Multicentre evaluation of the Boehringer Mannheim/Hitachi 717 analysis system.

We conducted an European multicentre trial to assess the performance of the new Boehringer Mannheim/Hitachi 717 analysis system. The photometer response was linear up to an absorbance of 2.8. The maximal CV of photometric imprecision was 0.5% for the wavelength pair 340/405 nm within the absorbance range 0.9 to 2.4. For the 13 analytes in our study, mean within-run imprecision was less than 2%, and mean between-day imprecision less than 2.5%. The results obtained with the Hitachi 717 instrument correlated closely with those of comparison instruments. Linearity for the various tests was high and exceeded the manufacturer's claims. No drift was detected during an 8-hour work period; carry over could not be detected under the chosen experimental conditions. The new instrument was readily accepted by the evaluators because of its ease of handling and simple daily maintenance.

Demonstration of a combined deficiency of xanthine oxidase and aldehyde oxidase in xanthinuric patients not forming oxipurinol.

Genetic heterogeneity has been suggested in xanthinuria from the hitherto unexplained ability of some patients with this hereditary disorder to convert allopurinol to its active metabolite oxipurinol--an activity generally attributed to xanthine oxidase. This study provides evidence that the enzyme aldehyde oxidase is also deficient in xanthinuric patients not converting allopurinol to oxipurinol, whereas a xanthinuric patient with normal formation of oxipurinol had normal aldehyde oxidase activity. It is concluded that the enzyme aldehyde oxidase is the principal enzyme responsible for the formation of oxipurinol in man.

Isocratic ion-pair high-performance liquid chromatographic methods for the determination of uroporphyrin and coproporphyrin type II and IV isomers in human urine.

Urinary porphyrins of porphyric patients were isolated as their methyl esters by using a simple, modified thin-layer chromatographic system. Existing methods for the isocratic ion-pair high-performance liquid chromatographic separation of uroporphyrin and coproporphyrin isomers were decisively improved by elevating the column temperatures, changing the types of columns used and modifying the eluent compositions. These techniques were applied to the determination of the isomeric distribution of uroporphyrins and coproporphyrins isolated from urines of patients in the acute or latent phase of acute intermittent porphyria. In these urines relatively high contents of the atypical uroporphyrins II (2-5%) and IV (13-19%) were found. The coproporphyrin fractions contained significantly smaller amounts of the atypical isomers II (1-2%) and IV (2-5%), the presence of which was demonstrated for the first time in such urines. Several mechanisms for the formation of the atypical coproporphyrin isomers are discussed. The isocratic ion-pair separation method served also to control the isomeric purity of uroporphyrin specimens of both natural and synthetic origin.

Digitalis intoxication and treatment with digoxin antibody fragments in renal failure.

Severe digitalis intoxication today is preferentially treated by intravenous infusion of Fab fragments of digoxin antibodies (Digitalis Antidot BM). The kinetics of Fab fragments in the circulation are well known when kidney function is normal or slightly impaired. There are no data available, however, in complete renal failure. We observed a patient with life-threatening digitalis intoxication (serum digoxin, 3.7 ng/ml) and anuria, who was treated successfully by 160 mg Fab fragments i.v. Serum digoxin and Fab fragment concentrations could be followed for 229 h. The extrarenal clearance of Fab fragments was lower (5.6 ml/min) than in patients with normal kidney function (10.9 ml/min). This finding suggests that lower doses than usual might be sufficient for treating patients with severe digitalis intoxication and renal failure.

Evaluation of a new chemiluminescence immunoassay for the determination of human chorionic gonadotropin in serum.

