Sample Collection and Preparation of Sample in a Medical Laboratory

 

SAMPLE COLLECTING AND PREPARATION OF SAMPLE AND PATIENT

                                                                                                                   

Laboratory request form, specimen bottles and containers

This section deals with the information that is required to be documented on the laboratory request form and the specimen bottle or container, prior to the analyses of samples. The laboratory has a number of different request forms. These are used for different laboratory analyses as outlined below. It is important that the correct form is supplies for a particular test.

 

(Name of the laboratory)
Ordering physician		Specimen details
Name-	Signature-	Type of specimen-
Phone number-	Date-	Site of specimen-
Patient Details
Name-	Age-	Collection date and time-
Phone number-	Gender        Male
	Female	Test requisition
Address-	Clinical history -	1
		2
		3
		4
		5

 

 Specimen collecting containers (Collecting tubes for phlebotomy)

 

Red top
bnADDITIVE	non
Mode of action	Blood clots and the serum is separated by centrifugation
Users	Chemistries, Immunology and serology, blood bank

 

Green top
ADDITIVE	K3EDTA
Mode of action	Forms calcium salts to remove calcium.
Uses	Hematology (CBC) and blood bank; requires full draw- invert 8 times to prevent clotting and platelet clumping

 

Orange top
ADDITIVE	Potassium fluoride and sodium EDTA
Mode of action	Ant glycolytic agent preserves glucose up to 5 days.
uses	Glucoses, requires full draw

 

Pink top
ADDITIVE	Sodium citrate
Mode of action	Forms calcium salts to remove calcium
uses	Coagulation test (prothombing time). Full draw required.

 

PATIENT PREPARATION

The quality of results from laboratory testing depends greatly on the proper collection and handling of the specimen submitted for analysis.

Blood collection procedure

Venipuncture

1.         1. Site preparation at early morning

 

a) Cleaning of the collection site

                   • A clean surface including two chairs (one for the phlebotornist and the

                   • A hand wash basin with soap, running water and paper towels;

b) Use of personal protective clothing and additional protective equipment

c) Wash your hands before wearing the gloves

d) Have all blood collecting equipment ready and available

 

2.        2. Procedure for drawing blood

• Identify the patient by asking patient's name, age and requested test.
• Assess the patient's physical disposition (i.e. diet, exercise, stress, basal state).
• Check the requisition form for requested tests, patient information, and requirements
• Select a suitable site for venipuncture.
• Although the larger and fuller median cubical and cephalic veins of the arm are used frequently, the basilica vein on the dorsum of the arm or dorsal hand veins are also acceptable Venipuncture. Foot veins are a last resort because of the higher probability of complication

    3.Certain areas are to be avoided when choosing a site:

                • Extensive scars from burns and surgery - it is difficult to puncture the scar tissue

               • In case of mastectomy, the vein should be selected as indicated below as test results   may                         affected because of lymphedema.

 

   4. Prepare the equipment, the patient and the puncture site.

Equipment

• ·     Collection Tubes - The tubes are designed to fill with a predetermined volume of blood.

                    The plastic stoppers are color coded according to the additive that the tube container   and various sizes are available. Blood should never be poured from one tube to another can have different additives or coatings

•     Needles - The gauge number indicates the bore size: the larger the gauge number, the smaller the needle bore. Needles are available for use with a syringe, single draw or butterfly system.
• ·        Tourniquet - Wipe off with alcohol and replace frequently
• ·        Alcohol Wipes -70% isopropyl alcohol.
• ·        Povidone-iodine wipes/swabs - Used if blood culture is to be drawn.
• ·        Wool sponges - for application on the site from which the needle is withdrawn.
• ·        Adhesive bandages/tape-protects the venipuncture site after collection
• ·       Needle disposal unit - needles should NEVER be broken, bent, or recapped. Needles should be placed in a proper disposal unit IMMEDIATELY after their use.
• ·        Gloves can be made of latex, rubber, vinyl, etc.: worn to protect the patient and the phlebotomist.
• ·         Syringes - available in various volumes.

 

     5. Perform the venipuncture.

 

• •       Approach the patient in a friendly, calm manner. Provide for their comfort as much as possible, and gain the patient's cooperation.
• ·        Identify the patient correctly.
• •       Properly prepare labels, indicating the test(s) ordered.
• ·        Verify the patient's condition. Fasting, dietary restrictions, medications, timing, latex allergy and medical treatment are all of concern and should be noted on the lab requisition if there is any problem.
• ·        Position the patient. The patient should sit in a chair, lie down or sit up in bed. Hyperextend the patient's arm.
• •       Apply the tourniquet 3-4 inches above the selected puncture site. Do not place too tightly or leave on more than 2 minutes (and no more than a minute to avoid increasing risk for hernoconcentration). Wait 2 minutes before reapplying the tourniquet.
• ·        The patient should make a fist without pumping the hand.
• ·        Select the venipuncture site.
• ·        Prepare the patient's arm using an alcohol prep. Cleanse in a circular fashion, beginning at the site and working outward. Allow to air dry.

        

6. Collect the sample in the appropriate container. Order of draw

 

• •       Blood culture bottle
• •       Tube with 3.2% sodium citrate (Coagulation tube)
• •       Gel separator tubes with clot activator
• •       Serum separator tubes (Red top)
• •       Heparin tube with dark green top
• •       EDTA tube
• •       Tube with sodium fluoride and potassium oxalate

 

  7. Label the collection tubes at the bedside or drawing area.

• A properly labelled sample is essential so that the results of the test match the patient. The key elements in labelling are:
• ·        Patient's name.
• ·        Auto generated number.
• ·        Both of the above MUST match the same on the requisition form
• ·        Requested test(s)
• ·        Promptly send the specimens with the requisition to the laboratory.

Microbiology

 

Ensure the following information is fixed to each specimen container:

• Patient's first and last name
•  Auto-generated patient number
•  Source and type of specimen
• Date and time of collection

Multiple specimens requiring individual diagnosis should be placed in separate containers to be accessioned separately. If specimens are not labelled, or are mislabeled, a repeat Specimen may have to be collected resulting in a delay in processing. Exceptions will be made when invasive procedures are required for the specimen collection.

 

Urine Specimens

All urine specimens received in the laboratory must have, at a minimum, the following information fixed to the container (not lid): patient's first and last name, Auto-generated patient number and date and time of collection. 24 h or other timed collection must have in addition to the above: start and stop dates and times of collection. Deliver urine specimens to the laboratory as soon as possible after collection to maintain cellular and chemical stability. Some specimens require special or immediate handling after collection.