LABORATORY: Evaluation for Suspected Physical Injuries
In physical abuse cases the laboratory is most commonly used to help determine the presence or extent of soft tissue injuries. If there is little suspicion of significant injury after performing the history and physical, laboratory testing tends to be of limited value.
Evaluation for a Bleeding Disorder
When child abuse is suspected and bruises are present, clotting studies to evaluate for abnormal bleeding and bruising should be routine. However, if there is pattern bruising, coagulation studies may not be necessary. A detailed workup by a hematologist may be required if there is a family or patient history of a bleeding disorder or abnormal results from a screening test. However, a clotting disorder does not rule out the possibility of abuse.
Recommendations for laboratory tests related to physical injury are listed below:
A screening panel that includes CBC, platelet count, PT, PTT, and PFA-100.
CBC to determine if there is a specific hematological abnormality
Platelet count because thrombocytopenia is the most common cause of bleeding
PT (Prothrombin Time) and PTT (activated Partial Thromboplastin Time) to test for deficiencies in clotting factors
PFA-100, a platelet function assay to measure platelet activity
The most common hereditary bleeding disorder is von Willebrand disease with a prevalence of approximately 1% of the population. It may present with recurrent epistaxis, mucocutaneous hemorrhage, menorrhagia and /or excessive bruising. Normal coagulation screens do not rule out the possibility of von Willebrand's disease, although the PTT may be prolonged. With repeated bruising, appropriate testing may include blood typing, von Willebran's factor and Ristocetin Cofactor activity, Factor VIII, and a platelet count.
Bleeding times are not recommended.
The INR (International Normalized Ratio) is used for the standardization of PT across laboratories and is not a screening for coagulation factors.
Children/adolescents with intracranial bleeding should also have factor VIII and factor IX levels tested if they are male. Congenital deficiency of factor VIII has an incidence of 1 in 5000 males and factor IX deficiency has an incidence of 1 in 30,000 males. With these factors, there is also an association with prolonged bleeding of the umbilical cord and other bleeding sites.
Evaluation for Visceral Injury
Abdominal trauma is particularly ominous as the signs and symptoms of significant pathology can initially be very subtle. A complaint of abdominal pain, soft tissue evidence of abdominal trauma, or evidence of hemodynamic compromise increases the index of suspicion for intra-abdominal injury. The following injures are commonly associated with abuse: pancreatic trauma, duodenal and proximal jejunal trauma, liver trauma and pharyngeal laceration without explanation. The recommended screening tests are listed below:
Liver
Alanine aminotransferase (ALT, SGPT)
Aspartate aminotransferase (AST, SGOT)
Pancreas
Amylase
Lipase
Kidneys
Urinalysis
With physical abuse the most common use for this test is to evaluate for blood.
Bowel or rectum
Stool guaiac
A positive test could help to determine occult rectal bleeding due to abdominal or anal trauma.
Remember that the diagnosis of trauma is generally based on clinical assessments, and exhaustive evaluations for other diagnoses are usually not medically relevant.
