Clinical guidelines

General specimen preparation

For general sample preparation, please follow the instructions stated in the respective profiles and single tests listing in our Services Guide. Also refer to Table 1a and 1b as a reference to ensure proper use of collection containers. 

Patient identification

Provide two identifiers for every patient for each sample tube. A minimum of two of the the following are required: surname and given name, plus one of the following: date of birth, NRIC/Passport No., etc. The samples cannot be processed if this information is not present.

Sample collection: Blood/Serum/Plasma

1. Ensure patient has correctly followed any preparations eg. fasting.
2. Patient should be resting and seated, ideally for 5 – 10 mins before sample collection.
3. Tourniquet should be tightened ideally for under 30 seconds or no longer that than 1 min.
4. If more than one type of sample tube is to be used, collect tubes according to Table 1a
5. Tubes must be thoroughly mixed by gently inverting (not shaking) the tubes.
6. If storage is required before sample collection, chill sample at the right temperature.
7. Keep LDH isoenzymes samples at room temperature.

1. Before collecting any blood specimen, the person administering phlebotomy should wash his/her hands, wear protective clothing and disposable gloves.
2. Sample containers should be carefully labelled with two unique identifiers.
3. It must be verified that the patient has been fasting, if fasting is a requirement for the requested tests.
4. Ensure that a sufficient number of tubes are prepared for the required test. Select an appropriate sized needle for the vein to be punctured.
5. The patient’s arm should be extended in a straight line at a 45° angle from the shoulder to the wrist.
6. The median cubital vein in the antecubital fossa is the preferred site for blood collection in adults.
7. Apply a tourniquet 3 to 4 inches above the intended puncture site to obstruct return of venous blood to the heart and to distend the veins. The tourniquet should not be left tightened for more than one minute, and the patient should not pump the fist while the tourniquet is in place. This is essential to avoid haemolysis of the sample and errors due to fluid, protein and electrolyte shifts in the occluded vein. It is especially important when taking blood for cholesterol testing.
8. The area around the intended puncture site must be cleaned with an alcohol swab, wiping in a circular motion from the site outwards. The site must be allowed to air-dry before sampling, as alcohol may cause haemolysis of the sample. If blood is being taken for alcohol testing, an alcohol swab must NOT be used; instead use an alcohol-free benzalkonium chloride solution. Once the skin has been cleaned, it should not be touched again until after the venepuncture has been completed.
9. Insert the needle into the vein, and take blood samples in the following order:
   1. Biochemistry tubes (clotted blood)
   2. FBC tubes (EDTA blood)
   3. Glucose tubes (fluoride blood)
   4. All tubes with additives (EDTA-lavender top, heparin-green top, and glucose-grey top, for example) must be completely filled.
10. When blood collection is complete, the tourniquet should be loosened, then the needle withdrawn from the vein. When the needle has been withdrawn, a dry gauze swab must be held firmly over the puncture site for a few minutes. A small plaster can then be placed over the site.
11. After sampling, needles should be disposed in an appropriate manner into a designated container.

• Unlabelled samples.
• Samples not accurately and properly identified.
• Use of incorrect container or collected improperly (use of non-sterile containers).
• Insufficient sample volume.
• Clotted sample.
• Use of expired collection media, tube or kit.
• Contaminated samples.
• Leaking / broken container.
• Suboptimal sample (too old to yield accurate results).

Random samples for microbiology should be collected in a sterile container. Hands must be thoroughly washed and dried before the sample is collected.

Collect a mid-stream sample and care should be taken that no part of the body touches the rim or interior of the container before, during or after collection. The lid should be securely fastened after collection. 

Timed samples (24-hr urine collection):

It is essential for interpretation of the results that urine collection is accurately timed.  A timed sample is to be collected as follows: 

1. Patient to empty his/her bladder and discard this urine.
2. The time must be noted; this is the time the collection is beginning.
3. All urine passed from that time until the end of the collection period must be collected in the container.
4. Inform the patient of the potential hazards associated with the preservative (if present) and advise them to handle the container with care.
5. During the collection period, keep the container in a cool, dry place. Refrigerate at 4-8 °C.

The sample requirements, including abstinence of certain foods and medications, vary from test to test. VMA testing has dietary restrictions eg. abstaining from vanilla, chocolate, coffee, bananas, citrus fruit, salt, aspirin and hypertensive drugs. As some preservatives can be harmful (particularly acids), patients should first void into a separate clean container and then immediately transfer the urine into the timed collection container.

24 hour/Overnight urine samples are not suitable for culture. If delay of delivery is expected, refrigerate sample before sending to laboratory. 

Microbiology samples

1. Refer to the test listing for the specific sample type and any associated collection instructions.
2. Proper collection is essential to avoid sample contamination.
3. Indicate appropriate clinical information and sample source/site on the request form.
4. Collect samples before the administration of antibiotics, if samples are collected after antibiotics has been consumers, this must be indicated on the sample request form.
5. Label the sample container clearly with 2 unique identifiers.
6. Send the sample to the laboratory promptly.

Liquid based cytology test

1. Collect adequate sampling from the cervix using a cytobrush.
2. Rinse the brush in the solution vial. Discard the brush. Do not leave brush inside the vial.
3. Tighten vial cap properly to prevent leakage.
4. Write patient’s name and ID on the label of the vial.
5. Provide clinical information and medical history on the request form.
6. Any unlabelled vials will be rejected.

Sequence of draw

Source: BD Order of Draw Chart

List of critical values of laboratory tests

Scheduled test guide (updated March 2026)