Collection and preservation of specimens
Common specimens for clinical testing generally include blood (referred to as blood, venous blood), urine, feces, cerebrospinal fluid, pleural and ascites fluid, prostate fluid, semen, vaginal secretions, etc. These specimens have certain requirements for collection time, method, and preservation.
1. Blood specimens Some physiological factors, such as smoking, eating, exercise, mood swings, pregnancy, posture, etc., can affect the changes of certain components in the blood, and some even have day and night changes. Therefore, the collection of blood specimens should avoid the interference of physiological factors as much as possible, and the conditions should be consistent. If this cannot be avoided, the factors should be noted on the specimens.
1. Peripheral blood Generally, blood is collected from the inside of the left ring finger. There should be no frostbite, inflammation, edema, or damage in this area. If the part does not meet the requirements, replace it with other finger parts. For patients with burns, blood can be collected from the entire skin. Because some blood routine tests (such as white blood cell count, classification, etc.) are subject to physiological factors, the fluctuations are too large, so the conditions should be as consistent as possible when comparing. Involving in-body test and blood coagulation function test items (such as platelet count, bleeding time or coagulation time, etc.), we must pay attention to understand whether the patient has used anticoagulation, procoagulant drugs in order to reduce or avoid the influence of interference factors.
2. Venous blood In addition to the various hemostasis and thrombosis tests involving anti-coagulation venous blood plasma, most of the current testing projects can directly use venous blood serum for analysis. In the serum test items, some (such as blood sugar, blood lipids, etc.) are greatly affected by diet and day and night factors, generally fasting blood samples in the morning are appropriate; some decay faster in the blood (serum enzyme activity measurement such as ACP activity, etc.), The storage activity of 0 ~ 4 ℃ is also weakened. The detection of these items must be timely and rapid; some (such as creatine kinase, etc.) are greatly affected by sports and other factors. It is also very important to avoid the occurrence of hemolysis when drawing blood, especially involving the determination of blood potassium and LDH.
2. Urine specimens As with blood specimens, urine specimens are also greatly affected by factors such as diet, exercise, and the amount of drugs, especially diet. Therefore, in general, morning urine is better than random urine. Morning urine refers to the first urine sample after waking up in the morning, which is more concentrated and acidified, and has relatively concentrated constituents (such as blood cells, epithelial cells, and tubular) that are easy to observe. Random urine is a random urine, which is convenient to take, but it is more affected by diet, exercise, and drugs. It is prone to false positive and false negative results, such as dietary proteinuria, dietary diabetes, and vitamin C interference occult blood results. Postprandial urine (patient urine collected 2 hours after lunch) is suitable for the detection of urine sugar, urine protein and urinary bilegen. Urine specimens at this time can increase the sensitivity of the test and detect milder lesions. The 12-hour urine cell count is the Addis count (all urine is taken from the bladder until 8 am the next day after emptying the bladder). Due to the longer time, the bacteria are prone to multiply and the preservative formaldehyde must be added. Quantification of chemicals in 24-hour urine (all urine taken from the bladder after emptying at 8 am on the first day to 8 am the next day), including protein, sugar, urine 17-keto, 17-hydroxysteroids, catecholamines, Ca2 +, etc., to detect different substances and choose different preservatives for preservation. The mid-clean urine is mostly used for urinary bacterial culture, which requires sterility. After washing the vulva, leave the specimen. The collection of all urine specimens should be sufficient, at least 12 ml, preferably 50 ml, all urine must be collected regularly, female patients should avoid vaginal secretions, menstrual contamination of urine specimens.
3. Fecal specimens The detection of fecal specimens has an important reference value for judging the diseases of digestive system. When collecting, it is required to use clean bamboo sticks to select feces containing abnormal pathological components such as mucus, pus and blood. Feces with no abnormal appearance must be collected from the surface, deep and multiple ends of the feces. When looking for parasites and counting eggs, collect feces for 24 hours. The dysentery amoeba trophozoite should be checked immediately after defecation, and the material should be taken from the place with pus blood and softness, and kept warm for inspection. When examining the eggs of Schistosoma japonicum, the mucus and pus blood should be taken. At least 30g of feces should be kept when the larvae are hatched, and they must be processed as soon as possible. Examination of pinworm eggs must be carried out with a transparent film swab from the folds around the anus at 12 pm or early in the morning before defecation and microscopic examination immediately. Occult blood test (chemical method), fasting meat and food containing animal blood and iron, vitamin C, etc. 3 days before the test. All stool samples should be checked within 1 hour after collection to prevent damage to digestive enzymes and pH.
4. Cerebrospinal fluid specimens CSF specimens are sent for inspection immediately after being collected. If left for too long, it will affect the test results: such as cell degeneration and destruction, resulting in inaccurate counting and classification; some chemical substances such as glucose will reduce the content of decomposition; bacteria autolysis affects bacteria Detection rate. After the cerebrospinal fluid is drawn, three sterile tubes are generally divided, the first tube is used for bacterial culture, the second tube is used for chemical analysis and immunological examination, and the third tube is used for general traits and microscopic examination. The order of the three tubes should not be reversed. Due to the difficulty of specimen collection, attention should be paid to safety during all inspection and testing procedures.
5. Thoracic and ascites specimens As with cerebrospinal fluid specimens, pay attention to the safety of the specimens after collection and promptly send them for examination. Generally, it is divided into three tubes, one tube for routine cytology examination, one tube for biochemical examination, and one tube for bacterial culture, and the sequence should be the same as cerebrospinal fluid.
6. Prostate fluid specimens Prostate fluid specimens are collected after prostate massage. When the amount of fluid is small, they are directly dropped on the glass slide for timely inspection. Care must be taken to prevent the specimens from drying out. If you can't massage the prostate fluid, you can check the urine sediment after massage.
7. Semen specimens Semen specimens should be abstinent for 3-7 days before collection. After draining urine, masturbation or other methods can be used to drain the semen directly into a clean container, keep warm and send it for inspection in time. Due to the large variability in sperm production during the day, it should generally be checked 2 to 3 times (each interval is 1 to 2 weeks) before diagnosis.
8. Specimens of vaginal secretions Sex, vaginal baths, vaginal examinations, vaginal lavage, and local application of drugs should be prohibited 24 hours before collection of vaginal specimens. The equipment used for sampling should be clean. Generally, a cotton swab moistened with saline is taken from the deep vagina or the back of the vaginal fornix, the cervical canal, etc., and a saline smear is made to observe the vaginal secretion specimens. The menstrual women should not check the vaginal secretion specimens.
