A K Gong1, B Backenstose. 1. Department of Pediatrics, University of Texas Health Science Center, San Antonio, TX 78284-7812, USA. gong@uthscsa.edu
Abstract
OBJECTIVE: The Hb-Quick is a new portable hemoglobinometer that uses disposable cuvettes to measure the total hemoglobin concentration of capillary, venous, or arterial blood. Therefore, the objectives of this study were 1) to evaluate the performance of this compact, battery-powered hemoglobinometer by assessing its precision, accuracy, and linearity, 2) to determine whether its measurements suffer from interference by hemolysis, bilirubin, fetal hemoglobin, or hemodilution, and 3) to establish whether it can easily be used by clinical personnel with little or no laboratory training. METHODS: The precision of the test instrument was assessed by making repeated measurements on blood samples. Its accuracy and linearity were evaluated by comparing its measurements with the internationally accepted cyanmethemoglobin method. Samples of whole blood with and without bilirubin, fetal hemoglobin, hemolysis, and hemodilution were also analyzed to determine if any interference occurred when these disturbances were present, and it was placed in physicians' offices to evaluate its use by non-laboratory personnel. RESULTS: Repeated measurements on blood samples with a wide range of hemoglobin concentrations were consistent with the precision specification (0.25 g/dl). The bias of the new hemoglobinometer was calculated as the mean difference between its readings and measurements with the cyanmethemoglobin method, and its accuracy as the standard deviation of the differences between the two methods. As assessed in this manner, the new hemoglobinometer had a bias of -0.04 g/dl and an accuracy of 0.40 g/dl. The linearity was checked over a hemoglobin concentration range from 0 to nearly 30 g/dl. There was a highly significant linear relationship between its readings and measurements with the cyanmethemoglobin method (slope = 0.997, y-intercept = 0.005, r = 0.999). Complete hemolysis of the sample increased the readings on average by only 0.22 g/dl. Bilirubin (17.5 mg/dl) increased the reading by an average of 0.29 g/dl, and fetal hemoglobin (76.5% HbF) reduced the readings by an average of only 0.035 g/dl. Diluting blood samples with saline also did not appreciably affect its accuracy. CONCLUSIONS: The new hemoglobinometer is fast and easy to operate. No sample preparation or pipetting is required. To operate the instrument, the user simply allows a drop of blood to fill the disposable cuvette by capillary action and inserts the cuvette into the instrument. The instrument analyzes the 10 microl sample and displays the results in less than 10 seconds. The interference caused by hemolysis, hemodilution with saline, fetal hemoglobin, and bilirubin were too small to be of any dinical importance. Tests in physician's offices indicated that clinical personnel with little or no formal laboratory training could successfully use this device. The observed precision, accuracy, linearity, and freedom from interference indicate that this hemoglobinometer is suitable for near-patient testing in a wide range of clinical settings including physicians' offices.
OBJECTIVE: The Hb-Quick is a new portable hemoglobinometer that uses disposable cuvettes to measure the total hemoglobin concentration of capillary, venous, or arterial blood. Therefore, the objectives of this study were 1) to evaluate the performance of this compact, battery-powered hemoglobinometer by assessing its precision, accuracy, and linearity, 2) to determine whether its measurements suffer from interference by hemolysis, bilirubin, fetal hemoglobin, or hemodilution, and 3) to establish whether it can easily be used by clinical personnel with little or no laboratory training. METHODS: The precision of the test instrument was assessed by making repeated measurements on blood samples. Its accuracy and linearity were evaluated by comparing its measurements with the internationally accepted cyanmethemoglobin method. Samples of whole blood with and without bilirubin, fetal hemoglobin, hemolysis, and hemodilution were also analyzed to determine if any interference occurred when these disturbances were present, and it was placed in physicians' offices to evaluate its use by non-laboratory personnel. RESULTS: Repeated measurements on blood samples with a wide range of hemoglobin concentrations were consistent with the precision specification (0.25 g/dl). The bias of the new hemoglobinometer was calculated as the mean difference between its readings and measurements with the cyanmethemoglobin method, and its accuracy as the standard deviation of the differences between the two methods. As assessed in this manner, the new hemoglobinometer had a bias of -0.04 g/dl and an accuracy of 0.40 g/dl. The linearity was checked over a hemoglobin concentration range from 0 to nearly 30 g/dl. There was a highly significant linear relationship between its readings and measurements with the cyanmethemoglobin method (slope = 0.997, y-intercept = 0.005, r = 0.999). Complete hemolysis of the sample increased the readings on average by only 0.22 g/dl. Bilirubin (17.5 mg/dl) increased the reading by an average of 0.29 g/dl, and fetal hemoglobin (76.5% HbF) reduced the readings by an average of only 0.035 g/dl. Diluting blood samples with saline also did not appreciably affect its accuracy. CONCLUSIONS: The new hemoglobinometer is fast and easy to operate. No sample preparation or pipetting is required. To operate the instrument, the user simply allows a drop of blood to fill the disposable cuvette by capillary action and inserts the cuvette into the instrument. The instrument analyzes the 10 microl sample and displays the results in less than 10 seconds. The interference caused by hemolysis, hemodilution with saline, fetal hemoglobin, and bilirubin were too small to be of any dinical importance. Tests in physician's offices indicated that clinical personnel with little or no formal laboratory training could successfully use this device. The observed precision, accuracy, linearity, and freedom from interference indicate that this hemoglobinometer is suitable for near-patient testing in a wide range of clinical settings including physicians' offices.