From the Guidelines
An alkaline phosphatase (ALP) level of 133 in a 64-year-old woman is mildly elevated and warrants further evaluation to determine the underlying cause, with a focus on differentiating between hepatic and non-hepatic origins, as suggested by the American College of Radiology in their 2023 guidelines 1. The first step should be to repeat the test to confirm the elevation and check other liver function tests including AST, ALT, GGT, bilirubin, and albumin.
- Additional testing should include a hepatitis panel, abdominal ultrasound, and bone-specific ALP to determine the source of elevation.
- Common causes in this age group include medication effects, biliary obstruction, bone disorders like Paget's disease, or liver conditions, as outlined in the study published in the Journal of the American College of Radiology 1. If the patient is asymptomatic and other liver tests are normal, watchful waiting with repeat testing in 3-6 months may be appropriate.
- However, if she has symptoms like right upper quadrant pain, jaundice, pruritus, or bone pain, more urgent evaluation is needed, considering the potential for cholestatic liver disease or other serious conditions 1. ALP is produced primarily in the liver and bones, and elevations can indicate cholestasis (bile flow obstruction) or increased bone turnover, as noted in the study 1.
- Age-related changes can cause mild ALP elevations, but levels above the reference range should not be dismissed as normal aging, and further investigation is necessary to rule out underlying pathology, in line with the recommendations from the American College of Radiology 1.
From the Research
Alkaline Phosphatase Levels in Paget's Disease
- An alkaline phosphatase (ALP) level of 133 in a 64-year-old woman may be indicative of Paget's disease of bone, a common bone disorder characterized by disorganized bone remodeling 2, 3.
- Elevated serum ALP levels correlate with disease activity in Paget's disease, and an ALP level of 133 may suggest active bone remodeling 2, 4.
- However, it is essential to note that ALP levels can be influenced by other factors, such as liver disease, and therefore, should be interpreted in conjunction with other diagnostic tests, including radiographs and nuclear scintigraphy of the bone 2, 5.
Diagnosis and Management of Paget's Disease
- The diagnosis of Paget's disease is typically made based on characteristic radiographic findings and elevated ALP levels 2, 3.
- Bisphosphonates, such as zoledronic acid, are the mainstay of treatment for Paget's disease, and are recommended for patients with symptomatic disease 2, 3, 4.
- Treatment aimed at improving symptoms is recommended over a treat-to-target strategy aimed at normalizing total ALP in Paget's disease 4.
Interpretation of Alkaline Phosphatase Levels
- The measurement of bone-specific alkaline phosphatase (BAP) may provide a more accurate assessment of bone cell function than total ALP levels 5.
- BAP levels have been shown to correlate better with total ALP levels than with bone Gla protein (BGP) levels in patients with Paget's disease 5.
- The interpretation of ALP levels should take into account the percentage of bone tissue affected by the disease, as localized forms of Paget's disease may have high alkaline phosphatase activity despite relatively low ALP levels in the blood 6.