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Diagnosis and tests

How ALL is diagnosed

The related article (“ALL: symptoms and diagnosis”) explains the blood smear. This topic shows the path to an ALL diagnosis: how the B or T type, the genetic subtype and the CNS status are determined.

Last updated: ~1 min read
A path with two signposts.
Figure 1.A fork between B and T.

01Short answer

ALL is usually suspected from a blood count showing anaemia, low platelets and blasts. The diagnosis is confirmed with a bone marrow aspiration: lymphoblasts are usually more than 20%. Flow cytometry plays the key role: it shows whether it is B-ALL (CD19, CD22, CD79a) or T-ALL (cytoplasmic CD3), and it creates a “marker map” for later MRD testing. Cytogenetics, FISH and molecular tests define the genetic subtype: the Philadelphia chromosome (BCR::ABL1), KMT2A rearrangements, ETV6::RUNX1, hyperdiploidy, Ph-like ALL and others. This determines the risk group and whether targeted drugs are used. A lumbar puncture checks whether leukaemia has reached the CNS. In T-ALL, a chest X-ray or CT looks for a mediastinal mass.

02Simple explanation

B or T: flow cytometry.

Genetic subtype: risk and treatment.

CNS: lumbar puncture.

03Scientific explanation

Ph-like ALL: a subtype without the Philadelphia chromosome but with similar gene activity; sometimes changes suitable for targeted treatment are found.

Children and adults: favourable subtypes (hyperdiploidy, ETV6::RUNX1) are more common in children, and Ph+ ALL is more common in adults.

04What happens in the body?

B or T

Flow cytometry shows which path the ALL has taken.

Spinal fluid and marrow

Both the bone marrow and the spinal fluid are checked.

Two tubes side by side.
Figure 2.Spinal fluid and marrow samples.

A genetic mosaic

Each genetic subtype is like a separate tile.

A mosaic of coloured tiles.
Figure 3.A mosaic of genetic subtypes.

05Diagnosing ALL

Four steps.

Blood — Blasts.1BloodBlasts.
Marrow — Flow cytometry.2MarrowFlow cytometry.
Spinal fluid — CNS status.3Spinal fluidCNS status.
Genes — Subtype.4GenesSubtype.

06Tests in diagnosing ALL

TestPurpose
Blood countSuspicion
Marrow aspirationLymphoblast percentage
Flow cytometryB or T, baseline for MRD
Cytogenetics, FISH, PCRPh, KMT2A, ETV6::RUNX1
Lumbar punctureCNS status
Chest imagingMediastinal mass (T-ALL)

07Key terms

ALL
Acute lymphoblastic leukaemia.
B-ALL / T-ALL
ALL arising from B or T cells.
Hyperdiploidy
Extra chromosomes.
Ph-like ALL
A gene profile resembling Ph+.
CNS status
Whether leukaemia has reached the spinal fluid.

08Key points

  • ALL is confirmed by a marrow test.
  • Flow cytometry shows B or T.
  • Genetics gives the subtype.
  • Ph+ ALL affects targeted treatment.
  • A lumbar puncture checks the CNS.
  • Results are read together.

09Frequently asked questions

Why is a lumbar puncture done?

To see whether leukaemia has reached the spinal fluid (“Lumbar puncture and cerebrospinal fluid”).

What does Ph+ mean?

BCR::ABL1 is present; targeted drugs may be added to treatment (“BCR::ABL1 and the Philadelphia chromosome”).

Is diagnosis different in children?

The steps are the same; procedures are often done under anaesthesia.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. Why is a lumbar puncture done?

  2. What does Ph+ mean?

  3. Is diagnosis different in children?

My questions

12Sources

  1. National Cancer Institute (NCI). Adult ALL treatment (PDQ), patient version
  2. MedlinePlus. Cerebrospinal fluid (CSF) analysis
  3. MedlinePlus. Bone marrow tests
  4. MedlinePlus (U.S. National Library of Medicine). Ultrasound
  5. MedlinePlus (U.S. National Library of Medicine). Nuclear Scans
  6. NHS. CT scan
  7. NHS. MRI scan
  8. NHS. Ultrasound scan
  9. NHS. PET scan
  10. MedlinePlus. Cerebrospinal fluid (CSF) collection
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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