What labs should be ordered for a 7-year-old female with bruising on several areas of the body?

Laboratory Workup for a 7-Year-Old with Widespread Bruising

Order a complete blood count with platelet count and peripheral smear, PT, aPTT, and fibrinogen level as your initial screening panel. 1

Essential First-Line Laboratory Tests

The initial screening must include these four core tests:

• Complete blood count (CBC) with platelet count and peripheral blood smear to identify thrombocytopenia, abnormal platelet morphology, or hematologic malignancies 1
• Prothrombin Time (PT/INR) to evaluate the extrinsic coagulation pathway and detect vitamin K deficiency, liver disease, or factor VII deficiency 1
• Activated Partial Thromboplastin Time (aPTT) to assess the intrinsic coagulation pathway and screen for hemophilia and other factor deficiencies 1
• Fibrinogen level to detect fibrinogen disorders that routine PT/aPTT testing will miss 1

Critical Pitfall: Normal Screening Does NOT Rule Out All Bleeding Disorders

Normal PT and aPTT results do not exclude von Willebrand disease, Factor XIII deficiency, or platelet function disorders. 1 This is the most important pitfall to recognize, as von Willebrand disease is the most common inherited bleeding disorder (prevalence 1 in 1000) yet standard coagulation tests fail to detect it. 2

Additional Testing Based on Clinical Context

If Initial Screening is Normal but Clinical Suspicion Remains High:

• Von Willebrand factor testing panel including VWF antigen, VWF ristocetin cofactor activity, and Factor VIII coagulant activity should be performed 1
• Platelet function testing (such as platelet aggregation studies) when platelet count is normal but clinical suspicion for platelet dysfunction exists 1
• Factor XIII assay if other tests are normal but severe bruising persists, as this deficiency is not detected by standard coagulation tests 1

Pediatric-Specific Additional Tests:

• Serum calcium, phosphorus, alkaline phosphatase, parathyroid hormone, and 25-hydroxy-vitamin D to evaluate bone metabolism disorders 1
• Serum copper and ceruloplasmin to screen for metabolic disorders 1

Key Clinical Assessment Points Before Ordering Labs

Before ordering any laboratory tests, assess whether testing is even warranted:

• Pattern and location of bruising: Bruising on buttocks, ears, genitals, or patterned bruising has higher specificity for abuse and may not require bleeding disorder workup 3, 4
• Bleeding history: Significant bleeding after circumcision, surgery, dental procedures, epistaxis, or umbilical stump bleeding increases likelihood of a bleeding disorder 3, 4
• Family history: Specific bleeding disorders or ethnicity associated with higher rates of certain bleeding disorders (e.g., Amish populations) 3, 4
• Medication review: Document all medications and alternative therapies that may increase bleeding/bruising 3, 4

In some cases, the constellation of findings can be so strongly consistent with abusive injury that laboratory investigation for bleeding disorders is not warranted. For instance, a child with a patterned slap mark who describes being hit does not require bleeding disorder evaluation. 3

Important Timing Consideration

If blood product transfusions have been given, delay screening for bleeding disorders until elimination of transfused clotting elements. 2

When to Refer to Hematology

Referral to hematology is indicated when:

• Initial laboratory evaluation indicates a bleeding disorder 4
• High clinical suspicion remains despite normal laboratory workup 4
• Specialized testing is needed (platelet function studies, VWD multimer analysis, Factor XIII assay) 4

Special Consideration for Non-Accidental Trauma

Non-accidental trauma must be considered in the differential diagnosis, particularly in children under 24 months. 1 The age and developmental capabilities of the child should be assessed to determine if bruising location is consistent with normal activity. 4 Children who are verbal should be interviewed away from potential offending caregivers if possible. 3

Laboratory testing suggestive of a bleeding disorder does not eliminate abuse from consideration in children with intracranial hemorrhage. 2

Laboratory Quality Considerations

Coagulation tests are very sensitive to specimen handling and should be performed in experienced laboratories, as inappropriate handling commonly leads to false-positive results. 2 Be aware that aPTT can be falsely prolonged with lupus anticoagulant or Factor XII deficiency (which does not indicate a true bleeding disorder). 2