Paediatrics: Key investigations

Key investigations

The most common reason for referral to a specialist is the identification of an abnormality on blood film.

Pancytopenia

Not all cell lines are equally affected, but the following problems occur as leukaemia or disseminated malignancy displaces normal bone marrow.

·Pallor, lethargy (low Hb).

·Bruising and/or petechiae (low platelets).

·Unexplained fever, recurrent or persistent infection (low WBC).

The following tests are used in diagnosis, staging, and assessment for prog-nosis, and as a baseline before starting treatment.

Laboratory tests

·FBC and film.

·Coagulation studies.

·Group and cross-match blood.

·Electrolytes; renal, bone, and liver profile; urate; lactate dehydrogenase (LDH).

·CRP, ESR.

·Ferritin and neuron-specific enolase (if neuroblastoma likely).

·Blood cultures.

·Thiopurine methyl transferase assay (in case of suspected acute lymphoblastic leukaemia (ALL)).

·Urine catecholamines (neuroblastoma, phaeochromocytoma).

·Lumbar puncture for cytospin, cell count, cytology.

Imaging

Sedation or general anaesthetic may be needed in young children when performing these procedures. The choice of imaging depends on the likely diagnosis, and may include:

·CXR.

·CT scan chest and/or abdomen.

·MRI scan (better than CT for soft tissue swellings and brain).

·Bone marrow aspirate and/or trephine.

·Technetium (⁹⁹Tc) bone scan.

·Meta-iodo-benzylguanidine (MIBG) scan (neuroblastoma, phaeochromocytoma).

Other investigations

These depend on the treatment being planned and may include:

·EDTA: glomerular filtration rate (nephrotoxic chemotherapy, nephrectomy).

·Audiology assessment (platinum chemotherapy, radiotherapy).

·Echocardiogram (anthracycline, pulmonary radiotherapy).

·Lung function (bleomycin, pulmonary radiotherapy).

Pituitary function (suprasellar tumours, CNS surgery or radiotherapy).