Urine & Diagnosis
This lesson covers:
- The use of urine samples for medical diagnosis
- The use of urine samples for pregnancy testing
- The use of urine samples for drug detection
The use of urine samples for medical diagnosis
Urine contains water, urea, mineral salts, hormones, toxins, and various breakdown products. The composition of these substances in urine can provide crucial clues about different medical conditions.
Some key indicators of medical conditions found in urine:
- The presence of glucose in urine often indicates diabetes.
- Elevated levels of creatinine in urine may suggest muscle damage.
- The presence of blood or proteins in urine may signal kidney disorders.
Urine tests are valuable as they allow doctors to diagnose and monitor diseases without using more invasive procedures.
The use of urine samples for pregnancy testing
Human chorionic gonadotropin (hCG) is a hormone that is produced by the placenta after an embryo implants into the uterus. The presence of hCG in a person's blood or urine is therefore a sign that they are pregnant.
Modern pregnancy tests use monoclonal antibodies that specifically target hCG. Monoclonal antibodies are antibodies from a single clone of identical cells that are produced to target particular cells or chemicals in the body.
How modern pregnancy tests work
Modern pregnancy tests are highly sensitive, and some can detect pregnancy within hours of conception.
How pregnancy tests work if someone is pregnant:
- The wick of the test is soaked in urine, which if a person is pregnant will likely contain the hormone hCG.
- Mobile monoclonal antibodies attached to coloured beads bind to hCG to form an antibody-hCG complex.
- Urine carries this complex to a window with immobilised monoclonal antibodies that only bind to the antibody-hCG complex.
- This creates a coloured line or symbol, like a plus sign, indicating pregnancy.
- Other immobilised antibodies bind to mobile antibodies with or without hCG, forming a control line to confirm the test is working.
If the person is not pregnant, only the control line will appear in the window.
The use of urine samples for drug detection
Drugs are filtered through the kidneys and stored in the bladder before their removal from the body during urination. This means that urine will typically contain evidence of any drugs that a person has used. So, urine samples can be used to test for the presence of drugs or their breakdown products.
Some examples of drugs that may be tested for include:
- Anabolic steroids - These drugs mimic the action of the sex hormone testosterone to stimulate the growth of muscles, and are sometimes illegally used by athletes to boost performance.
- Recreational drugs - Some illegal recreational drugs like cocaine can also be tested for using urine samples.
How drug tests work
A non-invasive approach of testing urine for drugs can have a significant impact on addressing drug misuse issues.
How urine drug tests work:
- Carry out an immunoassay, where monoclonal antibodies bind to a substance, such as a drug or its breakdown products, to indicate whether a urine sample contains them.
- Vaporise the urine sample with a known solvent.
- Separate the components of the sample using gas chromatography.
- Use mass spectrometry to identify the molecular structures in the sample.