A new commercially available chemiluminescence immunoassay for the quantitative measurement of human chorionic gonadotropin and its beta-subunit in serum was compared with the enzyme immunoassay used in our routine laboratory. Human chorionic gonadotropin was determined in serum from pregnant women, as well as from women with abortus imminens, suspected ectopic pregnancies or with molar pregnancies. The new human chorionic gonadotropin assay was also evaluated in combination with an automatic sample processor for distributing samples to the antibody-coated wells of the microtitre plates. The analytical precision, specificity and accuracy of the human chorionic gonadotropin assay were assessed with 152 sera, using the 60 min-incubation as well as the shorter 15 min version. Specificity was comparable with the conventional system, whereas the chemiluminescence assay performed better with respect to the assay detection limit and measuring range. The enhanced chemiluminescence system for the determination of human chorionic gonadotropin is an efficient assay which agrees well with our routine assay. In connection with an automatic sample processor it enables an advanced and versatile system for the determination of human chorionic gonadotropin in laboratories with large series. The system is rapid, easy to handle and apparently free from interference.

Detection of non-typical porphyrin isomers in human urines by ion-pair reversed-phase high-performance liquid chromatography.

An improved ion-pair reversed-phase high-performance liquid chromatographic system has been developed for the separation of uroporphyrin isomers I, II and III, whereas the isomers III and IV could not be resolved. Application of this method to the analysis of urines from porphyric patients indicated the presence of small amounts of the non-typical uroporphyrin isomer II. The questionable presence of the isomer IV was confirmed by acid-catalyzed decarboxylation to the corresponding coproporphyrin isomers, which were completely separated by a modified ion-pair method at elevated column temperatures. These procedures enabled the detection of small fractions of the atypical isomers II (1-3%) and IV (8-15%) besides the normal isomers I and III in urines of patients suffering from attacks of acute intermittent porphyria. Because such urines contain large amounts of porphobilinogen, the nonenzymatic self-condensation of porphobilinogen to uroporphyrinogens was studied under mild reaction conditions. In these experiments quite similar isomeric compositions were observed as compared to those in urines of patients with acute intermittent porphyria. Thus the non-typical uroporphyrin isomers II and IV present in human urines originate from a simple non-enzymatic condensation of porphobilinogen.

Investigation of the performance of the ES 600 Enzymun-Test system. A multicentre study.

The ES 600 sample-selective multibatch analyser was subjected to a multicentre evaluation in six laboratories in accordance with ECCLS guide-lines. During the 3-month trial, five Enzymun-Test diagnostics (T4, TBG, Digoxin, CEA and TSH)1) were measured at 25 degrees C. The study yielded the following results: 1. The within-series and between-series precision were very good, with mean CV's of approx. 3% and 7% respectively. 2. Recovery of the target values for three control sera was in the range +/- 5%. 3. A trend in measurements did not occur in any of the methods investigated (for series of over 240 determinations). 4. Comparison of the results with those obtained on the ES 22 Enzymun-Test system showed good agreement. 5. Within the measuring range defined by the standards, no deviations could be ascertained upon dilution of the samples. 6. Total carry-over in the instrument was below 0.05%. From studies with instruments from the first production series, it became evident that modifications were necessary to improve the reliability. A follow-up measuring programme confirmed a clear improvement in reliability and a reduction in the imprecision, particularly for results from series to series.

A multicentre evaluation of the Boehringer Mannheim/Hitachi 704 analysis system.

The selective multitest Boehringer Mannheim/Hitachi 704 analysis system was examined according to the ECCLS guidelines in a multicentre evaluation involving four laboratories. Ten routine parameters, covering most of the application settings of the instrument, were measured in the respective laboratory at temperatures 25, 30 or 37 degrees C. The trial lasted four months and gave more than 40,000 data. It yielded the following results: 1. Within the four laboratories the mean coefficients of variation for three control sera at different concentrations were found to be equal to or better than 1.6% for the within-run imprecision and 2.8% or better for the between-day imprecision. 2. No drift was observed during eight hours. 3. Because of the high linear measuring range a re-run analysis was seldom necessary. 4. Sample-related carry-over was not seen. Reagent-dependent carry-over was measured from cholesterol to uric acid and from triacylglycerols to lipase. Through modification of the cholesterol and triacylglycerol reagents, the carry-over effect was practically eliminated. 5. The recovery of the assigned values of control sera showed average values between 99 and 104%. For bilirubin, creatinine, creatine kinase and alanine aminotransferase some control sera showed deviations greater than 10%. 6. In all cases, regression analysis of the results obtained in comparisons of the present instrument with the Hitachi 705 or 737 yielded slopes close to unity with extreme values of 0.95 and 1.06. 7. During the entire evaluation period there was no malfunction or breakdown of the instruments. The evaluators came to the conclusion that the analytical performance as well as the reliability and practicability of the Hitachi 704 can be rated as excellent.

