Clinical Chemistry:
Clinical chemistry is a type of analytical, wet chemistry that involves the analysis of body fluids in a clinical setting for the diagnosis and treatment of diseases or conditions or to rule them out. It is a type of applied biochemistry and clinical pathology. Laboratories can be in hospitals or clinics, research centers, outreach centers, large corporations, public health or specialty testing centers.
Simple chemical reaction tests are performed on blood and urine to test them. Clinical chemistry is highly automated but carefully analyzed and monitored by medical laboratory scientists, technologists and technicians for Quality Control. Most tests are performed on urine, body fluids, and especially blood. There are some whole blood tests, but most chemistry tests require the fractionation of blood, resulting in packed cells at the bottom, and serum or plasma on top.
Serum is the straw-to-amber colored fluid portion of the blood that is found at the top of the tube after it has been allowed to clot (30-60 minutes) and the cells have been removed. This is typically performed by centrifugation, which causes the denser red blood cells to tightly pack at the bottom, and the white blood cells and platelets to form a thin layer in the middle, leaving the serum or plasma at the top. Serum contains all the components of plasma without the clotting factors. They were consumed during the cascade that occurred when the clot formed. Plasma is the liquid portion of the blood without allowing it to clot first, also obtained from centrifugation. Plasma is collected from a tube containing an additive to prevent the blood from clotting (an anticoagulant). The fluid portion left after centrifugation is the plasma. It contains clotting factors.
Additives are either anticoagulants that prevent the blood from clotting OR substances added to prevent analytes from breaking down chemically or metabolically.
General or routine chemistry involves basic general blood tests, such as the basic metabolic panel, comprehensive metabolic panel, liver panel, renal panel, blood sugar, electrolytes, etc...
Special chemistry testing involves drug testing, toxicology (drug and alcohol abuse), testing for metals, and may involve sending the specimen out to a specialty lab for that type of testing. It also includes electrophoresis.
Clinical endocrinology testing is the testing of hormones and the endocrine glands, such as the thyroid and parathyroid glands.
Therapeutic drug monitoring is testing for troughs, or levels of therapeutic drugs in the blood, to make sure that patients are getting the correct dosage for their individual needs.
Urine and body fluids testing includes timed urine testing for various analytes, such as total protein, creatinine, BUN, GFR, and testing body fluids such as CSF, pleural or peritoneal fluids for proteins, enzymes, glucose, etc...
Simple chemical reaction tests are performed on blood and urine to test them. Clinical chemistry is highly automated but carefully analyzed and monitored by medical laboratory scientists, technologists and technicians for Quality Control. Most tests are performed on urine, body fluids, and especially blood. There are some whole blood tests, but most chemistry tests require the fractionation of blood, resulting in packed cells at the bottom, and serum or plasma on top.
Serum is the straw-to-amber colored fluid portion of the blood that is found at the top of the tube after it has been allowed to clot (30-60 minutes) and the cells have been removed. This is typically performed by centrifugation, which causes the denser red blood cells to tightly pack at the bottom, and the white blood cells and platelets to form a thin layer in the middle, leaving the serum or plasma at the top. Serum contains all the components of plasma without the clotting factors. They were consumed during the cascade that occurred when the clot formed. Plasma is the liquid portion of the blood without allowing it to clot first, also obtained from centrifugation. Plasma is collected from a tube containing an additive to prevent the blood from clotting (an anticoagulant). The fluid portion left after centrifugation is the plasma. It contains clotting factors.
- Some chemistry tests are performed on plasma.
- Some chemistry tests are performed on serum.
- Some chemistry tests can be performed on either one.
Additives are either anticoagulants that prevent the blood from clotting OR substances added to prevent analytes from breaking down chemically or metabolically.
General or routine chemistry involves basic general blood tests, such as the basic metabolic panel, comprehensive metabolic panel, liver panel, renal panel, blood sugar, electrolytes, etc...
Special chemistry testing involves drug testing, toxicology (drug and alcohol abuse), testing for metals, and may involve sending the specimen out to a specialty lab for that type of testing. It also includes electrophoresis.
Clinical endocrinology testing is the testing of hormones and the endocrine glands, such as the thyroid and parathyroid glands.
