01Purpose and principlesWhat the assessment is for and the core concepts behind it.
Bone-marrow examination is an invasive diagnostic package rather than a single test. The decision starts with whether peripheral blood, imaging, biochemical or molecular testing can answer the question more safely. Persistent unexplained pancytopenia, blasts, a leucoerythroblastic film, suspected plasma-cell or marrow-infiltrative disease and selected staging questions commonly justify sampling. Isolated stable iron deficiency, a readily explained transient cytopenia or a clonal lymphocyte population already classifiable from blood may not. The expected effect on diagnosis or management should be recorded before consent.
Aspiration and trephine are complementary. Aspirated particles show cytological detail and permit differential counting, iron assessment, flow and many genetic techniques. A core biopsy shows overall cellularity, distribution of lineages, megakaryocytes, fibrosis, granulomas, necrosis and focal metastatic or lymphomatous infiltration. Good practice anticipates every required specimen: EDTA for morphology or molecular work, heparinised material for cytogenetics, dedicated flow medium and sterile samples for microbiology according to local laboratory instructions. Retrospective sampling is often impossible once the patient has received corticosteroids, chemotherapy or transfusion.
The posterior iliac crest procedure is usually performed under local anaesthesia with sterile technique and pressure afterwards. Pain has a sharp aspirate component and a deeper biopsy component; honest preparation, paced technique and additional analgesia or sedation in selected patients improve tolerability. Bleeding is uncommon but risk rises with severe thrombocytopenia, anticoagulation, platelet dysfunction and myeloproliferative disease. Local thresholds differ because the procedure is compressible and urgency varies; haematology and transfusion should make an individual plan rather than using an invented universal cut-off.
Key points
- Define the question before the procedure: unexplained cytopenia, suspected acute leukaemia, myelodysplasia, marrow infiltration, plasma-cell disorder, lymphoma staging, fibrosis, storage disease or fever of unknown cause each needs different samples.
- Aspiration provides individual-cell morphology, differential counts, flow cytometry, cytogenetics, molecular tests and microbiology; the trephine preserves architecture, cellularity, fibrosis, focal infiltrates and spatial relationships.
- Most adult samples come from the posterior iliac crest. Sternal aspiration is an expert-only alternative in selected circumstances and cannot provide a trephine; the sternum is not used for routine biopsy.
- Check identity, indication, consent, allergies, pregnancy status where relevant, infection, platelet and coagulation context, antithrombotic medicines, positioning and the exact laboratory containers before starting.
- A dry tap is information, not merely failure. Fibrosis, packed leukaemia, metastatic infiltration and technical factors can prevent aspiration, making trephine touch imprints and core quality especially important.
- Collect aspirate promptly because dilution increases with repeated pulls. Direct the first material to morphology and the highest-priority ancillary test agreed with the laboratory.
- A normal aspirate does not exclude patchy disease or architectural abnormality. Conversely, a hypocellular aspirate may reflect dilution and must be reconciled with trephine cellularity.
- Results require integration at a multidisciplinary level: morphology, immunophenotype, karyotype, fluorescence studies and molecular variants can conflict or describe different parts of one clonal process.
02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.
Persistent cytopenia across lineages, low reticulocytes and no reversible peripheral cause supports aspiration and trephine to assess cellularity, dysplasia, aplasia and infiltration.
Blasts, abnormal promyelocytes, rapidly worsening cytopenias, infection, bleeding or leukostasis symptoms require urgent blood and marrow classification within an emergency haematology pathway.
Dry tap, teardrops, leucoerythroblastosis, splenomegaly, bone pain or a known solid tumour raises fibrosis, myelophthisis or focal infiltration and increases trephine value.
Paraprotein, lytic bone disease, renal impairment, hypercalcaemia or unexplained anaemia may require marrow plasma-cell quantification plus flow, cytogenetics and imaging correlation.
Persistent bleeding, syncope, severe escalating buttock or back pain, neurological change, fever or wound discharge after sampling requires immediate examination and cause-directed imaging or treatment.
03Method and interpretationA systematic approach to the test and its findings.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Pre-procedure FBC, film and haemostasis reviewFirst step - Why
- Confirm the indication and plan bleeding-risk mitigation before an invasive sample.
- Interpretation and limitations
- Review platelet count, trend, clinical bleeding, anticoagulants, antiplatelets, liver or renal dysfunction and inherited bleeding history. Use local procedural policy and haematology advice rather than a single universal threshold.
- 02
Bone-marrow aspirate morphology - Why
- Assess lineage proportions, maturation, dysplasia, blasts, plasma cells, iron and infective organisms.
- Interpretation and limitations
- Quality depends on particles and limited blood dilution. The differential is interpreted with peripheral counts; morphology suggests but does not alone establish modern integrated disease classification.
- 03
Trephine histology and immunohistochemistry - Why
- Assess architecture, cellularity, fibrosis and focal or spatially distributed disease.
- Interpretation and limitations
- Core length and intact marrow spaces affect sensitivity. Histology can reveal aplasia, granulomas, lymphoma, metastatic cancer or fibrosis missed by aspirate, especially after a dry tap.
- 04
Flow cytometry - Why
- Define abnormal lineage and immunophenotype in acute leukaemia, lymphoid disease or plasma-cell disorders.
- Interpretation and limitations
- Fresh viable cells and an appropriate panel are required. Flow findings support clonality and lineage but must be reconciled with morphology and genetics, particularly after treatment.
