Specimen

Whole Blood

Collection Medium:

Minimum:

5 mL EDTA whole blood

Analytic Time:

5 days upon receipt at reference laboratory

Reference Range:

This test provides quantitative measurement of response/toxicity of 
6MP.  ProPredictRx 6MP provides red blood cell (RBC) levels of 
6-thioguanine(6TG)and 6-methyl-mercaptopurine (6-MMP).These target 
levels help monitor a patient's metabolism of azathioprine or 
6-mercaptopurine and provide information regarding the "therapeutic 
window" on an individualized basis. The 6-TG target level of >230 
pmole/8 X 10^8 RBC has been correlated with clinical remission.  
Excessive values of 6-TG have been correlated with an increased risk of 
leukopenia.  The 6-MMP level of >5,700 pmole/8 X 10^8 RBC has been 
correlated with hepatotoxicity.
Please note: 6-TG and 6-MMP assay performance validations and the 
establishment of both target therapeutic ranges and potential toxic 
thresholds were established using a gastrointestinal disease 
population. These levels should be used as a guide in monitoring 
clinical response, adjusting dosage and steroid weaning.  Levels for 
patients will vary and the therapeutic window must be established on an 
individual basis.
Routine monitoring of WBC and liver enzymes must be continued to assure 
optimized response while minimizing risk of leukopenia and drug-induced 
hepatotoxicity.   The target therapeutic range and target toxic 
thresholds were established in an IBD patient population receiving 
6-mercaptopurine or azathioprine.

Comments:

If specimen is refrigerated, specimen can be stored for five days.

Record the following items on the requisition:
Date of Birth
Gender
Ordering Doctor's Name

Test
Limitations:

Test provides quantitative measurement of response/toxicity of 6MP.
Collect specimen three weeks after beginning the therapy or after dose 
adjustment.

Methodology:

High Pressure Liquid Chromatography

CPT Code:

82491(x2)