Clinical chemical test blood specimen refers to a certain amount of blood collected for completing one or more clinical chemical test items, including anticoagulation and non-anticoagulation.

Second, the adoption of blood samples.

(a) take the parts

1. Venous blood collection: the most widely used blood collection method. Commonly used veins are anterior elbow vein and dorsal wrist vein, while jugular vein and anterior fontanel vein are sometimes used in children and newborns.

2. Arterial blood sampling: mainly used for blood gas analysis. Common arteries are femoral artery, brachial artery, radial artery and umbilical artery.

3. Capillary blood collection: suitable for experiments or babies who only need trace blood. The common parts are earlobes and fingertips, and sometimes children's big toes and heels. The depth of the blood collection needle penetrating into the skin should be 2mm. 2.5mm), local blood should be no inflammation, edema, etc.

(2) Specimen type

Clinical chemical test blood samples are divided into serum, plasma and whole blood. There is no difference in most chemical components between serum and plasma, except that the former does not contain fibrinogen. Whole blood is used only when the composition of red blood cells is similar to that of plasma; Whole blood is used for blood gas analysis and hemoglobin electrophoresis, but not for general clinical chemical analysis.

3. Whole blood is regarded as serum or plasma.

Blood samples should be collected as soon as possible in order to naturally separate serum (plasma) from whole blood that comes into contact with blood cells. Generally, serum or plasma should be separated within 2 hours after blood collection. Whole blood treatment is divided into three stages: before centrifugation, after centrifugation, and each stage has specific requirements.

(1) Pre-centrifugation stage

That is, a period of time before the index books are collected and centrifuged.

1. Serum: Generally, samples should be allowed to agglutinate themselves before centrifugation, and blood clots should not be peeled off with a wooden stick. Usually, blood samples can be completely spontaneously agglutinated at room temperature (22 ~ 25℃) for 30 ~ 60 min. The agglutination reaction of refrigerated samples is slow; Adding coagulant will accelerate the agglutination (after the specimen is collected, it should be gently inverted and stirred for 5 ~ 10 times to ensure the function of coagulant).

2. Plasma: When a plasma sample is needed, a blood sample collection tube containing anticoagulant must be used, and the blood collection tube must be gently reversed and mixed for 5 ~ 10 times immediately after blood collection (to ensure the anticoagulant to play its role). Plasma can be separated after 5 ~ 10 minutes.

3. sample refrigeration: sample refrigeration can inhibit cell metabolism and stabilize some temperature-dependent components, but whole blood samples can not be refrigerated generally; The sample used to determine blood potassium should not be refrigerated for more than 2 hours. The detection of catecholamine, pH/ blood gas, ammonia, lactic acid, pyruvate, gastrin and thyroid hormone in blood requires freezing samples.

When the specimen needs to be refrigerated (2 ~ 8℃), it should be immediately put into ice or ice-water mixture (large ice is not allowed), and the specimen must be fully contacted with refrigerant to ensure that the refrigerant reaches the height of the specimen.

4. Metabolic inhibitors and preservatives: Some additives can inhibit cell metabolism and prevent the change of analyte concentration when blood samples are stored. When measuring blood sugar, if sodium fluoride is added to blood, glucose can be stabilized for 24 hours at 22 ~ 25℃ and for 48 hours at 2 ~ 8℃ without separating blood cells. However, due to the high hematocrit of newborns and children, it is difficult to control the glycolysis of cells with sodium fluoride. Formaldehyde-potassium oxalate anticoagulant preservative is not suitable for blood sugar determination; Sodium fluoride-thymol mixture is not suitable for enzymatic determination because it can inhibit the activity of enzyme.

5. Specimen collection location: (1) Specimen should be sent to the laboratory as soon as possible after collection, especially when the temperature in the collection area exceeds 22℃; (2) After blood sample collection, the blood vessel must be plugged, and the nozzle should be placed vertically upward, so as to reduce the vibration of the contents in the tube, promote complete solidification, and prevent evaporation, pollution and splashing of the sample. (3) The collected blood samples should be treated gently to prevent hemolysis caused by the swing of the sample tube; Hemolysis will affect the determination results. The items that seriously affect (increase achievements) are: lactate dehydrogenase, serum aspartate aminotransferase, serum potassium and hemoglobin; The items that have a significant impact are: serum iron (? ), serum alanine aminotransferase (? ) and serum thyroxine (? ); Slightly affected (increased) are: total protein, albumin, serum phosphorus, serum magnesium, serum calcium and acid phosphatase; (4) Exposure of photosensitive analytes to artificial light or sunlight (ultraviolet rays) should be avoided. For example, VA, VB6, -When determining carotene, porphyrin, bilirubin, etc. The specimen tube should be protected by aluminum foil or similar substance.

