A multicenter evaluation of the Boehringer Mannheim/Hitachi 717 system.

Analytical performance of the Boehringer Mannheim/Hitachi 717 system was evaluated in a multicenter study involving seven different laboratories. Fifty-five methods including end point chemistries, enzymes, ISE, TDM, DAU, and specific protein assays were assessed over a 7 month period. Methods on the analyzer exhibited excellent precision with CVs less than 2% for within run precision, and CVs less than 3% for between day precision for most analytes; linearity, which met or exceeded manufacturer's claims; minimal sample and reagent carryover, and no significant interference from hemolysis; icterus; and lipemia. Recovery of the assigned value for 10 analytes in SRM 909 was acceptable. Comparison of methods with other BM/Hitachi analyzers resulted in slopes close to unity (0.93-1.06); comparison to other clinical chemistry analyzers yielded slopes of 0.88-1.07. Excellent performance and diverse method applications make the BM/Hitachi 717 analyzer a suitable instrument for work station consolidation.

A multicenter evaluation of the Boehringer Mannheim ES 300 immunoassay system.

The ES 300 system, a fully automated multichannel immunoassay analyzer, was evaluated simultaneously for 9 weeks in four major centers. Precision, accuracy, carryover, comparison to in-house methods, and interferences were assessed for the following 17 tests: T4, T3, FT4, TSH, TBK, TBG, LH, FSH, prolactin, HCG, digoxin, cortisol, ferritin, IgE, insulin, AFP, and CEA. All centers reported good intra-lab and inter-lab precision. Accuracy was judged to be good based on correlation with in-house methods and recovery of target values in commercial and proficiency control materials. Linearity was evaluated for 14 analytes. Method biases were observed for T3 and insulin that were attributed to differences in standardization. No significant interferences from bilirubin, lipemia, and hemolysis were observed for all methods except insulin and AFP. Featuring random access capability, low daily maintenance, and high throughput, the ES 300 system performed well and met the stated claims of the manufacturer.

Detection of cholinesterase inhibition. The significance of cholinesterase measurements.

Human cholinesterase exists in two forms--acetylcholinesterase located in tissue microsomes and red blood cells and serum cholinesterase found in serum or plasma. The two enzymes display marked differences in structure, substrate specificity, biological function, and origin. Contemporary methods employ acylthiocholine as substrate for serum cholinesterase and a second coupled reaction of thiocholine and chromogenic disulfide agents. Clinical applications are primarily centered on subnormal levels of enzyme activity. The decreased activity levels can be caused by inhibitors, reduced biosynthesis, or dysfunctional genetic variants. Changes in enzyme activity should be related to baseline levels because there is wide individual variation as well as methodological variation. Once baseline levels have been established, cholinesterase activity becomes a sensitive indicator of pesticide intoxication and hepatic biosynthetic capacity. A more sophisticated assay, performed in the presence of an inhibitor, is required to detect the atypical genetic variants of serum or plasma cholinesterase.

Automated determination of human choriogonadotropin by use of microparticle capture analysis.

We evaluated a new microparticle enzyme immunoassay (MEIA) for human choriogonadotropin (hCG) in serum. This hCG assay is fully automated for the Abbott "IMx System," which has a dynamic range extending to 100,000 int. units/L. We tested 321 patients' sera, with hCG values ranging between 0 and 196,000 int. units/L by both the IMx hCG (y) and the Hybritech Tandem-E hCG (x) assays. Results correlated well (r = 0.972, slope = 0.87, y-intercept = 0.7). The IMx hCG assay is sensitive (0.21 int. units/L) and precise (CVs 2.4-8.7% for various hCG concentrations). No carryover to subsequent specimens was observed when specimens with values up to 10(6) int. units/L were tested, nor was any high-dose "hook" effect noted. The IMx hCG assay, which is specific for intact hCG molecules, is rapid (one to six samples in 17 min) and is a valid automated alternative to enzymatic and radioisotopic methodologies.