Age
The effect of age ❚Table 1❚ on laboratory results has
been well recognized to the point that separate reference
intervals have been used to distinguish pediatric, adolescent,
adult, and geriatric populations. Bone growth and development
in a healthy growing child is characterized by increased
activity of bone-forming cells, the osteoblasts, that secrete
the enzyme, alkaline phosphatase. Hence, the activity of this
enzyme is approximately 3 times higher in a growing child
compared with the activity in a healthy adult.3,4
A substantial increase in the RBC count in the neonates
compared with that in adults is the reason glucose is metabolized
very rapidly in neonates.2 Increased arterial oxygen
content within a few days of birth leads to an increase in
hemoglobin levels owing to the destruction of the RBCs.
Serum bilirubin levels then increase, because the immature
liver lacks enzymes to convert bilirubin to the water-soluble
bilirubin diglucuronide.2 The total number of neutrophils are
at a maximum for 1 to 2 days after birth. In the neonate, the
monocyte count is increased for up to 2 weeks after birth,
while the eosinophil count stays elevated for up to 1 week
after birth.5,6 The lymphocyte count is increased markedly at
birth and remains elevated in children up to 4 years of age.6
In contrast, the basophil count is elevated only transiently for
up to 1 day after birth. A substantial decrease in serum uric
acid levels is noted between days 1 and 6 after birth.2
AgeThe effect of age ❚Table 1❚ on laboratory results hasbeen well recognized to the point that separate referenceintervals have been used to distinguish pediatric, adolescent,adult, and geriatric populations. Bone growth and developmentin a healthy growing child is characterized by increasedactivity of bone-forming cells, the osteoblasts, that secretethe enzyme, alkaline phosphatase. Hence, the activity of thisenzyme is approximately 3 times higher in a growing childcompared with the activity in a healthy adult.3,4A substantial increase in the RBC count in the neonatescompared with that in adults is the reason glucose is metabolizedvery rapidly in neonates.2 Increased arterial oxygencontent within a few days of birth leads to an increase inhemoglobin levels owing to the destruction of the RBCs.Serum bilirubin levels then increase, because the immatureliver lacks enzymes to convert bilirubin to the water-solublebilirubin diglucuronide.2 The total number of neutrophils areat a maximum for 1 to 2 days after birth. In the neonate, themonocyte count is increased for up to 2 weeks after birth,while the eosinophil count stays elevated for up to 1 weekafter birth.5,6 The lymphocyte count is increased markedly atbirth and remains elevated in children up to 4 years of age.6In contrast, the basophil count is elevated only transiently forup to 1 day after birth. A substantial decrease in serum uricacid levels is noted between days 1 and 6 after birth.2
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