Biological samples

Health Care

Samples for antibody research (Serodiagnostics, complement, autoantibodies, agglutinins, etc.) are in a dry tube.
Hematology, levies for NFS-VS are EDTA.
Samples for hemostasis tests are done on citrated tube. The samples for study of hemostasis must always be done according to strict rules detailed below.
In biochemistry, serum assays on are from levies on dry tube assays on plasma are obviously on anticoagulant (heparin, EDTA or oxalate). When a given anticoagulant is incompatible with the most widely used assay, this interference is reported as “heparin Sample, (…) are not suitable.”
Many assays can be either serum or plasma based on the method selected by the laboratory. In this case it says “Levy dry tube or pipe heparin.”
In the vast majority of cases, estimate plasma or serum does not influence the results. Among the assays presented in this book, one gives different results depending on whether it is done on plasma or serum, is that of glucose. The values ​​(different) serum and plasma glucose levels are noted under normal values.

Blood sampling for hemostasis test:

It is essential to observe the following precautions:
• preferably fasting patient;
• deduct from the opposite arm to a heparin infusion;
• unless absolutely necessary not to take on the catheter;
• if other tests are required, take the tube to study hemostasis last using the flow of the first milliliters of blood for further analysis;
• collect blood in citrate – the concentration of 3.2% sodium citrate or citrate Volume nine volumes of blood – or SDAC tube (in the follow-up treatment with heparin unfractionated). Any other anticoagulant is prohibited;
• strictly respect the volume of blood to be taken as indicated on the tube provided by the laboratory;
• Use silicone glass tubes;
• Do not leave the tourniquet in place more than 1 min (recommendation GEHT or study group on hemostasis and thrombosis);
• homogenising the blood and anticoagulant by eight to ten successive reversals;
• send to the laboratory within one hour of collection.

Arterial sampling for analysis of blood gases:

Blood is drawn by puncture of the radial artery after Allen test, which involves compressing both arteries, radial and ulnar to empty the hand of his blood. When it has turned white, the ulnar artery is released. If the hand is re-colors, the puncture is allowed because it shows that if the radial artery lesion during or after the gesture, the ulnar artery would take over.
Sampling strictly anaerobic (with the exclusion of air) without withers in a special disposable syringe heparin and bite the piston spontaneously rises under the influence of blood pressure.
Puncture obliquely at 45 °, the tip of the needle facing the arterial flow until the appearance of red blood in the syringe; 3 ml of blood are sufficient.
After puncture compress the artery for 5 min with an antiseptic impregnated dressing.
Any air bubbles must be expelled immediately to prevent changes in the oxygen partial pressure.
The puncture can also be done in the femoral or brachial artery.
At the often feared arterial puncture patients it is possible to prefer, an ultrafine needle aspiration for micromethod (100 uL enough) or a capillary blood sampling “arterialized” ear after cutaneous vasodilation by means of a special ointment applied for 10 min.
Determination of blood gases within 15 min after collection.

Blood samples for blood culture:

After aseptic technique of sampling site (70% alcohol more iodinated) for 1 to 2 minutes (follow this contact time), take by venipuncture using a single-use device.
Collect enough blood: 5-10 mL per vial in adults, 1-2 ml for children.
Avoid drawing blood from a catheter: high risk of contamination.
If the patient is treated with antibiotics, preferably use vials containing substances (resins, activated carbon) having a neutralizing effect on antibiotics.
Inoculate blood culture bottles after disinfection of the cap (70% alcohol iodinated allowed to dry). Two bottles of blood culture: one anaerobic and one aerobic (let filtered air).
Send as quickly as possible at room temperature laboratory. In the laboratory the bottles must be placed in an oven at 37 ° C immediately.
Notify the laboratory of a possible antibiotic.
Indicate the date, time, sampling site and the patient’s temperature.

Urine collection 24 h:

This type of collection is to be preferred to a split collection (nocturnal urine or urine collected over a fixed time: 2 or 4 or 8 h) whenever the elimination of dosed product (eg creatinine) is not constant over the nycthémère.
The empty his bladder patient to the toilet at a specific time (8 am for example); the corresponding urine is discarded.
All urine from all urination are then
gathered overnight at the same time, in a clean, sterile container. The last urination is collected.
Shake the jar (to mix the urine) before taking a sample for assay.
The most common mistakes are the conservation of the first urination, forgetfulness of urination, lack of collection during urination associated with defecation.

Assay of urinary creatinine

The assay of urinary creatinine ensures that the urine collection of 24 ha been total. Indeed, creatinine is a constant for a given individual, which is a function of their muscle mass. If creatinine is lower than they would the weight and size, is that the urine collection is incomplete.

Typical values:

• In men:
1100 2 000 mg / 24 h (10 to 18 mmol / 24 h)
20-26 mg / kg / 24 h (220 mol / kg / 24 h)
• For women:
800-1 350 mg / 24 hours (7 to 12 mmol / 24 h)
14-22 mg / kg / 24 h (177 mol / kg / 24 h)
All urine collection with creatinine deviates from these norms must be rejected regardless of the intended dosage: creatinine clearance, hormone dosage, calcium and phosphate levels, etc.

Acidification of urine:

Acidification of urine is essential if 5HIA dosage, oxalic acid, catecholamines, serotonin.
Prepare a jar containing 15 mL of HCl and 15 mL of water.
Acid and water should be placed in the jar before, not after, the collection or the results will be reduced.
Explain to the patient that the jar contains hydrochloric acid.
Then proceed as usual for a collection of 24-h urine.

Stool sample:

See Stool culture and parasitological examination of stools.

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