Organ Function Testing, Screening and Therapeutic Drug Monitoring Uses of biochemical tests · Diagnosis o 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 conc of that protein and correlate it to the progression of the disease. E.g. HIV- number of virus particles is a good way of telling if person has HIV o Diagnosis will allow for bellow: · 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. o Screening is the use of a biochemical test otherwise healthy individuals- looking for indv who are at increased risk of developing disease/ asymptomatic carriers of it. o Population - new-born screening. o Selected group - obese patients for type II diabetes mellitus. o Individual - familial hypercholesterolaemia. · Biomarkers o Biochemical tests are identifying biomarkers. Naturally occurring molecule, gene or characteristic by which a particular pathological disease can be identified. o Usually measured in blood but can be in sweat urine, faeces or CSF. Bld samples are easy, inexpensive CSF, precious, painful but necessary for identifying diseases like meningitis o Biomarkers can be enzymes, metabolites, or hormones. They tend to be metabolites when a disease specifically alters a biological mechanism- increase in by product as a result of the disorder Hormone example - insulin in diabetes or excess growth hormone in acromegaly · (rare cases) can also be lons or gases are often also measured in Clinical Biochemistry Serum proteins/ enzymes as biomarkers · In normal tissue the cell membrane is intact and enzyme escapes due to normal cell turnover. · When the membrane is damaged high levels of enzyme are released o Disease damages cell membrane = leaky= enzyme inside tissue leaks into blood= high conc in blood · Problems with this approach · Increased cell number increases serum enzyme activity. o There are natural instances of cell proliferation (hyperproliferation) /cell turnover o More growth naturally means more cell death = falsely elevated level of enzyme in blood o could also be due to use of certain meds o · Induction of enzyme within a tissue increases release
o An external event may lead to increase expression/conc of certain enzyme o i.e. too much alcohol-liver upregulates production of alcohol dehydrogenase as a compensatory mechanism- this ofc does not mean liver is damaged through sorosis etc o some instances of induction can be diagnostically useful i.e. albumin- it is abundant in the body and there can be numerous, non-serious reasons why it is elevated So what makes an ideal biomarker? · Tissue specific (i.e. only present within one tissue). o So that you