Analytical validation of serum bone alkaline phosphatase (BAP OSTASE) on Liaison

The goal of this study was to validate the DiaSorin Liaison BAP OSTASE, a new method for measurement of bone alkaline phosphatase (BAP), and to compare this method with the Beckman-Coulter Access Ostase. We also wanted to establish the reference range for BAP in adults and children.

We determined the precision, functional sensitivity, recovery, linearity and measurement uncertainty, accuracy profile and beta-expectation limits. We defined an adult reference interval using individuals with 25-OH vitamin D >80 nmol/L, parathormone <58 ng/L, and normal calcium, phosphorous and estimated glomerular filtration rate. Each adult subclass (men/non-menopausal women/menopause women) contained 120 individuals. We also determined the 2.5th and 97.5th percentiles from a population of 450 children, stratified according to age and gender.

The results of the validation showed: precision <6%, functional sensitivity <0.74 microg/L, mean recovery 98.8+/-4.2% and good linearity. Relative uncertainty ranged from 9.0% to 12.9%, and the risk of one result falling out of the +/-15% acceptance limits was <5% for concentrations between 7 and 94 microg/L. The Bland-Altman plot showed no systematic bias between the two methods. In adults, we did not find any statistical difference between the different subclasses. The upper limit of normality observed in the entire population (n=360) was 21.3 microg/L (90% CI: 18.3-24.2 microg/L).

The Liaison BAP OSTASE is a robust method, and is completely validated between 7 and 93 microg/L: in this range, 95% of the values obtained will be within +/-15% of the true value.