Laboratory Testing to Confirm Paget Disease of Bone
Serum total alkaline phosphatase (ALP) measured in combination with liver function tests is the primary biochemical screening test to confirm Paget disease of bone. 1, 2
Primary Diagnostic Laboratory Test
- Serum total alkaline phosphatase (ALP) is the first-line biochemical test and should always be measured alongside liver function tests to exclude hepatic causes of elevated ALP 1, 3, 2
- Elevated ALP correlates directly with disease activity and the extent of skeletal involvement 3, 2
- The combination with liver function tests is essential because ALP elevation alone is non-specific and can be elevated in liver disease 1, 2
Additional Confirmatory Laboratory Tests
When Paget disease is suspected, the following metabolic panel should be obtained to exclude other metabolic bone diseases:
- Serum calcium levels to rule out hyperparathyroidism and other calcium disorders 4, 1
- 25-hydroxy-vitamin D levels to exclude osteomalacia 4, 1
- Phosphate levels to assess for hypophosphatasia and other phosphate disorders 4, 1
- Parathyroid hormone (PTH) levels to differentiate from primary hyperparathyroidism 4, 1
Specialized Bone Turnover Markers
- Procollagen type I N-terminal propeptide (PINP) or C-terminal telopeptide (CTX) can be used when additional confirmation is needed beyond total ALP 4, 1
- These markers should be measured in fasting blood samples for optimal accuracy 4
- They provide more specific assessment of bone formation (PINP) and bone resorption (CTX) activity 4, 1
Important Clinical Caveats
Laboratory tests alone do not confirm the diagnosis—they must be interpreted in conjunction with characteristic radiographic findings on plain X-rays or positive radionuclide bone scintigraphy 3, 5, 2. The diagnosis is ultimately confirmed by the combination of elevated ALP with characteristic imaging findings showing mixed osteolytic and osteosclerotic lesions 1, 3.
A common pitfall is misdiagnosing hyperparathyroidism based on elevated ALP and calcium levels, when the actual diagnosis is Paget disease 6. Always correlate biochemical findings with imaging studies before finalizing the diagnosis 3, 2.