Sequential Testing

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 Below are listed sequential tests that may be required for appropriate results to be given, which may delay the release of the result of the initial test while they are being performed. These will be performed as and when required by the laboratory staff, and are listed here for reference only.

 Unauthorised tests that are part of a set of requests made on a single form may also hold up the hard copy report of the results, but should not hold up electronic reporting.

 Some tests may require sending to external laboratories due to issues with specific samples, or analyser downtime. For more information on any specific sendaway test, see the Haematology Test Information section.







Full Blood Count (FBC)

Repeat run

To obtain correct results if the analyser incorrectly aspirates a sample, or requires further red cell indices such as a reticulocyte count or nucleated red cell count.

Dilution run

To correct white blood cell counts (WBCs) that are higher than the analytical range of the analyser.

Lipaemia check and correction

To correct the erroneously high haemoglobin concentration caused by interference from highly lipaemic plasma.

Cold haemagglutinin adjustment

To prevent red blood cells from clumping together by warming the sample long enough for cold-reacting antibodies to lose adhesion.

Pseudothrombocytopaenia correction

To obtain a correct platelet count for those patients whose platelets aggregate in standard ETDA-anticoagulated sample tubes. The Haematology laboratory has a supply of Sarstedt Thromboexact sample tubes for this purpose; if it is deemed necessary for them to be used, then the laboratory should be contacted to arrange delivery.

Reticulocyte count

To determine red cell turnover and investigation of anaemia & haemolysis

Film examination

To identify morphological features of blood cells when the FBC does not give sufficient information to be of clinical use. This may lead to further testing if the blood film is not conclusive by itself.

Paul Bunnell Screen

To test for the presence of heterophile antibodies that might indicate Infectious Mononucleosis, where blood film morphology and red cell indices are suggestive of the possibility.

Haemoglobinopathy Screen

To test for haemoglobinopathies where blood film morphology and red cell indices are suggestive of the possibility.


Haemoglobinopathy Screen

Sickle Solubility

To determine if there is any haemoglobin S (HbS) present.

Hb Electrophoresis

Confirmation method to determine which haemoglobin variants are present. (More information about what is detected at PCH can be found under haematology test information)

Malaria investigations


G6PD screen

To determine if the patient is glucose-6-phosphate dehydrogenase deficient, which may necessitate a change in the antimalarial therapy given.

Reticulocyte Count

To determine red cell turnover and possible parasite haemolysis. Also, to determine if a mild G6PD deficiency is being masked by reticulocytosis.







APTT, PT Fibrinogen and Thrombin Time

Manual assay

To mechanically detect clot formation, for when a sample's plasma interferes with the analyser's optical clot detection method.

D Dimer assay

To determine the presence of D Dimer fibrin degradation products. This test will automatically be added on if the laboratory staff suspect the presence of Disseminated Intravascular Coagulation (DIC).



APTT assay using phospholipid insensitive reagent

To identify if an extended APTT is potentially due to antiphospholipid antibodies.

Dilution assay

To determine if an extended APTT is due to a deficiency in one of the intrinsic clotting factors, or a clotting inhibitor.


Dilution assay

To determine if an extended PT is due to a deficiency in one of the extrinsic clotting factors.

Thrombotic screen

Thrombotic markers

To determine whether any abnormal thrombotic screen results are due to either the Factor V Leiden G1691A or Prothrombin G20210A mutations.


Thrombotic screen requests made where historic results exist on a patient are intervened.