EVALUATION OF THE AVOXIMETER - PRECISION, LONG-TERM STABILITY, LINEARITY AND USE WITHOUT HEPARIN

Objectives. Because the AVOXimeter uses disposable cuvettes and makes its measurements directly in whole blood without first hemolyzing the sample, it does not need the care and maintenance that conventional co -oximeters require, it operates faster than conventional co-oximeters, and it is less expensive. Therefore, tile objectives of this study we re (1) to evaluate the precision and linearity of the AVOXimeter's mea surements of total hemoglobin concentration and oxyhemoglobin saturati on; (2) to assess its long-term stability and thus the required interv al for recalibration; (3) to determine whether measurements can be mad e without anticoagulants; and (4) to assess the feasibility of storing blood samples in the disposable cuvettes. Methods. Measurements made by the test instrument were compared with those of conventional co-oxi meters or with standardized hemoglobin solutions. Blood samples were a lso collected with and without heparin to determine whether and-coagul ation is necessary. Results. Our tests confirmed the specified precisi on of 0.3 g/dl for total hemoglobin and 0.5% for oxyhemoglobin. The re sults also showed that these measurements were linear when compared wi th a conventional co-oximeter, and they were consistent with the speci fied accuracy of 0.45 g/dl for total hemoglobin and 1% for oxyhemoglob in. Weekly checks with control solutions showed that the instrument ho lds its calibration for a year or more. Although treating syringes wit h heparin caused dilution errors, heparin did not affect the measureme nts when dilution was avoided. When blood samples were placed in dispo sable cuvettes and read repeatedly at 1-min intervals for 20 min, the readings drifted appreciably away from the original value. This drift occurred so slowly that readings taken at the first and second minute after the cuvette was filled were within 1 or 2% of the original readi ng. Conclusions. In our experience, the test instrument was simple and easy to operate. It met the specifications for precision and accuracy , its measurements were highly linear, and it maintained a stable cali bration for one year. Ii the cuvettes are filled as soon as blood is d rawn, anticoagulation is unnecessary. However, the cuvettes should be read with 1 mill of filling the cuvette.