Methodology evaluation of a new immunoturbidimetric method for measuring serum soluble transferrin receptor.

The value of soluble transferrin receptor (sTfR) detected in serum is closely related to erythroid TfR turnover rate. An increased erythropoietic activity causes an increase in the sTfR level. Therefore, it is a useful test for monitoring the erythropoiesis. In this study, a new immunoturbidimetric method for automated measurement of sTfR was evaluated for its performance characteristics. Imprecision studies on patients' sera with 1.01 mg/l and 2.94 mg/l concentrations yielded within-run CVs of 1.16% and 1.27%. Accuracy analysis of the test by using the low and high control kit sera with 1.45 mg/l and 5.41 mg/l concentrations were 89.06% and 95.41%, respectively. The evaluation was also performed in 60 individual pediatric subjects, 30 beta-thalassemia/HbE and 30 control pediatric subjects. There is a statistically significant difference of sTfR between both groups (p < 0.0005, 95% Cl = 9.457-14.124). Ninety-five percent of matched pediatric subjects had sTfR level < or = 2.670 mg/l and 93.33% of patients diagnosed beta-thalassemia/HbE had values > 2.670 mg/l. In conclusion, this immunoturbidimeteric test yields good laboratory performance characteristics in terms of precision and accuracy.

Fast liver alkaline phosphatase isoenzyme in diagnosis of malignant biliary obstruction.

Fast liver alkaline phosphatase isoenzyme was measured by cellulose acetate electrophoresis in the sera obtained from 84 patients with specific hepatobiliary diseases and 10 control subjects. The mean value of this isoenzyme in patients with malignant extrahepatic obstruction was 130.58 +/- 107.08 U/L, significantly higher than that of patients with benign extrahepatic obstruction (65.63 +/- 34.14 U/L), as well as patients with intrahepatic cholestasis and infiltrative liver cancers (65.31 +/- 38.11 U/L and 48.47 +/- 36.85 U/L, respectively). Furthermore, we could not detect this isoenzyme in normal individuals. When 100 U/L was used as a cut-off value to discriminate between patients with malignant extrahepatic obstruction and the remaining hepatobiliary disorders, the sensitivity, specificity and accuracy of the test were 63 per cent, 84 per cent and 80 per cent, respectively. It is concluded that the fast liver isoenzyme could be a useful marker in diagnosis of malignant extrahepatic obstruction.