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A 5-year-old child with a previous fracture right foot had a serum Alkaline Phosphatase (ALP) of 840 U/L (High),  a serum phosphate of 3.5 mg/dL (Normal),and a serum γ-glutamyl transferase(GGT) of 30 U/L (Normal). There was no history of fever or any other medical illness.
After the clotted blood was spun down in the test tube, the serum was visibly hemolyzed owing to difficulty in obtaining the specimen. The physical examination of the child was unremarkable.
Why is the normal range of ALP higher in children than in adults?
What is the significance of a hemolyzed serum sample and the elevated serum ALP?
What is the most likely cause of the elevated ALP?

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One Response to Case study- Elevated Serum Alkaline phosphatase Level

  • 1. For bone mineralisation to take place, the availability of phosphate ions is crucial. Alkaline phosphatase (ALP) is abundantly found in osteoblast cells whereby they make phosphate ions available from organic phosphates for bone mineralisation. Children are in a period of active growth which is characterised by rapid bone growth. This implies a high osteoblastic activity in children and hence a physiologically higher level of ALP in them.

    2. UNCERTAIN OF ANSWER (but I will try)…

    EITHER: ALP works at an optimum pH of 9-10. A change in blood pH can cause lysis of the RBC plasma membrane, leading to haemolysis.

    OR: ALP levels are so high that they have started removing phosphates from phospholipids, leading to disruption of the RBC plasma membrane and hence haemolysis.

    3. Since the child presented with a previous fracture, it can be inferred that the fracture is now healing. This implies a higher osteoblastic activity and hence an elevated serum ALP.