Therapeutic drug monitoring is testing for troughs, or levels of therapeutic drugs in the blood, to make sure that patients are getting the correct dosage for their individual needs.
Urine and body fluids testing includes timed urine testing for various analytes, such as total protein, creatinine, BUN, GFR, and testing body fluids such as CSF, pleural or peritoneal fluids for proteins, enzymes, glucose, etc...
Common Clinical Chemistry Panels:
Electrolytes:
- Sodium (Na+)
- Potassium (K+)
- Chloride (Cl-)
- Bicarbonate
Minerals:
- Calcium
- Magnesium
- Phosphate
- Potassium
Blood Disorders/Anemias:
- Iron
- Transferrin
- Haptoglobin
- TIBC
- Vitamin D25
- Vitamin B12
- Folate/Folic Acid
- Ferritin
Cancer/Tumor Markers:
- CA-235
- CA 15-3
Renal (Kidney) Function Tests:
- Creatinine
- Blood Urea Nitrogen (BUN)
Hepatic (Liver) Function Tests:
- Total protein
- Albumin
- Globulins (IgG, IgM, IgA)
- Protein electrophoresis
- Urine protein
- Direct bilirubin
- Total bilirubin
- Indirect bilirubin
- Aspartate Transaminase (AST)
- Alanine Transaminase (ALT)
- Gamma-Glutamyl Transpeptidase (GGT)
- Alkaline Phosphatase (ALP)
Diabetes:
- Insulin
- GHGB/Hemoglobin A1C
Cardiac Markers:
- Troponin
- BNP
- CKMB
- CKP
Thyroid Panel:
- TSH/TSHR
- Free T4 (FT4)
Hepatitis Panel (HEP ACUTE):
- Hepatitis B Surface Antibody
- Hepatitis B Surface Antigen
- Hepatitis C Antibody
- Hepatitis A IgM
- Hepatitis Core IgM
- Hepatitis Core Total (IgG)
Basic Metabolic Panel:
- 8 tests - sodium, potassium, chloride, bicarbonate, blood urea nitrogen (BUN), creatinine, glucose, calcium
Comprehensive Metabolic Panel:
- 14 tests - above BMP plus total protein, albumin, alkaline phosphatase (ALP), alanine amino transferase (ALT), aspartate amino transferase (AST), bilirubin
Vacutainer Tubes:
Vacutainer tubes are evacuated tubes used with the ETS and syringe method of gathering blood specimens. If blood is collected in a syringe, it is immediately transferred to the tubes, and butterflies used to obtain blood are transferred with a transfer device. Vactainer evacuated tubes automatically fill with blood because there is a vacuum created by negative pressure within them, which creates the vacuum when air is pulled from the tube. The tube is designed to draw the exact volume of blood shown on the label. If a tube has lost all or part of its vacuum, it will fail to properly fill with blood. The expiration date should always be checked on the label. Improper storage, opening the tube, dropping the tube, pushing the needle too far into the tube prior to venipuncture, or the needle bevel coming partially out of the patient's skin during collection are all causes of underfilled tubes, or "short draws". This may adversely affect test results since the blood to additive or anticoagulant ratio is thrown off.
