This study evaluated the performance of the HCG STAT Elecsys assay in 8 European laboratories using the Elecsys 2010 system. Analytical sensitivity was < 0.5 mlU/mL. The analysis of concentration series prepared by mixing serum pools with high and low HCG concentrations proved linearity up to 10.000 mIU/mL. A high-dose hook effect was not seen up to HCG concentrations of 430.000 mIU/mL. The medians of the within-run CVs (n = 21, 3 series) were 3.0% (2.1-5.8% CV; 10.4-14.4 mIU/mL), 2.4% (1.7-6.1% CV; 35.6-88.6 mIU/mL) and 2.3% (1.7-6.1% CV; 282.3-643.8 mIU/mL). The medians of the between-day imprecisions (n = 10-21) were 7.0% CV (5.2-12.0% CV; 4.0-14.0 mIU/mL), 5.5% CV (3.1-7.2% CV; 35.4-92.7% mIU/mL) and 4.1% CV (2.8-5.1% CV; 270.8-658.0 mIU/mL). The median recovery of two external quality control samples with assigned values of 9.39 and 10.40 mIU/mL) were 101.2 and 104.3% (ranges: 94.8-116.1%, 98.6-117.8%, n = 10). The assay was compared with five non-isotopic automated routine immunoassay systems (x). Slopes ranged from 0.87 to 1.15 and intercepts from-0.53 to 12.50 mIU/mL. The coefficients of correlation were with one exception (0.898) > or = 0.960. The distribution of HCG in samples from non-pregnant women and healthy men was very similar to that observed with other automated routine methods. The HCG Elecsys assay is very specific for the intact holo-hormone. Nicked HCG dimer, nicked and non-nicked beta-subunits are weakly recognised or not detected. Hemoglobin, bilirubin and lipemia (tested up to: Hb, 3.7 g/L; bilirubin, 500 mumol/L; triglyceride, 37.6 mmol/L) did not interfere the assay. The HCG Elecsys assay is well suited for the early and fast diagnosis of normal pregnancy and the detection of tubal pregnancy.

Journal Article Selectivity of enzymatic assays of sodium and potassium Get access G Steen, G Steen Search for other works by this author on: Oxford Academic Google Scholar B van Leeuwen, B van Leeuwen Search for other works by this author on: Oxford Academic Google Scholar P Langeslag, P Langeslag Search for other works by this author on: Oxford Academic Google Scholar J J van der Reijden J J van der Reijden Search for other works by this author on: Oxford Academic Google Scholar Clinical Chemistry, Volume 40, Issue 4, 1 April 1994, Pages 671–672, https://doi.org/10.1093/clinchem/40.4.671 Published: 01 April 1994

We present the results of a multicentre evaluation with Boehringer Mannheim/Hitachi instruments of new "enzymatic" methods for the determination of Na+, K+, and Cl- in serum or plasma. The between-day coefficient of variation was less than 1.4% (Na+), less than 2.6% (K+) and less than 1.7% (Cl-). The linear range of the assays were at least 80 to 200 mmol/l (Na+), 1.5 to 17 mmol/l (K+) and about 30 to at least 200 mmol/l (Cl-). The comparisons with routine flame atomic emission spectrometry and coulometry showed a satisfactory agreement of the test results. The "enzymatic" assays are insensitive to even grossly elevated levels of bilirubin and lipids (sodium, potassium, and chloride assays), NH4+ (potassium assay) and amylase (chloride assay). Interference by various drugs was not detected. Since the new methods can easily be adapted to photometric clinical chemistry instruments, they represent a valuable alternative to the use of ion-selective electrodes, flame atomic emission spectrometry and coulometry.

This enzyme immunoassay (EIA) of human prolactin (hPRL) involves incubation of sample and anti-hPRL antibodies conjugated to horseradish peroxidase (EC 1.11.1.7) in tubes coated with a second antibody to hPRL. The test can be performed within 60 min. No reaction of the antibodies with human placental lactogen and human somatotropin is detectable. The presence of detergent allows assay of both serum and plasma. Precision was improved by including polyethylene glycol in the reaction mixture. To optimize analytical recovery, we added protease inhibitor. Assay of the EIA standards shows good correlation with results for World Health Organization reference preparations. The measurable range is 1 to 400 micrograms/L. Intra- and interassay CVs are about 5%. Comparisons with two RIAs and two other EIAs show reasonably good correlations. The components of our EIA are stable for 18 months.

We evaluated a colorimetric method for the assay of uric acid in serum or urine, which utilises a Trinder chromogenic system modified by the inclusion of 2,4,6-tribromo-3-hydroxybenzoic acid for oxidative coupling to p-aminophenazone. Colour development (Amax: 512 nm) is complete within five minutes. Measurement of a sample blank is not needed. The procedure involves pre-incubation with ascorbic acid oxidase and detergent to eliminate interference by ascorbic acid and to abolish turbidity due to lipaemia; this pretreatment was effective up to 1.14 mmol/l ascorbate and up to at least 25 mmol/l triacylglycerol. Interference by icteric sera was insignificant up to about 170 mumol/l bilirubin. The method is linear up to at least 1428 mumol/l. In human serum and urine the procedure correlates well with HPLC and the uricase p-aminophenazone method on the SMAC analyser. Within-run and between-run imprecisions of the enzymic test were higher than for HPLC, but did not exceed 1.2% (CV) and 2.5% (CV), respectively.

Journal Article Individual variations of carcinoembryonic antigen (CEA) in serum of healthy subjects. Get access W Riesen, W Riesen Universität Bern, Institut für klinisch-experimentelle Tumorforschung, Tiefenauspital, Switzerland Search for other works by this author on: Oxford Academic Google Scholar A C Kessler, A C Kessler Universität Bern, Institut für klinisch-experimentelle Tumorforschung, Tiefenauspital, Switzerland Search for other works by this author on: Oxford Academic Google Scholar V Ehrhardt V Ehrhardt Universität Bern, Institut für klinisch-experimentelle Tumorforschung, Tiefenauspital, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Clinical Chemistry, Volume 33, Issue 11, 1 November 1987, Page 2123, https://doi.org/10.1093/clinchem/33.11.2123 Published: 01 November 1987