PILM- Clinical Biochem

what is clinical biochemistry

A branch of laboratory medicine used to study disease through the testing of blood, urine and other bodily fluids

• studies chemicals and biochemical processes in the bod using these samples

how are biochemical testes used in the medical feild

Biochemical tests can be used for

• diagnosis: confirming or rejecting

• treatment/monitoring the progression of a disease/ response to treatment

• prognosis: inferring disease outcome

• screening: detection of subclinical(early stage) disease

name the general types of test done in clinical biochemistry

• Measures the level of certain substances in the body, like glucose, vitamins or minerals (biomolecules)

• Detects non-functional metabolites or metabolic waste products like creatinine, blood urea or nitrogen

• Detect substances that indicate cell damage, like liver enzymes

what is the overal testing process as a medical scientist

1. Patient goes to a clinician who orders a test

2. Patient is then prepped and the required sample is taken ( blood, urine, CF, tissue)

3. Sample is sent to the lab where tests are performed

4. Results are analysed and put into a report that is sent to the clinician

what are some areas of errors that can be made in the testing process

• postanalytical errors ( wrong sample, mislabbeling, issues with collection or transport) 60-70% of error

• analytical error ( Human or instrument error) 10-20% of error

• post- analytical error ( incorrect recording of results) 10-20% of error

what does the pre-analytic stage of clinical chem include

includes the requesting of a test, preparing of a patient, timetabling collection, identifying patient, collecting sample, transporting sample and storing samples

what types of spceimens can be used in clinical biochem

Most common include

• whole blood/serum/plasma

• Urine

• CSF

Less common include

• amniotic fluid (for newborn babies)

• gastric juices

• kidney stones

• saliva

• tissue specimens

• gall stones

• stools

• synovial fluid

what are some errors that can occur in blood collection

• incorrect used of blood storage tubes leading to blood clotting(wrong tube, not enough blood, no mixed enough)

• incorrect use of tourniquet stops or slow blood flow too much to the point of decreasing blood cell concentration (too much plasma)

• improper storage of the sample after taking or during transport ( high temps can kill blood cells effecting cell counts)

• improper sampling site leading to possible contamination of sample

• improper timing (delays in transport or patient didn’t fast)

• mislabeling

what is blood plasma and when is it used

the fluid portion of blood centrifuged from unclotted whole blood

• contains water, proteins, carbs, lipids, vitamins and minerals ( + clotting factors)

• to collect we use a tube with an anticoagulant

• used ofr coag studies in heamotology, blood gass tests and special assays

what is blood serum and when is it used

the fluid portion of blood the sperate when centrifuged fron clotted whole blood

• contains same stuff as plasma but with no cltting factors

• used for immunology, serology and drug tests

when is whole blood required

Whole blood will also contain WBCs, RBCs, and platelets and can be used for

• hemoglobin levels

• RBC folate

• blood gas content ( needs to be heparinised)

what are vacutainers

Evacuated test tubes that are sterile, easy to use and contain vacuums for easy collection

• are universally colour-coded depending on what they contain

what do the differnt colour vacutainers contain

• red ( nothing, used for serum samples)

• Gold ( contains SST gel used for serum separation)

• blue ( contains sodium nitrate for coag tests)

• green (contains lithium, heparin, electrolyte and more for quick plasma testing)

• white (contains fluoride, oxalate, glucose and lactate to prevent glycolysis)

• purple ( contains EDTA FBC and HbA1C to preserve blood cells)

what does the analytical phase of testing require

• Identifying sample and what tests need to be done

• calibrating instruments

• quality control checks

• measuring analytes

• validating results

what are the three types of clinical chem facilities

Core laboratory facilities found in hospitals that are open 24/7 and perform essential or most frequently ordered tests

• will often be very automated, with equipment that can perform multiple tests

Special chemistry labs do more manual labour-intensive tests that are less frequently ordered

• results aren’t required immediately

Point-of-care testing uses instruments to perform simple tests bedside or in pop-up clinics

what is automated in a core lab

Machinery in core labs used a barcode system to identify different samples and complete all measuring and mixing of samples and reagmts automatically

• needs to be loaded and tests are chosen by the worker

• can perform immunoassays, ion-selective electrodes and spectrophotometry

what types of tests are done in core labs

• electrolyte tests (Na, K, Cl)

• blood gases

• thyroid hormones

• cholesterol, LDL or HDL

• protein

• glucose'

• tumour markers

• vitamin/mineral levels

• alcohol and drug levels

• urea and creatinine levels for renal function

what is a special chem lab

Does fewer tests have to be done by hand and don’t need immediate results

• staff require more training than core labs

• only found in larger hospitals

• uses more expensive equipment

• needs more specimens to justify the use of resources and money on a test

what techniques are used in a special chem lab

• electrophoresis ( for protein separation)

• HPLC for measuring alcohol, vitamin and catecholamine levels)

• infrared spectroscopy ( used to analyse kidney stones)

• immunoassay ( detecting hormones or biomarkers)

• mass spectroscopy ( drug level measurements)

what can be done using point of care testing

• blood glucose levels

• urinalysis

• blood gases

• electrolytes/ creatinine

• cardiac markers for signs of heart attack

• coag tests

advantages and diadvatages of point of care testing

pros

• quick resulyts allow for quicker and easier clincal decison making that get patient care quicker

cons

• much more expensive per test

• requires more quality control testing

how can patient results be validated before

Results can be validated using quality control measures throughout testing

• first machine is calibrated using samples of known concentration

• then we run control sample of known concentration through to see how accurate the machine is

what are some possible causes of error in the analytical phase

errors can be either procedural:

• variability in accuracy between instruments

• incorrect calibration or maintenance

• contamination

• quality control failure

• reagent instability

or human error

• protocol errors due to change in test operator

• inaccurate analysis or calculations

• identification error

• inattention leading to overlooked results

what does the post-anayltical phase involves

Include generating a report, applying correct refernce ranges, communicating critical results clearly and sending off the report to the clinician

what are the three questions used to interpret resulst

• is the result normal? ( compare using reference values)

• is the result different to previous results ( consider past resulst or bilogica/analytical variations)

• is the results consistent with clinical findings ( compare with patient finding)

what are refernce values

a range for a result that is expected in health induvidual or in normal physiology

• Results outside these values can indicate possible disease

• values can differ depending on gender, age, other conditions, race, pregnancy

• Small amounts over or under reference don’t nesscesairly indicates disease

what are some forms of biological and analytical variation

Biological: sex, age, diet, time, stress levels, exercise, pregnancy

analytical: variation in repeated analysis of the same sample that could indicate the results are inaccurate

how to determine if finding correlate with clinical findings

Look at patient history, clinical findings, and findings from other tests (pathological or imaging)

• unexpected results may require retesting and examination of protocol for possible errors

sources of error in post analytics

error in post-analytic can lead to misdiagnosis, incorrect treatment or inadequate follow-up

• can be data entry error, incorrect analysis, worng patient or faliure to communicate critical results

what are some general professional responsibilities in a lab setting

• Following standard procedures

• maintaining competency and keeping up education

• understanding possible sources of error

• promote patient safty above all