Utility of blood investigations for children and adolescents with musculoskeletal symptoms

Note: Only perform blood investigations in children or adolescents with symptoms or signs suggestive of a specific rheumatological diagnosis.

Blood investigations play a limited role in diagnosis of musculoskeletal conditions in children and adolescents. They are generally not necessary to make a diagnosis and infrequently confirm a suspected diagnosis. Always consider if the investigation result will influence your management before requesting it.

In most instances blood investigations may be corroborative; however, they can also be misleading if used out of context. Only perform blood investigations in children or adolescents with symptoms or signs suggestive of a specific rheumatological diagnosis.

If indicated by the child or adolescent’s presentation, the following blood investigations may be useful:

  • full blood count
    • raised white cell count (WCC) may indicate infection or inflammation
    • peripheral blasts or cytopenias may indicate leukaemia
  • serum electrolyte and creatinine concentrations
  • liver biochemistry
  • inflammatory markers—raised erythrocyte sedimentation rate (ESR) and serum C-reactive protein (CRP) concentration may support an inflammatory diagnosis but are nonspecific and may be normal
  • muscle enzyme concentrations—for example, raised serum creatine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) concentrations may indicate an inflammatory myopathy (eg juvenile dermatomyositis).

More specific investigations depend on the child or adolescent’s presentation and potential diagnosis; they may include: