What is the role of lab testing in the diagnosis of hypophosphatemic rickets?

Updated: May 02, 2018
  • Author: James CM Chan, MD; Chief Editor: Sasigarn A Bowden, MD  more...
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Answer

Begin clinical laboratory evaluation of rickets with assessment of serum calcium, phosphate, and alkaline phosphatase levels. In hypophosphatemic rickets, calcium levels may be within or slightly below the reference range; alkaline phosphatase levels will be significantly above the reference range.

Carefully evaluate serum phosphate levels in the first year of life, because the concentration reference range for infants (5.0-7.5 mg/dL) is high compared with that for adults (2.7-4.5 mg/dL). Hypophosphatemia can easily be missed in a baby.

Serum parathyroid hormone levels are within the reference range or slightly elevated, while calcitriol levels are low or within the lower reference range. Most importantly, urinary loss of phosphate is above the reference range.


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