b) normal or low
c) raised
In a viral infection, describe the:
a) WCC
b) lymphocytes
c) neutrophils
a) normal
b) raised
c) normal
COVID-19 is an exception. Describe the:
a) WCC
b) lymphocytes
c) neutrophils
a) decrease
b) decrease
c) increase
What are inflammatory markers?
Elements of the innate immune system:
a) C-reactive protein
b) Procalcitonin
What is procalcitonin?
Procalcitonin (PCT) is the precursor of the hormone calcitonin, which in normal metabolic conditions is mainly produced by the C‐cells of the thyroid medulla.
The blood of healthy individuals contains only very low levels of PCT.
Describe PCT levels during bacterial infection
The level of PCT increases in response to a pro-inflammatory stimulus, especially of bacterial origin.
The high PCT levels produced during infection are not followed by a parallel increase in calcitonin or serum calcium levels.
What does an increase in PCT suggest?
Can be serious bacterial infections
What is CRP?
C-reactive protein is a substance produced by the liver in response to inflammation.
What would cause an increase in CRP?
CRP levels can arise when you have a viral infection. But they don’t go as high as during a bacterial infection (PCT more useful for this)
What is lung consolidation?
Occurs when the air that usually fills the small airways in your lungs is replaced with something else. Depending on the cause, the air may be replaced with: a fluid, such as pus, blood, or water. a solid, such as stomach contents or cells.
Which organ is responsible for the major part of lactate metabolism?
Liver
What can high blood lactate levels indicate?
Inadequate oxygen delivery and tissue hypoxia results in increased lactate generation:
- Strenuous exercise
- Severe infection (sepsis)
- Shock
- Heart failure
- Respiratory failure
These conditions lower the flow of blood and oxygen throughout the body.
