introduction to understanding blood science results Flashcards
why are lab results important
70% clinical decisions informed by data from laboratory science (less than 5% of NHS budget)
why might a lab test be requested
Screen for disease Risk stratification Diagnose disease Prognosis Monitoring progress/remission of disease Monitoring therapy - Therapeutic drugs or side effects of treatment
what are the 4 main divisions of pathology
Histology and cytology
Bacteriology and virology
Haematology
Biochemistry and immunology
what is Histology and cytology
tissue diagnosis (malignancy, infection, auto-immune)
what is Bacteriology and virology
causes of infection – culture, antigen and antibody testing, increasingly PCR and antibiotic use, public health and environmental testing)
what is Haematology
diseases of the blood, transfusion, coagulation
what is biochemistry and immunology
measurement of analytes in blood, urine, CSF etc
What types of samples are analysed in clinical chemistry
Serum Whole blood Urine Faeces Sweat Cerebrospinal fluid Renal stones Post-mortem samples Miscellaneous fluid
what is measured in the lab
Ions Metabolites Waste/breakdown products Markers of cell damage Enzymes Plasma proteins Antibodies Hormones Drugs Vitamins Metals
what can cause an issue in analysing chemicals
very similar so can pose an issue eg cholesterol or testosterone
what does a renal function test for
Na, K, urea and creatine
what does a liver function test for
total protein, albumin, bilirubin, alkaline phosphatase and alanine transaminase
what does a bone profile test for
total protein, albumin, ca, phosphate, alkaline phosphatase
what does a thyroid function test for
TSH (Free T4 and T3)
what does a lipid profile test for
total cholesterol, HDL, non HDL and triglycerides
what do lab reports typically contain
the analyte, the result, the units, a flag and a ref range
what is a reference range
Guide to help interpret results
how are reference ranges generated
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
how are reference ranges interpreted
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
are reference ranges always the same
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)
can reference ranges vary
Reference ranges vary between labs, depend on method analysis and are updated so don’t need to memorise only be familiar
how many fit in the reference ranges
95% within reference ranges
- 5% lower
- 5% higher
