As noted in the previous blog, we
are developing a new test that will allow us to estimate how fast a child is
growing at the time of testing based on measuring by-products of the bone
growth process in urine and possibly blood.
The by-products, which we refer to as “biomarkers” of bone growth, are fragments
of cartilage collagen molecules (type II collagen and type X collagen) released
as bones grow in proportion to the rate or velocity of growth. Since the initial blog, we have expanded the
number of samples analyzed, especially from rapidly growing young infants and
we have improved the accuracy of the results.
The test is still under development, but our results so far are quite
encouraging.
To
date we find that both type II and type X collagen biomarker fragments
correlate well with age of normally growing children. The new results reinforce previous ones
showing that when the biomarker values are plotted against age, the graphs
mimic well established growth velocity curves for infants and children with
very high values in the youngest infants which drop during the first year and
level off after the second or third year.
The results are similar for the type II and type X collagen fragment
biomarkers, which is not surprising and actually reassuring that we are
measuring products of bone growth. We
also detect levels of the type X collagen biomarker in blood (serum) from a
limited number of normally growing infants and children and observe a strong
correlation with age as with the urine test.
As
soon as our testing procedures are optimized, we will begin to measure
biomarker levels at the same time that we measure actual growth in a small group
of children. The goal will be to
correlate biomarker levels with growth velocity determined from measuring
growth over 12 months. In other words,
biomarkers will be measured in the same infants and children we actually
measure. The results from these studies
should allow us develop an equation that will convert biomarker levels to
growth velocity rates and vice versa.
To
simulate how this might work, we turned to a study that reported how fast Dutch
children grow at different ages, which allowed us to project hypothetically how
fast our study subjects should be growing at the time the urine samples were
collected. There were a number of
differences in how the growth measurements were taken, data was handled and
ages were represented, but it is allowed us to make crude correlations between
growth velocities estimaged from the Dutch study and our biomarker
results. The results showing sizable statistical
correlations between velocity and biomarker levels exceeded our
expectations. These results strongly
support our contention that biomarkers will provide and quick and easy way to
determine growth velocity that can be used to evaluate bone growth and monitor
treatment of bone growth disorders.
