Introduction to Clinical Biochemistry to Specimen Collection

Clinical biochemistry is an area that concerned with biochemical changes in the body such as imbalances in the composition of blood, stool, cerebral spinal fluid (CSF) and urine. Determine the contents of the abnormal sample by testing it in the laboratories. The result can aid doctors and scientists make an indication or diagnosis if an organ in a normal condition.

Discussion:

1) There are few types of samples can be collected for the diagnostic purpose. The most common samples that can be collected are blood, urine, stool, and CSF. First of all, the blood sample which includes serum and plasma can be obtained from the patient through phlebotomy. Phlebotomy is a process of blood drawing or introduces a fluid into a body by piercing the vein and the process of piercing the vein known as venipuncture.

2) The procedures of phlebotomy include:

I. Position the patient in a proper and comfortable way. Then, ask the patient to hyperextend his or her arm.

II. Apply the tourniquet three to four inches above the puncture site. But, do not place the tourniquet too tightly or too long (not more than two minutes) to prevent haemoconcentration from happening.

III. Request the patient to make a fist without pumping the hand.

IV. Select the suitable venipuncture site. The available puncture site for venipuncture is the Median cubital vein, Cephalic vein, and Basilic vein.

V. Clean the patient's arm by using alcohol swab and allow it to air dry before puncture.

VI.Grasp the patient's arm and palpate or feel for the vein.

VII. The needle should insert through the skin into the vein in the form of 15 to 30-degree angle.

VIII. Filling the blood into the vacuum blood collection tubes and remove the tourniquet during the filling of the last tube.

IX. Remove the needle from the patient's arm carefully and immediately press down on the gauze once the needle is removed from the arm. Adequate pressure is required to press down to avoid the formation of a hematoma.

X. Dispose of the contaminated materials in the designated containers (shark bin).

XI.Mix and label all the blood filling tubes once finish filling the tubes.

3) For the size of needles that suitable for venipuncture are usually needles that range from 21 to 25 gauge. The smaller the needles gauze, the larger the diameter of the needle pore. Thus, The 21 gauze needles considered as the standard venipuncture needle for patients with normal veins and used primarily for large antecubital veins. 23 gauze needles usually for smaller antecubital, medium size forearm, veins of hand and foot while the 25 gauze commonly use to collect blood from tiny veins of premature neonates and infants. The 25 gauze needles rarely use in adults except for hand veins of the adults. The sample collected by using this size needles tend to be haemolysed than others.

4)The available size of the syringe is 1,3,5,10, 15 and 20 milliliter (ml). The size one and three ml is the most typical type of syringe that used for venipuncture.

5) Besides that, when a small amount of blood is required, capillary puncture which also called a finger stick or heel stick test can be carried out. This can be carried out by poking the skin with a lancet (a sharp needle) and collecting the blood drop onto a slide, test strip or capillary tube. The best site for capillary puncture is the center of the third (middle) finger pad, or fourth (ring) finger of the hand while for the heel stick capillary, foot lateral or medial plantar surface will be suitable.

6) The capillary tube or called as hematocrit tube for the blood collection is available in blue, red and green color. The blue color capillary tube does not have any anticoagulant, red color capillary tube consists of sodium heparin while green color capillary tube contains ammonium heparin. After collecting blood into the tube, the capillary tube or hematocrit have to undergo centrifuge in order to get hematocrit value

7)When the capillary tube used to collect serum bilirubin which is sensitive to light, it has to use clay or plasticine to block the opening of the tube and centrifuge it in a dark room to avoid false result occur.

8) Furthermore, urine is also the sample that can collect for diagnosis purpose. A urine sample can be collected in the variety of ways according to the type of specimen required. The most common three type of urine specimen is 24 hours urine, mid-stream urine and fresh urine.

9) The 24 hours urine sample is used to determine the number of solutes in the urine, for example like proteins to prevent the solute diurnal variation which might affect the result. The patient has to note the time of first and last void of the urine sample. All the samples have to collect in a sterile, large, opaque container that capable of holding four liters of the sample until 24 hours are completed. 24 hours urine specimen are used to measure the amount of creatinine, urobilinogen, protein, and calcium.

10) Next, the mid-stream urine (MSU) also known as clean catch sample. This method provides the cleaner or less contaminated sample than the random sample for microscopic analysis. It must only collect the center part of urine stream but not first and last part. It also has to use a sterile container to collect the sample. This is because MSU mostly for microbiological culture and antibiotic susceptibility testing so the presence of bacteria or normal flora on the genital part may cause contamination of the sample and lead to a false result.

11) Fresh urine sample also called as a random sample. This type of sample can collect at any time and without any precaution into a small (at least 50ml) yellow cap bottle. This type of sample mostly for the screening test such as drug abuse analysis. However, this type of sample is not considered as the best choice of the sample due to its potential of diluting sample during sample collection.

12) Moreover, a stool is one of the important samples for parasite and microbiology study. Procedures to collect stool sample are placing the potty in the toilet or spread clean newspaper over the toilet rim to catch the stool. When collecting the stool, the patient has to use the spatula that comes with the container and make sure the sample does not touch the inside of the toilet to avoid contamination. If there is no spatula been provided, the patient may use applicator stick instead. The suitable amount of stool sample will be around a third of the container. The most common container for stool collection is yellow cap cup.

13) Cerebral spinal fluid (CSF) is the fluid that surrounds the brain and spinal cord. CSF is a very precious sample due to it only can obtain a very small amount at one time and the process of obtaining it is extremely painful. This painful process carries out on the fully awake patient by experienced clinicians through lumbar puncture. Patient has to sit straight and then injected a numbing medication into the back through the skin. At the hip bones level, a thin needle is inserted into the back, between the spine bones to get the spinal fluid. About two to three tablespoons of CSF are required to collect into a sterile tube for testing purpose.

14) Every sample must have a proper label for the specimen identification. Mislabelled or unlabelled sample can result in patient received wrong treatment or do not get the right treatment that they need and cause irreversible consequences. The sample must have the specific identifiers of the patient such as patient’s full name, date of birth, unique identifying number (medical record number or barcode), time and date of collection, type of specimen, the test required and so on.

The common sample that required for the diagnostic test is blood, urine, stool and cerebral spinal fluid. Each of them has different collection method and container to place the sample. Furthermore, a proper sample labeling is very important for specimen identification.