Additives and Anticoagulants:
Additives are substances put into the tube. Some are powder, some are liquid, some are sprayed into the tube, some are gel-based. They have one or more functions, such as:
- preventing clotting (anticoagulants)
- by chelating (binding) calcium OR
- by precipitating calcium
- in order to inhibit formation of thrombin needed to convert fibrinogen to fibrin in the coagulation process
- required for whole blood or plasma tests
- must be mixed gently immediately after collection to prevent microclot formation and hemolysis
- K2EDTA or K3EDTA (di-potassium or try-potassium ethylenediaminetetraacetic acid): lavender, purple or pink-top tubes
- K2 is powdered
- K3 is liquid
- Most are in spray-dried form to prevent dilution of the specimen
- Salt
- Chelating agent (binds calcium)
- Whole blood or plasma (when spun)
- citrates: blue-top tubes
- bind/chelate calcium
- sodium citrate the most common
- preserves coagulation factors but prevents coagulation
- require immediate, gently mixing
- require 9:1 ratio of blood to anticoagulation and filling of tube to 90%
- heparin: light green or dark green tubes
- prevents clotting by inhibiting thrombin formation
- ammonium heparin
- lithium heparin (light green)
- causes the least interference in chemistry testing and most widely used type (preferred)
- do not use to test for lithium
- causes the least interference in chemistry testing and most widely used type (preferred)
- sodium heparin (dark green)
- ammonia OK to test
- do not use to test for sodium
- use to test lithium
- ammonia OK to test
- results in plasma
- oxalates
- precipitate calcium
- potassium oxalate the most widely used type
- acid citrate dextrose (ACD)
- solution A
- solution B
- for DNA testing and HLA phenotypic and paternity
- binds calcium
- gives RBC's nutrients (dextrose) and maintains viability
- citrate phosphate dextrose (CPD)
- used in collecting units of blood for transfusion
- chelates calcium (citrate)
- stabilizes pH (phosphate)
- gives cells energy and life (dextrose)
- sodium polyanethol sulfonate (SPS)
- binds calcium
- used for blood culture collection
- reduces complement
- slows down phagocytosis
- reduces activity of antibiotics
- antiglycolytic agents: gray-top tubes (sodium fluoride)
- prevent glycolysis
- preserves glucose
- sodium fluoride (most common)
- preserves glucose for up to 3 days
- inhibits bacteria
- results in plasma
- preserving certain blood components
- separating cells from plasma upon centrifugation
- gel separators like thixotropic gel (inert, non reacting)
- synthetic
- density is between that of the cells and that of plasma or serum
- when centrifuged, gel changes in viscosity (thickness) and moves between cells and liquid, creating a barrier between them
- prevents cells from continuing to metabolize glucose
- gel separators like thixotropic gel (inert, non reacting)
- activating clotting to obtain serum after centrifugation
- enhances coagulation in tubes used to collect serum specimens
- provide more surface area for platelet activation
- glass silica particles
- help blood to clot within 15-30 minutes
- inert clays like Celite
- clotting factors like thrombin
- help blood clot within 5 min.
- Lavender Top
- K2EDTA (spray) anticoagulant
- Must be completely filled to the line
- Must be inverted 8x after collection to thoroughly mix
- CBC (complete blood count)
- CBC w/DIFF (with differentiation) (morphology can be done)
- Platelets (count, scatter, morphology)
- ESR (Sedimentation Rate)
- BNP (B-Type Natriuretic Peptide)
- Chelating agent (binds calcium)
- Produces less shrinking of RBCs and less increase in cell volume
- Pink Top
- K2EDTA
- Invert 8x
- Blood Bank (Type and Screen, ABO/Rh,)
- White Top
- K2EDTA
- Invert 8x
- Separator Gel
- PPT's
- Molecular Tests
- Myocardial Infarction Panel
- Ammonia (Ice Slushy, Protected from Light)
- PCR
- Light Blue
- Sodium Citrate (3.2% or 3.8%) anticoagulant
- Must be completely filled to line
- Ratio of blood to anticoagulant is critical (9:1) (4.5 mL of blood to 0.5 mL of sodium citrate)
- Invert 3-4x
- Centrifuge
- Plasma is used for coagulation tests (PTT, aPTT, TT, D-Dimer, Fibrinogen, Westergren ESR)
- If the patient has polycythemia or a Hct of >55%, the anticoagulant amount should be decreased to prevent the amount of citrate in the plasma, which would in turn interfere with coagulation tests/studies, so use 3.2%
- Always check for clot formation first before testing
- Black
- Buffered sodium citrate anticoagulant
- 4:1 ratio
- Invert 3-4x
- Westergren sedimentation rates
- Green
- Heparin with sodium, lithium (preferred, least interfering), or ammonium ion
- Inhibits thrombin
- Invert 8x
- Chemistry tests on whole blood or plasma
- NOT used in hematology (interferes with Wright's stain for CBC)
- Ionized calcium can be tested from this tube on whole blood or serum, depending upon the analyzer
- Full draw (2 mL) required
- Used for testing pH, blood gases, electrolytes, ionized calcium, BMP, CMP, renal panel, MG/PHOS, ammonia
- Light Green
- Lithium heparin
- Separation Gel (PST or SST)
- Plasma separation
- Invert 8x
- Chemistry tests (BMP, CMP, Potassium, Magnesium, Troponin, Procalcitonin, CKMB, CPK, BUN, etc...)
