Organ Function Testing Learning Outcomes: . How do Biomedical Scientists use biochemical tests? · How do we identify abnormal results? · How good is a particular test at providing a diagnosis? · How does population screening work? · What is therapeutic drug monitoring? Uses of biochemical tests . Diagnosis - i.e. If you know a protein is present in the blood after the organ is deteriorating, you can run a test to quantify the concentration of that protein and correlate it to the progression of the disease. E.g. HIV- number of virus particles are a good way of telling if person has HIV. · Management. o Progression of disease - Is it improving? . Do meds need changing? o Response to treatment . i.e. HIV- patient has high viral load, can quantify that viral load to see how it's decreasing in line with treatment. o Recurrence of disease - . Once drug is administered, another blood sample should be taken a while later to see if the viral load has increased for example. · Screening - detection in asymptomatic individuals. Screening is the use of a biochemical test otherwise healthy individuals- looking for individuals who are at increased risk of developing disease/ asymptomatic carriers of it. o Population - newborn screening. o Selected group - obese patients for type II diabetes mellitus. o Individual - familial hypercholesterolaemia. Biomarkers " Biochemical tests use biomarkers (biomarkers are natural occurring molecule/gene/ chrematistic in which a particular pathogenic disease/pathway can be identified) " Usually measured in blood but can be in urine, faeces, or CSF. - Blood samples are easy, inexpensive (advantage) - CSF - found in the brain and spinal cord- difficult to retrieve, taken from lower region of the spine if needed. - CSF, precious, painful but necessary for identifying diseases like meningitis · Biomarkers can be enzymes, metabolites, or hormones. - tend to be metabolites when a disease alters a biological mechanism - increase in byproduct - hormones; type II diabetes - disregulations of insulin, excess growth hormone in acromegaly " lons or gases are often also measured in Clinical Biochemistry. (rare cases)
Serum proteins / enzymes as biomarkers Blood " In normal tissue the cell membrane is intact and enzyme escapes due to normal cell turnover. Tissue Enzyme . When the membrane is damaged high levels of enzyme are released - disease damages cell membrane = leaky = enzyme inside tissue leaks into blood = high concentration in blood " Are there any problems with this approach? Enzyme - Increased cell number increases serum enzyme activity. - There are natural instances of cell proliferation (hyperproliferation) /cell turnover - More growth naturally means more cell death = falsely elevated level of enzyme in blood - could also be due to use of certain meds - Increased cell number increases serum enzyme activity (leads to false increase) - Induction of enzyme within a tissue increases release. - when an external event causes an increase the conc. of the enzyme (e.g. too much