- 05
Cytogenetic and molecular studies - Why
- Identify diagnostic, prognostic and treatment-directing chromosomal or sequence changes.
- Interpretation and limitations
- Send the correct specimen before therapy where feasible. Germline versus somatic interpretation, variant significance and measurable residual disease require disease-specific laboratory and genetics expertise.
- 06
Microbiology and special stains - Why
- Investigate selected infection, granuloma, storage or metabolic questions.
- Interpretation and limitations
- Request prospectively and use sterile material when culture is needed. A positive molecular organism signal may reflect contamination or disseminated disease and requires clinical correlation.
04Clinical next stepsHow the result changes management or prompts escalation.
01DecisionConfirm that marrow will change careFirst stepPersistent blood, clinical or imaging abnormalities raise a marrow diagnosis but immediate instability has been addressed.+
- 1Review peripheral film, reticulocytes, haematinics, haemolysis, renal, liver, infection, imaging and medicine causes first, documenting the unresolved question that marrow should answer.
- 2PreferredAlternativeThe preferred plan is combined aspirate and trephine when cellularity, architecture or infiltration matters; aspiration alone is an alternative only when the specific question is cytological and the core would not add value.
- 3EscalationEscalate urgent suspected acute leukaemia, aplasia or aggressive infiltration to the specialist team so sampling, supportive care and treatment timing are coordinated rather than scheduled routinely.
02ProcedurePrepare, sample and preserve qualityAn indicated posterior iliac crest marrow procedure has been agreed.+
- 1Complete consent and identity checks, review haemostasis and antithrombotics, position safely, mark the posterior iliac site and confirm containers, labels, transport and priority tests with the laboratory.
- 2Use sterile technique and adequate local anaesthesia; obtain the first aspirate for morphology and key ancillary work before dilution, then take an intact trephine through the trained technique.
- 3AlternativeEscalationApply firm pressure and a secure dressing, reassess pain and bleeding, document sample adequacy and complications, and escalate a dry tap by preserving trephine, touch imprints and alternative material.
03IntegrationTurn several reports into one diagnosisMorphology, flow, histology, cytogenetic or molecular results are returning at different times.+
- 1Reconcile peripheral blood, aspirate and trephine, asking whether dilution, patchy disease or treatment timing explains discordance and whether any critical preliminary result needs immediate action.
- 2PreferredUse integrated disease criteria through the preferred haematopathology multidisciplinary process; an isolated molecular variant is not automatically the disease when morphology and clinical phenotype disagree.
- 3EscalationEscalate missing, failed or inadequate studies promptly while viable material remains, communicate the working diagnosis and uncertainty, and assign ownership for final addenda and treatment review.
05Procedure and medicine safetyRelevant preparation, treatment and contraindications.
Lidocaine 1% local anaesthetic
Infiltrate skin, subcutaneous tissue and periosteum incrementally, aspirating before injection, using the smallest effective volume and staying below 3 mg/kg and 200 mg total without adrenaline.Ask about allergy, aspirate before incremental injection, include lidocaine already administered and observe for neurological or cardiovascular toxicity; use a lower limit in frailty, severe hepatic or low-output cardiac disease or when the SmPC requires it, and remember that aspiration can still cause brief deep pain.
06Risks, monitoring and follow-upComplications, safety checks and further assessment.
- Observe the puncture site, pain, pulse, blood pressure and symptoms until immediate bleeding or vasovagal effects have settled.
- Give written advice on dressing care, analgesia and urgent return for persistent bleeding, fever, discharge, severe increasing pain, weakness or numbness.
- Track aspirate, trephine, flow, cytogenetic, molecular and microbiology results through one named clinician because they mature on different timescales.
- For acute leukaemia or severe marrow failure, continue serial counts, infection, bleeding and metabolic monitoring while classification is pending.
- Review whether a non-diagnostic or discordant sample needs expert rereview, additional stains, a different site or alternative tissue rather than automatically repeating the same procedure.
07Special situationsVariants, exceptions and circumstances that change the usual approach.
The first pull is precious
Early aspirate is least diluted by peripheral blood and should be allocated deliberately to morphology and the highest-priority ancillary test.
Dry tap is a clue
Fibrosis, packed marrow and infiltration can prevent aspiration. A good trephine and touch imprints may become more diagnostically valuable than repeated suction.
Architecture changes the answer
Aspirated cells can look individually normal while the core reveals patchy lymphoma, metastatic deposits, abnormal topography or severe hypocellularity.
Variants need phenotype
Age-related clonal variants can occur without overt malignancy. Diagnosis integrates allele burden, morphology, counts, clinical context and longitudinal change.
Pain deserves preparation
Explaining the distinct pressure and brief aspirate pain, agreeing a pause signal and infiltrating periosteum properly improves trust and procedural success.
08Common pitfallsFrequent interpretation and management errors.
- 01
Requesting marrow without stating the diagnostic question or required ancillary studies.
- 02
Using aspirate alone when architecture, fibrosis or focal infiltration is central.
- 03
Drawing repeated aspirates and sending diluted material for morphology after the best sample was discarded.
- 04
Applying a universal platelet threshold without individual bleeding, urgency and local procedural guidance.
- 05
Calling a dry tap technical failure and failing to preserve the trephine and touch imprints.
- 06
Starting corticosteroids for possible lymphoma before diagnostic tissue when no emergency indication exists.
- 07
Failing to reconcile a preliminary flow result with the final integrated haematopathology report.