- Vitamin B6 (Ice)
- Liver Panel
- Glucose
- Electrolytes
- Creatinine
- Amylase
- Albumin
- Alkaline phosphatase
- Ammonia (ICE)
- ALT
- AST
- Bilirubin
- Lipase
- Troponin
- TSH
- Gray
- Contains anticoagulants + additives
- Preserves glucose
- Contains sodium fluoride, which maintains stability for 3 days
- Serum testing
- Invert 8x
- Blood alcohol level, lactic acid (LA)
- Gray Stopper for Urine Culture
- Contains potassium oxalate (Na2EDTA)
- Preservative for urine culture only
- NOT used for hematology tests
- Royal Blue
- Contains K2EDTA
- Used for toxicology testing
- Trace metals (lead)
- Nutrition tests
- Invert 8x
- Tan
- Trace metal lead testing
- K2EDTA
- Invert 8x
- Yellow
- Contains acid citrate dextrose (ACD)
- Used for cell studies, phenotyping, DNA, Paternity
- Sterile with SPS for microbiology cultures
- Invert 8x
- Light Blue/Black
- Contains sodium citrate
- Invert 8x
- Poly. gel
- Density gradient liquid
- Cell prep tubes (CPTs)
- Whole blood molecular testing
- Check for clots first before testing
- Red/Green
- Contains sodium heparin
- Poly. gel
- Density gradient liquid
- CPTs
- Invert 8x
- Whole blood molecular testing
- Hep. blood
- Yellow/Gray and Orange
- Thrombin
- Activates clots faster (within 5 minutes)
- STAT serum chemistry
- Chemistry tests on patients with anticoagulant therapy
- Invert 8x
- Orange
- Thrombin-based med. clotting agent
- Separation gel
- Invert 5x
- Rapid serum tubes (RSts)
- Clot within 5 minutes
- Centrifuge 10 min. @ high speed
- Serum tests
- Red/Gray and/or Gold (no additive): serum
- Needs to sit for 30 minutes first to clot prior to centrifugation
- Invert 5x
- Contains a clot activator (silica)
- Separation gel
- SSTs
- Polymer barrier gel (bottom of tube)
- Cells/Barrier/Serum
- Useful for most chemistry tests and some molecular tests
- Serum is used for some immunoassays
- NOT used in bloodbanking
- Red (no additive): serum
- Needs to sit for 60 minutes prior to centrifugation in order to clot first
- Invert 5x
- Silica clot activator
- Serum chemistry and serology tests (like serum pregnancy) and blood banking (serum and RBCs)
- No anticoagulants or additives
- Centrifugation yields serum as opposed to plasma
- Glass types don't need inverting
- Digoxin
- Acetaminophen
- Antibiotic levels
- Valproic Acid
- Cold Agglutinins
- Red/Light Gray and Clear
- Discard tubes
- No anticoagulants or additives or gel
- Coagulation studies with winged blood collection set
- Secondary sample collection tube
- No inversion needed
- Red/Yellow Tiger
- Urine chemistry and microscopy
- Clear
- Urine pregnancy
- Urine DRUG screen
- Gold
- T3
- T4
- TSHR
- HIV
- ALT
- AST
- BMP
- CMP
- Electrolytes
- Creatinine
- Albumin
- Amylase
- Alkaline phosphatase
- CPK
- Bilirubin
- Iron
- FT3
- FT4
- Hepatitis
- LDH
- Lipase
- Lipid Profile
- Osmolality
- RPR
- Serology
- Total Protein
Components of Blood:
The major (solid) components of blood are:
When you go to the doctor and they collect your blood, sometimes they spin down your blood to separate it into 3 different parts or layers that they can test for various things. This is performed by centrifuging your blood (spinning it down) at a high rate of speed (rounds per minute or rpms) in a centrifuge.
Centrifuged blood divides into three distinct layers:
-It is mostly water (up to 95%)
-It contains dissolved components, including proteins (albumin, fibrinogen, globulin), sodium, glucose, clotting factors, electrolytes, hormones, carbon dioxide
-Because it is intravascular fluid, it helps to maintain osmotic pressure that keeps everything in balance
-This is prepared by spinning or centrifuging the blood in an anticoagulant-coated tube (EDTA, which is the lavender/purple-top tube). This keeps the blood from clotting.
