Bone Specific ALP (BALP) (BAP, BSAP, BSALP)

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). Bone marker measurements may be useful in assessment of bone turnover in metabolic bone disease, especially osteoporosis and Paget’s disease and particularly in monitoring response to therapy.

BALP 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. BALP measurement may be of use for monitoring the response to anti-resorptive therapy in metabolic bone disease, specifically with respect to CRF.

Pre-menopausal women: 5 – 16 U/L
Male: 8 – 20 U/L
The least significant change for serum BALP is ±30 %.

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. The antibody cross-reactivity with liver ALP has been reported to be approximately 7 -15%, so the assay is not suitable for patients with significant liver disease or cholestasis.

Time of collection: if monitoring response to treatment, samples should be collected at the same time of day e.g. 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 as required).

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).

Grossly haemolysed samples are unsuitable for this assay.