Analytical performance of the random access analyser Hitachi 737. A multicentre evaluation.

The selective multitest analyser Hitachi 737 was examined according to the ECCLS guidelines in a multicentre evaluation involving 4 laboratories. Twenty routine parameters, including the electrolytes, sodium, potassium and chloride, were measured at 37 degrees C. All of the measured values were included for evaluation without correcting for outliers. The trial, which lasted 4 months and involved over 70 000 analyses, basically yielded the following results: The precision can be termed very good. For the majority of the methods, the day-to-day coefficients of variation were below 2%. The highest coefficient of variation was 6.3% (for creatine kinase) and the lowest below 0.1% (for gamma-glutamyltransferase). The recovery of the assigned values of control sera was very good for most of the parameters (between 95% and 105%). Only with bilirubin, phosphate and chloride did greater deviations occur in a few control sera. Excellent agreement was found between the results obtained from the instruments used in the comparison: the Hitachi 705, a flame photometer and a chloride meter. No drift effects were observed. The same applied to carryover effects, provided that Boehringer Mannheim's recommendations concerning method combinations are observed. Because of the large measuring range, it is necessary to repeat analyses only in exceptional cases. During the entire period of the trial there were no stoppages due to the instrument malfunction. As a result of its reliability, the Hitachi 737 is well suited for routine operation and emergency analysis in medium to large-sized laboratories.

[Immunophenotyping of lymphocyte subpopulations using monoclonal antibodies in an analytical flow cytometer: evaluation of the method and reference values]. / Immunphänotypisierung von Lymphocyten-Subpopulationen mit monoklonalen Antikörpern im analytischen Durchflusscytometer: Evaluierung von Methodik und Referenzbereichen.

Analytical flow cytometers which are easy to operate, and monoclonal antibodies specific for cell surface determinants of lymphocytes, offer a simple and rapid method for the identification of the immunological phenotype of lymphocyte subsets. We investigated mononuclear cells isolated from EDTA-blood bv density gradient centrifugation. The intraassay precision (n = 12) of the determination by means of monoclonal antibodies directed against T-cells (Leu 4), T-helper/inducer-cells (Leu 3 a, b), T-suppressor/cytotoxic cells (Leu 2 a) and cells of the 'NK'-phenotype (Leu 7) varied between 2.2 and 7.9%. Studies using the subset markers Leu 2a and Leu 3a, b conjugated either to fluorescein isothiocyanate (FITC) or to phycoerythrin (PE) showed comparable results for both subsets. Dual immunofluorescent analysis using two different antibodies conjugated to contrasting fluorochromes resulted in slightly higher fractions of T-helper/inducer-cells (Leu 3a, b-FITC: a = 0.97, b = 3.18, r = 0.98) and T-suppressor/cytotoxic cells (Leu 2 a-PE: a = 0.99, b = 2.22, r = 0.97) compared with single immunofluorescent analysis. We found no constant association to explain this statistically significant discrepancy (p less than or equal to 0.0002). The investigation of 100 controls established the following reference values for the fraction of lymphocyte subsets (median, 95%-interval): T-cells 0.75 (0.57-0.87), T-helper/inducer-cells 0.47 (0.34-0.63), T-suppressor/cytotoxic cells 0.26 (0.15-0.42), 'NK'-cells 0.16 (0.04-0.34). The corresponding absolute numbers of cells are: T-cells 1.300 (0.730-2.240), T-helper/inducer-cells 0.820 (0.44-1.540), T-suppressor/cytotoxic cells 0.450 (0.190-0.915), 'NK'-cells 0.300 (0.060-0.670).