- Red Blood Cells (a)
- White Blood Cells (b, c, d)
- Platelets (the little tiny purple spheres between the red and white blood cells)
When you go to the doctor and they collect your blood, sometimes they spin down your blood to separate it into 3 different parts or layers that they can test for various things. This is performed by centrifuging your blood (spinning it down) at a high rate of speed (rounds per minute or rpms) in a centrifuge.
Centrifuged blood divides into three distinct layers:
- Packed red blood cells (bottom/this is referred to as the hematocrit)
- Buffy layer (middle/consists of white blood cells, platelets)
- Plasma (straw-colored, fluid portion of blood containing fibrinogen and clotting factors)
-It is mostly water (up to 95%)
-It contains dissolved components, including proteins (albumin, fibrinogen, globulin), sodium, glucose, clotting factors, electrolytes, hormones, carbon dioxide
-Because it is intravascular fluid, it helps to maintain osmotic pressure that keeps everything in balance
-This is prepared by spinning or centrifuging the blood in an anticoagulant-coated tube (EDTA, which is the lavender/purple-top tube). This keeps the blood from clotting.
Serum and Serum Separator Tubes (SST):
Serum is the fluid portion of the blood that DOES NOT contain the clotting factors. It contains all the proteins NOT used for coagulation/clotting. It DOES NOT contain the red or white blood cells or platelets. It is basically the blood plasma MINUS the fibrinogens. It is used for many tests in the clinical laboratory.
A serum separator tube (SST), gold or marbled tiger top Vacutainer tube, is used to separate the blood into serum and blood cells. The SST contains gel that moves between to separate the blood cells and serum during the centrifugation process. It also contains clot activator. Centrifugation and clot activator speed up the natural blood clotting process, which would otherwise take about an hour to occur if left on its own. The gel also contains particles that help the blood to clot quickly so that testing on the serum can begin right away, and has an intermediate density between the blood cells and blood plasma. Therefore, during the spinning process, the blood cells sink to the bottom of the tube and the gel moves between the blood cells and serum separating them into two entities. The gel prevents the blood cells and serum from remixing during the transportation process.
Coagulated blood is clotted blood that yields serum without fibrinogen, but some of the clotting factors remain.
A serum separator tube (SST), gold or marbled tiger top Vacutainer tube, is used to separate the blood into serum and blood cells. The SST contains gel that moves between to separate the blood cells and serum during the centrifugation process. It also contains clot activator. Centrifugation and clot activator speed up the natural blood clotting process, which would otherwise take about an hour to occur if left on its own. The gel also contains particles that help the blood to clot quickly so that testing on the serum can begin right away, and has an intermediate density between the blood cells and blood plasma. Therefore, during the spinning process, the blood cells sink to the bottom of the tube and the gel moves between the blood cells and serum separating them into two entities. The gel prevents the blood cells and serum from remixing during the transportation process.
Coagulated blood is clotted blood that yields serum without fibrinogen, but some of the clotting factors remain.
Serum: Icteric, Lipemic and Hemolytic
After centrifugation of blood into its components by a SST (serum separator tube), the serum may appear something other than clear. It is helpful to be able to recognize these differences because sometimes they can interfere with Chemistry tests.
Icterus (Icteric Specimens):
As seen in the images below, icterus or hyperbilirubenemia (increased bilirubin levels) ranges from 1+ to 4+. Normal, straw-colored serum can be seen on the far left (0). As levels of bilirubin are present or increase, the color of the serum ranges from light gold to amber to dark gold to brownish. This can indicate jaundice or a liver problem, which may range from a virus to alcoholism to cirrhosis to a fluke to a gallstone or hemolytic anemia. The following are tests that may be affected by an icteric sample:
Icterus (Icteric Specimens):
As seen in the images below, icterus or hyperbilirubenemia (increased bilirubin levels) ranges from 1+ to 4+. Normal, straw-colored serum can be seen on the far left (0). As levels of bilirubin are present or increase, the color of the serum ranges from light gold to amber to dark gold to brownish. This can indicate jaundice or a liver problem, which may range from a virus to alcoholism to cirrhosis to a fluke to a gallstone or hemolytic anemia. The following are tests that may be affected by an icteric sample:
- Mg++ (increased)
- Cholesterol (decreased)
- Triglycerides (decreased)
- Creatinine (decreased)
- Bile acids (decreased)
- Lipase (decreased)
- Total protein (decreased)
- Uric acid (decreased)
- GGT (decreased)
Hemolytic Specimens:
Hemolysis is a very common finding in laboratory specimens and is a frequent cause of specimen inadequacy and rejection. Hemolysis is when red blood cells rupture, releasing the hemoglobin pigment, causing the serum to appear pink to orange to red-orange to cherry red. Hemolysis may be intravascular (occur within the patient's veins) or extravascular (outside the veins, in between the cells, or in the specimen itself during centrifugation or mishandling of a specimen or during the phlebotomy blood collection process).
