Evaluation of the macro- vue latex agglutination test for quantitation of gentamicin in human serum

The Macro-Vue Card Test (Hynson, Wescott, and Dunning, Baltimore, MD.) for rapid quantitation of gentamicin in serum was compared with bioassay and radioimmunoassay procedures on sera from 100 patients. Regression analysis of paired results from the bioassay (using Klebsiella pneumoniae ATCC 27799) and the Macro-Vue Card Test indicated a correlation coefficient of 0.89, whereas comparing radioimmunoassay and Card Test results yielded a correlation coefficient of 0.83. The bioassay-radioimmunoassay correlation coefficient was 0.88. The data were further examined by grouping the sera of the patients into three categories based on therapeutic concentration ranges as follows: <2 μg/ml, subtherapeutic range; 2 to 8 μg/ml, therapeutic range; >8 μg/ml, potentially toxic range. Of 100 specimen values, 81 fell into the same concentration range when bioassay and Card Test values were compared. Of the 19 disagreements, 12 were considered minor. Of 100 specimen values compared by radioimmunoassay and the Card Test, 88 fell into the same concentration range. Of the 12 disagreements, 6 were considered minor. Therefore, the Macro-Vue Card Test for gentamicin compared favorably with both the bioassay and radioimmunoasay procedures. The minimal time required to perform the Card Test (12 to 15 min) makes it attractive for situations in which immediate results are needed.