A patient with acute lymphoblastic leukemia (ALL) may be treated with L-asparaginase in order to cause depletion of L-asparagine.


L-asparagine is measured using HPLC and reported in µmol/L.


L-asparaginase is measured as enzyme activity with units of IU/L.


Measurement of L-asparagine in plasma can be difficult in a patient receiving L-asparaginase since the enzyme may continue to function in vitro (after specimen collection) unless the specimen is immediately frozen or the enzyme is otherwise inactivated.


Goal of therapy:

(1) depletion of L-asparagine (to unmeasurable levels)

(2) trough L-asparaginase activity above the target cutoff (usually the recommended level is > 100 IU/L. but L-asparagine depletion may occur at trough levels < 50 IU/L)


Measurement of L-asparagine or L-asparaginase may be helpful:

(1) to confirm adequate dosing

(2) after long-term use to confirm efficacy

(3) if antibodies to the enzyme are suspected

(4) disease progression despite adequate therapy


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