Hemolysis interferes with the spectrophotometric properties of many laboratory instruments and can cause results to be inaccurate. It can actually dilute the serum or plasma. Hemolysis may be 1+, 2+, 3+ or 4+. At 1+, depending upon the lab, some results might be released with a comment letting healthcare personnel be aware of slight hemolysis and to interpret the test with caution. At 2+ hemolysis, most labs will likely have a protocol to call the nurse or physician first and possibly dilute or rerun the sample or request a new sample. At 3+ hemolysis or higher, you should definitely call the nurse or physician, reject the sample, reorder a new one if they wish and ask for a recollect of a new sample. The following tests may be affected by moderate to heavy hemolysis:
Decreased Values:
Increased Values:
Lipemic Specimens (Lipemia):
In an individual with increased fats, cholesterol or triglycerides in the bloodstream, the serum or plasma components may appear lipemic, thick and cloudy or milky and turbid due to the presence of these excess fats. Tests that are especially affected include the electrolytes sodium (Na+) and potassium (K+). Hemolysis often occurs along with lipemia because lipemia greatly enhances rupture of red blood cells. The following tests are affected:
Decreased Values:
Increased Values:
Since lipemia is one of the most common interferences in clinical chemistry specimens, the sample can be centrifuged at high speed (10,000 rpm's/min) for 15 minutes or it can be ultrafuged.
Hemolysis is a very common finding in laboratory specimens and is a frequent cause of specimen inadequacy and rejection. Hemolysis is when red blood cells rupture, releasing the hemoglobin pigment, causing the serum to appear pink to orange to red-orange to cherry red. Hemolysis may be intravascular (occur within the patient's veins) or extravascular (outside the veins, in between the cells, or in the specimen itself during centrifugation or mishandling of a specimen or during the phlebotomy blood collection process).
Hemolysis interferes with the spectrophotometric properties of many laboratory instruments and can cause results to be inaccurate. It can actually dilute the serum or plasma. Hemolysis may be 1+, 2+, 3+ or 4+. At 1+, depending upon the lab, some results might be released with a comment letting healthcare personnel be aware of slight hemolysis and to interpret the test with caution. At 2+ hemolysis, most labs will likely have a protocol to call the nurse or physician first and possibly dilute or rerun the sample or request a new sample. At 3+ hemolysis or higher, you should definitely call the nurse or physician, reject the sample, reorder a new one if they wish and ask for a recollect of a new sample. The following tests may be affected by moderate to heavy hemolysis:
Decreased Values:
- Troponin
- Bilirubin
- Amylase
- Haptoglobin
- Bicarbonate
Increased Values:
- Potassium (K+)
- Magnesium (Mg+)
- Calcium (Ca++)
- Lactate dehydrogenase (LDH)
- Creatine Kinase (CK)
- AST
- ALT
- Total protein (TP)
- Iron (Fe)
- Phosphate
- Albumin
- Alkaline phosphatase (ALP)
Lipemic Specimens (Lipemia):
In an individual with increased fats, cholesterol or triglycerides in the bloodstream, the serum or plasma components may appear lipemic, thick and cloudy or milky and turbid due to the presence of these excess fats. Tests that are especially affected include the electrolytes sodium (Na+) and potassium (K+). Hemolysis often occurs along with lipemia because lipemia greatly enhances rupture of red blood cells. The following tests are affected:
Decreased Values:
- Sodium (Na+)
- Potassium (K+)
- Chloride (Cl-)
- Bicarbonate
- Lactate dehydrogenase (LDH)
Increased Values:
- Direct bilirubin
- Total bilirubin
- Magnesium (Mg++)
Since lipemia is one of the most common interferences in clinical chemistry specimens, the sample can be centrifuged at high speed (10,000 rpm's/min) for 15 minutes or it can be ultrafuged.
