introduction to understanding blood science results

Question 1

why are lab results important

Answer 1

70% clinical decisions informed by data from laboratory science (less than 5% of NHS budget)

Question 2

why might a lab test be requested

Answer 2

Screen for disease
Risk stratification
Diagnose disease
Prognosis
Monitoring progress/remission of disease
Monitoring therapy - Therapeutic drugs or side effects of treatment

Question 3

what are the 4 main divisions of pathology

Answer 3

Histology and cytology
Bacteriology and virology
Haematology
Biochemistry and immunology

Question 4

what is Histology and cytology

Answer 4

tissue diagnosis (malignancy, infection, auto-immune)

Question 5

what is Bacteriology and virology

Answer 5

causes of infection – culture, antigen and antibody testing, increasingly PCR and antibiotic use, public health and environmental testing)

Question 6

what is Haematology

Answer 6

diseases of the blood, transfusion, coagulation

Question 7

what is biochemistry and immunology

Answer 7

measurement of analytes in blood, urine, CSF etc

Question 8

What types of samples are analysed in clinical chemistry

Answer 8

Serum
Whole blood
Urine
Faeces
Sweat
Cerebrospinal fluid
Renal stones
Post-mortem samples
Miscellaneous fluid

Question 9

what is measured in the lab

Answer 9

Ions
Metabolites
Waste/breakdown products
Markers of cell damage
Enzymes
Plasma proteins
Antibodies
Hormones
Drugs
Vitamins
Metals

Question 10

what can cause an issue in analysing chemicals

Answer 10

very similar so can pose an issue eg cholesterol or testosterone

Question 11

what does a renal function test for

Answer 11

Na, K, urea and creatine

Question 12

what does a liver function test for

Answer 12

total protein, albumin, bilirubin, alkaline phosphatase and alanine transaminase

Question 13

what does a bone profile test for

Answer 13

total protein, albumin, ca, phosphate, alkaline phosphatase

Question 14

what does a thyroid function test for

Answer 14

TSH (Free T4 and T3)

Question 15

what does a lipid profile test for

Answer 15

total cholesterol, HDL, non HDL and triglycerides

Question 16

what do lab reports typically contain

Answer 16

the analyte, the result, the units, a flag and a ref range

Question 17

what is a reference range

Answer 17

Guide to help interpret results

Question 18

how are reference ranges generated

Answer 18

Take a large number of healthy individuals, measure substance of interest and calculate mean and standard deviation of the results
The reference range is mean and 2sd either side

Question 19

how are reference ranges interpreted

Answer 19

In general results outside the reference range does not necessarily imply disease (could be a health outlier with an extreme value) and results inside do not necessarily exclude disease

Question 20

are reference ranges always the same

Answer 20

Sometimes there’s one reference range regardless of age, sex etc but for some things there are a variety of different ranges
Eg testosterone ref range in males is higher than in females
Eg creatinine in males, females and children varies with age as its linked to muscle mass
One enzyme may have many sources
Eg alkaline phosphatase – related to bone growth and turnover (higher in children, esp puberty)
Liver, bone, intestine, kidney placenta
Some things can change in pregnancy eg serum thyroid hormone concentrations (varies in each trimester)

Question 21

can reference ranges vary

Answer 21

Reference ranges vary between labs, depend on method analysis and are updated so don’t need to memorise only be familiar

Question 22

how many fit in the reference ranges

Answer 22

95% within reference ranges

2. 5% lower
3. 5% higher