Imperial Collage Healthcare

Bone Specific ALP (BALP)


Test Background
This assay quantitatively measures the bone-specific isoenzyme of alkaline phosphatase (BALP) in serum, a product of the osteoblast during bone formation, and is therefore an assessment of bone turnover (specifically formation). The antibody cross-reactivity with liver ALP has been reported to be approximately 7 %, so the assay is not suitable for patients with significant liver disease or cholestasis.”


Clinical Indications
The most useful application of BALP measurement is to monitor the response to anti-resorptive therapy in metabolic bone disease, eg. treatment of osteoporosis with oral alendronate therapy, or treatment of Paget’s disease with intravenous pamidronate. It is the marker of choice for the diagnosis and monitoring of Paget’s disease. A baseline pre-treatment sample is taken, followed by serial samples post-treatment, eg. after 3 and 6 months.


Reference Range

Pre-menopausal women 6.5 – 14.9 IU/L
Males 8.0 – 19.5 IU/L
The least significant change for serum BALP is ±30 %.


Please note that from March 2014, due to the reformulation of Bone Specific ALP activity kits, results are now approximately 50% lower than those seen previously. New reference ranges are provided above. The least significant change for serum BALP is still +/-30% If you would like to discuss this particular issue please contact Dr. Alan Courtney directly (alan.courtney@imperial.nhs.uk, Tel 0203 311 5187/5185, Fax 0203 311 5184).


Note that post-menopausal reference ranges are poorly defined, and patients who are being treated for osteoporosis should be targeted to reduce their bone turnover into the bottom half of the pre-menopausal range. A post-menopausal reference range is available on request and is suitable for research studies only. BALP levels are higher in children than in adults, by as much as 5-10 fold.


Sample Required
Serum (red top) or heparin (green top). EDTA (lavender top) samples are unsuitable.Store frozen at -20 ºC if not sent same day as collected.


Sample Volume
0.5 mL


Turnaround Time
3 weeks


Notes
If monitoring response to treatment, samples should be collected at the same time of day, eg. always a morning clinic, or always an afternoon clinic. Ideally a morning fasting sample should be collected. Serial measurements on the same patient are recommended before therapy and at 3 and 6 months after therapy (and at subsequent 3, 6 or 12 monthly intervals).

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