[Computer-assisted findings on protein electrophoresis on cellulose acetate film]. / Rechnerunterstützte Befundung von Eiweisselektrophoresen auf Celluloseacetatfolie.

Until a short time ago efficient computer assisted reporting of electrophoretograms was not possible owing to the lack of appropriate technology. By integrating a fully mechanized electrophoresis system into the laboratory data processing system of a centralized institute of clinical chemistry, the separation and the interpretation of results can be performed for 300 samples per day. The interpretation is based upon available patient data (specified clinical diagnoses, previous results), calculated fractions and analysis of the electrophoretic curve in the area of albumin and the beta- and gamma-globulin fraction. In this way it is possible to classify hereditary bisalbuminaemias and to detect transient bisalbuminaemias and monoclonal gammopathies. Diagnostic indications of specific dysproteinaemias and defect proteinaemias are printed on the report form if individual serum protein fractions and the total protein content are changed specifically. The results of the different electrophoretic fractions, the total protein and a set of possible alterations of the curve are numerically coded according to the scaled biochemical ranges in five definite sections or to a decision matrix (alteration 'given' or 'not given'), respectively. The composed 'result patterns' are matched with preassigned 'reference patterns' stored in the computer file. The procedure is efficient and adaptable to other areas of analysis.

A data processing system adapted to the special needs of the emergency laboratory.

A data processing system for the emergency laboratory was integrated in our clinical laboratory computer system, its prime objective being the service requirements of the laboratory. It included the possibility of simultaneous optical reading of request forms and on-line capturing, processing, and printing of laboratory test data. Priority request forms, which allow the clinician to specify the interval by which emergency test results must be available, are registered by an optical reader and arranged according to urgency by the computer. The production of worksheets is replaced by visual display of information required for accurate specimen analyses on a large colour TV screen. The individual processing status of all tests from as many as 30 request forms is displayed in a colour code. For process control the updated delay time for test performance is faded in. All reports are produced by direct machine transfer of verified test results. For security purposes all steps of sample processing (request, result, report) are recorded via line printers outside the emergency laboratory. The capacity of the computer for managing sample and data processing reduces the work load for technicians. This results in a reduction of the turn-round time of tests. 95% of all requested tests are performed and reported within the requested time period and in emergencies, test results are available within 5-10 min. There has been no major breakdown of the system in over one year of use.

[Optimization of sample splitting in a centralized clinical chemical institute (author's transl)]. / Optimierung der Probenverteilung in einem zentralisierten klinischen-chemischen Institut.

Mechanized sample splitting machines controlled by a laboratory data processing system have been realized in only a few centralized laboratories. Bottlenecks and mistakes in sample processing are avoided by means of direct machine readable identification and parallel splitting of the secondary tubes. Our previous experience has shown that a strategy for sample splitting has to go far beyond these basic functional requirements. The splitting process must be suited to the organization of the particular laboratory, and it must be adjusted to deal with problems of individual samples containing analytically interfering substances, or variable splitting may be required in cases of inadequate sample volumes. In addition to sample identification, the secondary tube has to be coded with the date and the type of material. This allows cumulative on-line processing and series of analyses of different materials. A suitable positional arrangement of containers for control material must be born in mind for quality control performances. We have realized these additional requirements by means of a consequent mutual adaptation in the layout of the request form (marking of priority and additional information), the file structure of the data processing system and the control program of the sample splitting machine.

Analysis of free stool porphyrins by high-performance liquid chromatography.

The determination of stool porphyrins is necessary for the diagnosis of some porphyrias in clinical laboratories. Quantitative methods for the analysis of faeces for porphyrins are unpleasant and difficult to perform. An extraction and ion-pair reversed-phase high-performance liquid chromatographic procedure is described for the separation and determination of individual free stool porphyrins. The within-assay coefficients of variation range from 2 to 6%. A linear response curve is observed between 38 and 380 nmol/g for coproporphyrin I in dry stool The method can be applied to the routine analysis of free stool porphyrins in the clinical laboratory.