Age-related reference intervals for creatine kinase BB in serum

Abstract

The mass concentration of creatine kinase BB (CK-BB) isoenzyme was measured in serum of 365 healthy children and adults with a CK-BB specific radioimmunoassay. Eight separate age groups (newborns, 4 days, and 1, 8, 14, 25, 40 and 65 years) were examined and the reference intervals for these groups were estimated.

The concentration of CK-BB generally decreased with increasing age, most of the changes taking place within the first year of life. Thus, the median value at age 1 year (9.2 μg/1) was 1/15th of that observed at birth, 1/2 of that observed at age 4 days, but four times higher than that observed in adults. A transient increase in CK-BB concentration was observed in boys 14 years old. At this age in contrast to at all other ages the values measured in boys were significantly (P<0.005) higher than the values measured in girls

In 27 of the sera from cord blood we also examined the relationship between estimates of CK-BB mass and activity, the latter being estimated by immuno-inhibition technique. The two estimates were highly correlated (r = 0.98), 2 μg of enzyme mass roughly equivalating 1 U of enzyme activity.

Key-words:

• activity
• gaussian distributed
• mass
• radioimmunoassay
• specific