Carryover/Cross-Contamination:
Carryover or cross-contamination happens when additive is transferred from one tube to the next, or when the blood is contaminated with IV fluids. This is why proper order of the draw is so important, drawing blood from the right site on the patient, and being mindful of collection procedures. Errors that can cause specimen hemolysis or contamination include:
Prior to drawing a blue top for PTT, PTINR and aPTT, a few mLs of blood should be drawn into a nonadditive tube first (waste tube) to prevent contamination and tissue thromboplastin contamination.
- drawing blood from a hematoma or a vein with one
- failure to wipe away the first drop of capillary blood or alcohol residue
- forceful aspiration of blood during the syringe draw
- forcing blood from a syringe into an evacuated tube
- horizontal transfer of tubes
- mixing tubes too vigorously
- partial fill
- pulling back on plunger too quickly
- rough handling during transport
- squeezing the site during specimen collection
- leaving the tourniquet on too long
- wrong needle size during collection
- drawing blood through an IV valve
- failure to use a discard tube for the first volume of blood after turning of the IV infusion
- failure to turn off the IV infusion or to turn it off for the proper amount of time prior to drawing blood for testing
Prior to drawing a blue top for PTT, PTINR and aPTT, a few mLs of blood should be drawn into a nonadditive tube first (waste tube) to prevent contamination and tissue thromboplastin contamination.
Need to be on Ice Slurry:
- ACTH
- Acetone
- ACE
- Ammonia
- Lactic Acid (plus, check for clot first prior to running)
- Catecholamines
- Free fatty acids
- Gastrin
- Glucagon
- Homocysteine
- PTH
- pH/blood gas
- Pyruvate
- Renin
Refrigerate:
- Anything after 2 hours
- Methotrexate
- FK504 (tacrolimus)
- Cyclosporine
Heat 10 Minutes at 56 Degrees Celsius Water Bath For 10 Minutes Followed by Ice Slurry for 10 Minutes:
- Fractionated Alkaline Phosphtase (Heated)
Pretreat:
- FK504 Tacrolimus
- Cyclosporin
Filter:
- Free Phenytoin
- Free Valproic Acid
- Requested Post-Filtered Ionized Calciums (rare)
Protect From Light:
- Bilirubin samples
- Carotene
- Red cell folate
- Serum folate
- Vitamins B2, B6, B12, C
- Urine porphyrins
- Urine porphobilinogen
QNS:
Quantity not sufficient
Clotted
Hemolyzed
Clotted
Hemolyzed
Aliquots:
- Pour-off cups
- Transfer a portion of specimen into one or more labeled tubes
- Use disposable transfer pipettes, not pouring, to decrease risk of splashing, spraying, splattering, or aerosols
- Recap tube right away
Order of the Draw:
- Discard tube(s) first if needed if drawing from a line or near one
- If needed, blood culture or SPS yellow top sterile tube
- Light blue-top
- Serum tube with or without clot activator or with or without gel (red or gold)
- Heparin tube (light green and or dark green)
- EDTA (lavender and/or pink)
- Glycolytic inhibitor (gray)
Recap or Seal:
- for prevention of loss of CO2 and rises in pH
IV Catheter Line Contamination:
Many hospital inpatients have IV catheters for infusing fluids such as saline-dextrose (glucose) and medications. When at all possible, drawing blood from patients for laboratory testing should be accomplished by vascular draws rather than line draws in order to prevent possible contamination with glucose or sodium and to prevent disruption of the red blood cell mean corpuscular volume, which can affect chemistry and hematology tests in the laboratory.
