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A Program for Identifying Laboratory Assay Interferences by Hemoglobin Based Oxygen Carriers (HBOC)

P.F. Moon-Massat, L.A. Watrous, and M.S. Gawryl
Biopure Corp., Cambridge, MA

Hemopure (HBOC-201, Biopure Corp. Cambridge, MA), an oxygen therapeutic (red blood cell substitute) that circulates in the serum, interferes with many routine chemistry assays in an unpredictable fashion. Hence, patient safety requires that the blood samples from HBOC-treated patients be analyzed only on previously evaluated laboratory equipment and the interpretation of results be performed exclusively by trained laboratory personnel.

Biopure Corp. has addressed this problem by developing a two-pronged program aimed at collaborating with in vitro diagnostic (IVD) equipment manufacturers and hospital laboratory personnel. First, IVD manufacturers are characterizing HBOC-201 interference on their own equipment and many will be able to provide literature on degree of HBOC interference soon. Until then, individual hospital laboratories involved in HBOC clinical trials must undertake a similar HBOC interference challenge to determine laboratory-specific interferences. For the hospital challenges, samples with varying concentrations of HBOC-201 (0 to 6.5 g/dL) are provided in triplicate for each machine. A summary Assay Limitations Guideline (AGL) is produced and used to indicate the specific plasma hemoglobin concentration at which results for that analyte are no longer accurate. In general, data are considered accurate if the change in assay results due to the presence of HBOC-201 deviate from the baseline results by not more than 5% for electrolytes, 20% for enzymes, and 10% for other analytes. Trained laboratory personnel determine the patients serum hemoglobin and, using the AGL, determine which tests will be accurate. These results are reported and all others are designated as unable to quantitate. Critical to this process is for laboratory personnel to become accustomed to the hemolyzed appearance of a specimen from an HBOC-treated patient.