Journal of the International Federation of Clinical Chemistry最新文献

A stable calibrator, suitable for the quality control of electronic counting of erythrocytes, has been developed. The assigned concentration is determined by the cooperation of six laboratories using various types of blood cell counting instruments. The performance of the instruments was checked prior to operation. If required, corrections were applied, and deviations were taken into account. The suitability of the calibrator was tested in practice during a period of several years. The applicability of the preparation as a calibrator for use in routine practice was tested in 14 laboratories.

This study tested the hypothesis that the age of Chemstrip bG aboard ambulances is not associated with decline of accuracy. This was accomplished by removing and testing Chemstrips bG from ambulances in Salt Lake City, Utah, U.S.A. Chemstrips were developed with three concentrations of glucose (2.0, 3.8, 12.4 mmol/L; 35, 68, 223 mg/dL, respectively) in a blinded manner by three different researchers and compared with fresh controls and with the Dimension Analyzer-derived glucose. Results showed that older Chemstrips read significantly higher than fresh strips at each value of glucose tested (p less than 0.05). Increased age was associated with higher readings. Therefore, it is possible that cases of hypoglycemia may be missed by reliance on older Chemstrips. While fresh strips tended to underestimate glucose at 12.4 mmol/L, age and storage aboard ambulances tended to reverse this underestimation; older Chemstrips were associated with a more accurate reading at 12.4 mmol/L. Older age was also associated with increased standard deviation of Chemstrips. Unless this bias is considered in clinical practice, it might result in a failure to detect and treat a patient with hypoglycemia. Chemstrips aboard ambulances should be interpreted with caution when evaluating a patient on the threshold of hypoglycemia. Meanwhile, institution of a quality control program is indicated. This would include periodic testing, but might also include storage of Chemstrips, when not in use, in a climate-controlled area either on or off the ambulance.

For the laboratory control of oral anticoagulant treatment, the prothrombin time (PT) is used universally as the primary measurement. Important variability of the PT ratio (patient PT: mean health persons' PT) caused by different brands and batches of thromboplastin and instruments exists not only in North America, but throughout the world. To achieve uniformity of reporting, it is recommended that the PT ratio be transformed to the International Normalized Ratio (INR). This is possible if the thromboplastin manufacturer provides calibration data for each batch of thromboplastin. The INR scale facilitates the achievement of consensus on optimal therapeutic ranges for various clinical conditions. The INR will further improve the stability of anticoagulant treatment of travelling patients.

A glucose oxidase-H 2O 2 substrate-selective electrode (SSE) along with eight other electrodes allows the Stat Profile 5 (SP5) to measure glucose, electrolytes, blood gases, pH, and hematocrit simultaneously in whole blood. For heparinized blood gas syringe samples (n=178), orthogonal (Deming) regression showed y=0.43 + 1.00x (mmol/L), where y is whole blood glucose, and x is plasma glucose measured with the Ektachem 400 glucose oxidase slide method. For heparinized plasma (n=197), y=0.25 + 1.02x. Least squares linear regression showed y=0.25 + 1.00x (s yxx=0.49) for whole blood versus plasma, y = 0.30 + 1.01x (s yxx=0.49) for plasma versus plasma, and r=0.994 for both cases. Whole blood and plasma glucose in the same samples measured by SSE differed by less than 1%. The SP5 combines the largest number of whole blood tests currently available in a rapid response instrument well-suited for care of the critically ill patient.