For this reason, the goal is to collect venous blood from the opposite arm whenever possible to avoid contamination and possible elevation of the values of some of the chemistry tests. Additionally, since blood tends to pool in the periphery of the limb, collecting blood distal to the catheter should also be avoided. On the other hand, collection of fluids proximal to the line will cause them to be diluted by the infusion fluid, possibly lowering the values of some of the chemistry tests. When vascular access is limited due to hematoma, scar tissue, small or rolling veins, tattoos, or other reasons, sometimes there is no other choice but to draw from a line. Infusion fluids should be stopped for about 10-15 minutes prior to drawing from a line in order to reduce the chance for contamination, plus, the first draw of blood should be drawn into one to three discard tube(s) and discarded in case it is contaminated with glucose and/or sodium from the saline solution. This is considered a means of flushing the line. Contaminated fluids may cause an increase in glucose levels of at least 100 mg/dL. Electrolytes on this same specimen may be falsely decreased due to dilution of the specimen. Some references to look for with regards to possible IV contaminated specimens are as follows:
|
EDTA Contamination:
Suspected EDTA contamination occurs when blood is drawn from a line or from the same arm as a line and the phlebotomist forgets to draw a discard tube first or draws the order of the draw in the wrong order, resulting in carryover from the lavender-top tube into other tubes.
- K+ may be increased
- Ca++ may be affected (too low)
- Glucose may be increased
- Mg+ may be affected (too low)
- Fe may be affected
- AlkP (too low)
Urine Samples:
In Chemistry, urine is commonly tested to evaluate
Urine is either concentrated or dilute. It depends upon whether the individual is properly hydrated or dehydrated, medications they may be on, a possible UTI, kidney function, and other factors.
- kidney functions
- waste products excreted by the kidneys
- metabolites that build up in the urine, including drugs of abuse
- glucose, which may spill over into the urine of patients with diabetes
- protein, which may spill over into the urine of patients with diabetes
Urine is either concentrated or dilute. It depends upon whether the individual is properly hydrated or dehydrated, medications they may be on, a possible UTI, kidney function, and other factors.
Urine Samples for Clinical Chemistry:
Preservatives:
Preservatives in urine prevent the breakdown of analytes and aid in the prevention of microbial growth where urine cannot be tested right away. Urine needs to get to the laboratory ASAP and must be refrigerated within 2 hours if it is not tested immediately. The urine pH can also be adjusted to an acidic or basic level. Below are examples of urine preservatives:
- Potassium phosphate
- Benzoic acid
- Sodium bicarbonate
- Acetic acid
- Hydrochloric acid
- Boric acid
- Urines are kept for 7 days, with the exception of positive drug screen urines and body fluids, which are kept for 4 weeks, always refrigerated
Types of Urine Specimens/Priority:
- First Morning Sample:
- Concentrated urine from overnight buildup of metabolites
- Used for proteins or rare analytes
- Random:
- Any time
- Routine Screening
- Timed:
- 2-6 hours
- 24-Hour Urine:
- Need complete collection time in minutes (24 hours is 1440 minutes)
- Need patient weight
- Collected in a jug
- Aspirate (rare):
- a special technique used to collect urine from infants or young children if other methods are unsuccessful
- a special technique used to collect urine from infants or young children if other methods are unsuccessful
Other Fluids:
- Each lab has its own criteria for testing body fluids and what can be done in-house or what is sent out to a reference lab
- CSF: need to verify the tube #
- tests for meningitis
- tests for multiple sclerosis
- tests for cerebrovascular accident
- tests for meningitis
- Spin body fluids for testing
- Treat as STAT or ASAP
- Fluids Tested:
- Amniotic Fluid
- fetal health
- fetal health
- Synovial Fluid
- Pleural Fluid
- Peritoneal Fluid
- Pericardial Fluid
- Saliva
- drugs
- alcohol
- drugs
- Amniotic Fluid
- Transudates: leaking from blood vessels due to pressure differences, resulting in low in protein
- Exudates: inflammation or injury resulting in high protein
Sample Tube Priority (Read the Label):
- Crisis
- STAT (St/ST)
- ASAP
- Timed (Ti)
- Routine (Rt/Rou)
- Add-on (Ad/Add)
Total Parenteral Nutrition (TPN):
Total Parenteral Nutrition, or TPN, is intravascular (IV) gastrointestinal bypass feeding that may affect the serum/plasma of some patients. Because this may affect Chemistry tests, it is documented on the label, note or patient's chart. Typically this solution contains a high level of lipids and other nutrients that provide the patients who are comatose or who otherwise cannot physically eat and digest a balance of nutrients to sustain life.