How is Paget's disease diagnosed?
It has been estimated that less than 10% of patients with x-ray evidence of Paget’s disease come to medical attention. When Paget's disease is suspected, a full assessment by a hospital consultant is recommended to determine if treatment is required.
Paget's disease may be identified by an x-ray, blood test or bone scan.
In many cases, Paget’s disease is found by chance when tests are carried out for another reason.
A common blood test in general practice is to measure liver function. Included in this test is an enzyme called alkaline phosphatase (ALP). This is present in many cells within the body, but particularly in liver and bone cells (osteoblasts). If there is overactivity of the osteoblasts due to Paget’s disease, alkaline phosphatase is released into the bloodstream and can be measured.
When Paget’s disease is active, the ALP level will often, but not always, be raised. A raised ALP can stand out as being the only abnormal result. If there is co-existent liver disease, it may be necessary to perform further blood tests to identify the source of the elevated ALP.
Serum total alkaline phosphatase (ALP) is recommended as the first line blood test, in combination with liver function tests to detect Paget’s disease. If the total ALP values are normal and clinical suspicion of Paget’s disease is high, then measurement of more specialised tests such as bone alkaline phosphatase (BALP) or N-terminal propeptide of type I procollagen (P1NP) may be required.
Read Professor Fraser's article on Blood tests in Paget’s Disease of Bone, which you will find under Information in the Members' Area of this website.
When an x-ray is taken of a bone affected by Paget’s disease, characteristic features can often be seen (figure 7).
Research has shown that plain x-rays targeted to several sites, the abdomen, skull and facial bones, and both tibiae (shins), are likely to detect 93% of bones affected by Paget’s disease, compared with a single x-ray of the abdomen, which detected less (79%).
A single x-ray cannot give any information about other bones which may be affected. A radionuclide bone scan, as described below, is the best way of fully evaluating the extent of Paget’s disease.
- Bone scan
There are two types of bone scan in common use. Dual-energy x-ray absorptiometry (DEXA) scans, which are used in the diagnosis of osteoporosis, and radionuclide bone scans, used in the diagnosis of other bone conditions.
Radionuclide bone scans, also known as scintigrams, isotope bone scans or nuclear medicine bone scans, are the most helpful in Paget’s disease. A scan is recommended to determine which bones have Paget’s disease and how active the disease is. The radionuclide scan involves the use of a small amount of a radioactive tracer, which is injected into a vein in the arm. After some time, the tracer collects in the bones and pictures can be taken by a scanner (gamma camera). Information sheet (PDF): Isotope Bone Scans
A bone biopsy is a procedure in which a small sample of bone is taken and examined under a microscope. This is seldom required but can be useful if there is uncertainty about the diagnosis.
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