What is the appropriate workup for a 17-year-old with elevated alkaline phosphatase (alk phos)?

Evaluation of Elevated Alkaline Phosphatase (ALP) of 118 in a 17-Year-Old

For a 17-year-old with a mildly elevated alkaline phosphatase level of 118, the initial workup should focus on determining the tissue origin through targeted laboratory tests including isoenzyme fractionation, GGT, and liver function tests, followed by appropriate imaging based on clinical findings.

Initial Laboratory Evaluation

The first step is to determine the tissue origin of the elevated ALP:

• Liver function panel: AST, ALT, GGT, bilirubin (total and direct)

  • GGT helps differentiate between hepatobiliary vs. bone origin 1
  • If GGT is elevated, this suggests hepatobiliary origin

• Bone metabolism markers:

  • Serum calcium, phosphorus, PTH
  • 25-hydroxyvitamin D level
  • Urinary calcium/creatinine ratio 2

• ALP isoenzyme fractionation if available:

  • Helps distinguish between liver, bone, intestinal, or other origin 1, 3

• Complete blood count: To evaluate for underlying infection or malignancy

Clinical Assessment Focus Points

• Growth and development: Review growth chart and assess for growth velocity changes
• Bone pain or tenderness: Particularly in long bones
• Hepatomegaly or right upper quadrant tenderness: Suggesting liver involvement
• Recent fractures or trauma: May indicate healing bone injury
• Medication history: Some medications can cause elevated ALP
• Family history: Benign familial hyperphosphatasemia should be considered 4

Additional Considerations Based on Initial Findings

If Bone Origin Suspected:

• Plain radiographs of areas with symptoms (if present)
• Consider bone scintigraphy if there is bone pain or significantly elevated ALP 1
• Evaluate for conditions common in adolescents:
  • Growth spurt (physiologic elevation)
  • Healing fractures
  • Vitamin D deficiency

If Hepatobiliary Origin Suspected:

• Liver ultrasound: To evaluate for biliary obstruction or parenchymal disease
• Viral hepatitis serologies: Especially if transaminases are also elevated
• Autoimmune markers: ANA, anti-smooth muscle antibody if autoimmune hepatitis suspected

If Malignancy Concern:

• Targeted imaging based on symptoms
• Consider bone scan if bone pain is present 2

Interpretation of Results

• Mild elevation (as in this case) may represent:

  1. Normal physiologic variation in adolescents (growth spurt)
  2. Benign familial hyperphosphatasemia 4
  3. Early manifestation of a pathologic process

• Transient hyperphosphatasemia is a benign condition that can occur in children, characterized by marked ALP elevation without other signs of organ disease 5

Follow-up Recommendations

• Repeat ALP measurement in 4-6 weeks if mildly elevated with no other abnormalities
• Monitor growth and development at regular intervals
• Further investigation only if:
  • ALP continues to rise
  • Other laboratory abnormalities develop
  • Clinical symptoms emerge
  • ALP remains persistently elevated after 3-4 months

Common Pitfalls to Avoid

1. Overinvestigation of mildly elevated ALP in an otherwise healthy adolescent
2. Failure to consider age-appropriate reference ranges (ALP is normally higher in growing adolescents)
3. Missing family history of benign hyperphosphatasemia
4. Not considering transient hyperphosphatasemia, which can resolve spontaneously 5
5. Focusing only on serious causes when mild elevation is often benign in adolescents

Remember that while an isolated elevated ALP can indicate serious conditions like malignancy in adults 6, the context of a 17-year-old with mild elevation (118) makes benign causes much more likely, particularly growth-related bone formation.