What is the most appropriate initial investigation for a child presenting with bruising and petechiae of unknown cause?

Full Blood Examination is the Most Appropriate Initial Investigation for a Child with Bruising and Petechiae

A full blood examination (FBE) is the most appropriate initial investigation for a 6-year-old boy presenting with a one-week history of bruises and generalized scattered petechiae. 1

Rationale for Full Blood Examination

• FBE provides critical baseline information about potential bleeding disorders that can cause bruising and petechiae, including assessment of platelet count, red blood cell parameters, and white blood cell counts 1
• The American Academy of Pediatrics recommends that initial testing for children with bruising/bleeding should focus on the prevalence of potential conditions and their likelihood to cause the specific findings 1
• FBE is less invasive and more readily available than other investigations, making it an ideal first-line test 2

Clinical Approach to Bruising in Children

When to Consider Bleeding Disorders vs. Child Abuse

• Both bleeding disorders and child abuse must be considered in a child presenting with unexplained bruising 1
• Key factors that increase suspicion for bleeding disorders include:
  • Pattern of bruising (spontaneous bruising in multiple locations)
  • Presence of petechiae (small pinpoint hemorrhages)
  • Otherwise well appearance of the child 1

Investigation Algorithm

1. Start with Full Blood Examination 1

   • Assesses platelet count and morphology
   • Evaluates for anemia or other cell line abnormalities
   • Can identify leukemia or other hematologic malignancies that may present with bruising

2. If FBE abnormal, proceed with:

   • Coagulation profile (PT, aPTT) 3
   • Further specialized testing based on initial results 4

3. If FBE normal but clinical suspicion remains high:

   • Consider coagulation profile and specialized testing for von Willebrand disease or other rare bleeding disorders 4
   • Consider skeletal survey if child abuse is suspected (particularly in children <24 months) 1

Important Considerations

• Sample handling is critical for accurate FBE results - improper collection or transport can lead to false platelet clumping or other artifacts 5
• The presence of a bleeding disorder does not rule out the possibility of child abuse - both conditions can coexist 1
• For children with bruising suspicious for abuse, complete medical, trauma, and family histories along with thorough physical examination are essential alongside laboratory testing 1

Pitfalls to Avoid

• Jumping directly to coagulation studies without first obtaining a baseline FBE can lead to unnecessary testing and blood draws 3
• Skeletal surveys are not indicated as first-line investigations in children >24 months without specific signs of trauma or abuse 1
• Relying solely on laboratory findings without considering the clinical context can lead to missed diagnoses 2

Follow-up Testing

• If the FBE is abnormal, consultation with a pediatric hematologist is recommended for further specialized testing 1
• If child abuse is suspected based on clinical findings and normal FBE, appropriate child protection measures should be initiated alongside any additional investigations 1