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Step 3: Assay Limitation Sheet

• Definition. An Assay Limitation Sheet is a table that summarizes the effects of interference of HBOC on listed assays and is limited to the specific instrument under the conditions of the testing environment (e.g., reagents). For example, the below table is an Assay Limitation Sheet for the i-STAT analytical system from testing performed by the IVD Manufacturer.
  
  Assay Limitation Sheet of acceptable concentrations of OPK Biotech products used with the i-STAT analysis system:
  
  
  
• How to Use an Assay Limitation Sheet.
• Once the plasma hemoglobin (assumed to be Hemopure or Oxyglobin) in the patient's specimen is measured, the expected amount of interference is determined using an Assay Limitation Sheet as follows:
• Compare the measured plasma hemoglobin (STEP 2) of the specimen with the hemoglobin concentration limits for the desired assay.
• If the measured plasma hemoglobin (HBOC) is equal to or higher than the hemoglobin concentration limit on the Assay Limitation Sheet, then that assay is not accurate in the presence of Hemopure or Oxyglobin and the assay should not be performed and/or results should not be reported.
• If the measured plasma hemoglobin (HBOC) is lower than the concentration on the Assay Limitation Sheet, then the specimen can be assayed accurately for that analyte and results reported (Step 4).
• Example (using Assay Limitation Sheet for i-STAT instrument, above).
• A patient specimen arrives containing Hemopure and both creatinine and glucose tests have been requested.
• You measure the specimen's plasma hemoglobin and it is 5 g/dL.
• You review the Assay Limitation Sheet, specific for the instrument you will be using. The plasma hemoglobin value is higher than the plasma hemoglobin creatinine limit (3.9 g/dL) and thus creatinine will not be accurate. However, this plasma hemoglobin value is lower than the glucose limit (6.5 g/dL) and thus glucose will be accurate.
• Creatinine is not analyzed and the laboratory data sheet indicates that creatinine is not available due to the presence of the HBOC. A notation is made to request test when HBOC is less than 3.9 g/dL.
• Glucose is analyzed and results reported to the physician.
• Sources of Assay Limitation Sheets
• Individual Laboratory Data. Your laboratory may have directly tested its instruments for interferences from Hemopure or Oxyglobin and have an Assay Limitation Sheet available for those specific instruments, using the laboratorys choice of reagents and operated under the standard operating procedures of the hospital. Check with appropriate hospital personnel.
• IVD Instrument Manufacturing Data. The most knowledgeable source of information on instrument performance and likely effects of possible interferences with HBOC is the IVD manufacturer of your laboratory instrument. The manufacturer should be contacted via its Technical Service department to see if such information is available. Some IVD manufacturers have presented or published results from investigations of possible interferences with HBOC (EXISTING DATA: IVD data).
• Clinical Trial Interference Data for HBOC.
• Hemopure: Data were compiled from direct interference testing of varying concentrations of Hemopure against known analyte concentrations on laboratory instruments used at OPK Biotech's human clinical trial laboratories from 1994 to 2006. Summary Assay Limitation Tables (Existing Data: Trial Data) are available; however, no control was exerted to standardize the method in which these instruments were used; instrument Standard Operating Procedures as well as the type of reagent may have differed among testing sites.
• Go to Step 4.