6. Specimen transportation: Whole blood samples should be transported from the blood collection point to the laboratory as soon as possible. If the transportation distance is long, especially because the stability of the analyte is affected, serum or plasma can be separated at the blood collection point and sent to the laboratory if necessary; Attention should be paid to packaging, temperature requirements and treatment methods. The stability of samples during transportation to ensure the stability of analytical components; During transportation, the sample tube should be kept closed and placed vertically upward.

7. Laboratory specimen acceptance and centrifugation preparation: (1) Keep specimen acceptance records (check the list carefully during inspection, carefully record relevant information, and sign and register the specimen acceptance and processing); (2) Accepted specimens should be classified and prepared for centrifugation; (3) After the laboratory accepts the specimen, it should still keep the specimen tube sealed, with the nozzle facing upwards and placed vertically. After the plug is removed, the loss of CO2 in blood will lead to the increase of pH value, the decrease of ionized calcium and acid phosphatase, especially the change of pH value will affect the accuracy of some test results. (4) The agglutination time of the specimen should be sufficient; Blood samples containing anticoagulants can be centrifuged immediately; Samples with coagulants can be centrifuged at the earliest 5 ~ 15 min after blood collection; Anticoagulant whole blood samples (when determining zinc, lithium, protoporphyrin, etc. ) may not be centrifuged; (5) Cold storage (2 ~ 8℃) specimens should be kept at this temperature until they are ready for centrifugation. It is recommended to use a temperature-controlled centrifuge; (6) Before centrifugation, it is not recommended to peel off the clots attached to the test tube wall and plug with a small wooden stick or similar equipment. Artificial peeling can induce hemolysis. If you need to expose the test tube wall or pull out the plug, you must pay great attention to it, and the action must be gentle.

(2) Centrifugation stage

That is, the indicator has been placed in the centrifuge for some time.

1. Centrifugal time and relative centrifugal force (RCF): When blood samples are centrifuged in clinical chemical analysis, RCF (1000 ~ 1200)? G, the centrifugation time is 5 ~ 65438±00min.

2. Temperature-controlled centrifugation: The heat generated in the centrifugation process is not conducive to the stability of analytes, and temperature-controlled centrifuges must be used when blood samples are centrifuged for clinical chemical analysis. Some temperature-dependent analytes (such as adrenocorticotropic hormone, cyclic adenosine monophosphate, catecholamine, etc. ) should be separated at 4℃; For analytes without special temperature requirements, the centrifugation temperature should be set at 20℃ ~ 22℃; When the temperature is lower than 65438 05℃, the measured value of blood potassium can be artificially increased; Samples transported in cold storage must be centrifuged at the required temperature.

3. Centrifuge again: it is best to centrifuge the specimen once. If it needs to be centrifuged again, the time interval from the last centrifugation should be very short; Blood samples containing separated substances shall not be centrifuged again.

(3) Post-centrifugation stage

Refers to the period of time after centrifugation before taking out a certain amount of serum or plasma for detection.

1. The separation of serum or plasma from blood cells and blood clots should be completed as soon as possible (within 2 hours) after blood collection.

2. Storage of separated serum or plasma: The room temperature of the laboratory and the storage temperature and time of serum or plasma are important parameters for the stability of analytes and the accuracy of determination results. (1) Serum or plasma should not be stored at 22℃ ~ 25℃ for more than 8 hours; (2) If the experiment cannot be completed within 8 hours, the serum or plasma should be kept at 2℃ ~ 8℃; (3) The experimental items that cannot be completed within 48h, or the separated serum or plasma that needs to be kept for more than 48h, should be kept at -20℃; (4) Specimens should not be frozen and thawed repeatedly (only once), and should not be kept in a frost-free refrigerator (which may cause temperature changes of specimens); (5) The serum on the gel (gel barrier) after centrifugation can be stored for 2 ~ 5 days (it is also reported that it can be stored for 24 hours at 4℃), but the integrity of the gel must be ensured; However, when non-gel separation substances are used, serum or plasma must be removed immediately after centrifugation. (6) Serum or plasma must be kept in a closed test tube.

Four, serum or plasma separation substances

Refers to substances that separate serum or plasma from whole blood, including gel substances and non-gel substances.

(1) gel substance

Is an inert gel substance with specific viscosity and specific gravity (specific gravity between serum or plasma and clot), as (1000 ~ 1 100)? G RCF centrifugation 10 minute can form an impermeable gel barrier between serum or plasma and blood clots, thus separating blood cells and blood clots contacted with serum or plasma.

(2) Non-gel substance

It consists of beads, disks, filters, fiber plugs and other inert substances (glass, plastic, fiber, felt, etc.). ). With a specific gravity between serum or plasma and clot, gently add it into blood vessels, and use (1000 ~ 1 100)? When RCF g is centrifuged 10 minute, it can move between serum or plasma and blood cells and clots through blood, forming an interface, so that serum or plasma can be separated.

(3) A complete gel tube system

The system consists of vacuum blood collection tube (silicified plastic tube), which contains inert gel substance, coagulant or anticoagulant. Note that the product must have the corresponding performance certificate and validity period, and must be used correctly within its validity period.