Haematology

Introduction

Haematology Laboratory offers a comprehensive range of routine and specialised haematological investigations. The laboratory also offers Routine Urine Sediment Microscopy and molecular testing for diagnosis of haematological disorders such as Leukaemia and Haemophilia.

Special Instructions on Sample Collection and Handling

1. Follow standard precaution guidelines. Treat all samples as potentially hazardous.
2. Venous blood should be used as it has a lower margin of error.
3. Samples should be labelled with at least two separate identifying items (e.g. patient’s name and NRIC) and must be accompanied by a requisition form.
4. Sample collection time should be written on the requisition form.
5. The anticoagulant used should be as denoted by the test procedure written under ‘Specimen required’. Samples collected in anticoagulant should be well mixed by inversion at least four times. The tubes should not be shaken as mechanical trauma can induce platelet activation and/or red cell lysis. The following tubes containing certain anti-coagulants have to be noted:

   (a)	Blood for routine examinations such as Full Blood Counts and ESR	3 mL tubes containing potassium EDTA as anti-coagulant
   (b)	Blood for coagulation studies	Tubes containing 0.3 mL 3.2% sodium citrate for 2.7 mL blood, respectively
   (c)	Hb Electrophoresis	3 mL tubes containing potassium EDTA

6. Samples for haemostasis/coagulation tests must be collected in a way that preserves the integrity of easily activated or denatured proteins, enzymes and cofactors. A clean venipuncture with adequate blood flow into tubes or syringe provides the best specimen. The tubes should be filled to at least 90% full volume. In practice, ± 10% of the stated draw is acceptable. The correct order of draw should be followed to eliminate the risk of cross-contamination of additives during venipuncture and to reduce the risk of clotting in EDTA tubes. The recommended order of draw is:
   (a) blood culture tubes
   (b) sodium citrate tubes
   (c) serum and serum gel tubes
   (d) heparin and heparin gel tubes
   (e) EDTA tubes
   (f ) fluoride tubes
7. Collection of blood for coagulation testing through intravenous lines that have been previously flushed with heparin should be avoided, if possible. If the blood must be drawn through an indwelling catheter, possible heparin contamination and specimen dilution should be considered. When obtaining specimens from indwelling lines that may contain heparin, the line should be flushed with 5 mL of saline, and the first 5 mL of blood or 6-times the line volume (dead space volume of the catheter) be drawn off and discarded before the coagulation tube is filled. Prior to PT/INR testing or Factor VII assay, specimens should be maintained at room temperature to avoid cold activation of Factor VII and platelet disruption.
8. Urine Samples for Urine Sediment Microscopy, Urine Haemosiderin and Urine for fat globules should be collected as described in Bacteriology/Mycology/Parasitology Section and despatched to Haematology Lab as soon as possible as the urine sample must be examined within 1 – 2 hours of collection.

Reference Values in Haematology

There is no reliable method of defining “normal values” and the term “reference range" is used. 95% of healthy individuals have results within the reference range.

The following factors may affect the haematological values:

• The sex, age, occupation, body build, genetic and ethnic background and geographical location, especially latitude.
• The environmental and physiological conditions under which the samples are obtained, including the subject’s diet, and his posture when the sample was taken.
• The technique and timing of sample collection, transport and storage.
• Variation in the analytical method used.
• Some tests e.g. blood film and marrow morphology are observer-dependent.

Call-back Values of Analytes