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A Scholer

Publications and source records attributed to A Scholer.

At least 19 recordsLinked to original sources
PubMed1997

Comparability of a new turbidimetric digoxin test with other immunochemical tests and with HPLC--a multicenter evaluation.

A new turbidimetric inhibition immunoassay for digoxin (Tina-quant [a] Digoxin, Boehringer Mannheim) was evaluated in seven laboratories. It can be performed without sample pretreatment with ready-to-use reagents on nondedicated analyzers in combination with routine clinical chemistry. The studies revealed a good analytical performance: lower limit of detection 0.12 microg/L (3 SD from mean of blank); linearity up to 7.5 microg/L; median between-run CVs 8.1% (0.6 microg/L), 2.8% (1.5 microg/L), 1.9% (3 microg/L); mean analytical recovery in control sera 98-102%; slopes from 0.97 to 1.09 and intercepts from -0.28 to 0.10 microg/L in comparison with four immunoassays; and a high resistance to common interferents. The test was more resistant to digoxin-like immunoreactive factor (DLIF) interference than other methods, showing cross-reactivity only in some intensive care patient samples. Among 192 patients in whom DLIF is expected (e.g., pregnant women, patients with renal failure, newborns), 90% of results were < or =0.26 microg/L digoxin. Cortisol showed no cross-reactivity and digoxigenin had a low reactivity. An interlaboratory survey revealed a good comparability of the Tina-quant [a] test with the median of all methods (slope 0.99, intercept -0.06 microg/L). An HPLC method for digoxin based on isocratic separation of samples on an RP-18 column followed by detection by an immunoassay yielded a reasonable comparability with the immunochemical tests with noncritical samples. Divergent results of immunoassays caused by DLIFs or different cross-reactivities with digoxin metabolites or derivatives can be explained by the use of this HPLC method.

Anticoagulants↗
PubMed1997

European multicentre evaluation of the analytical performance of the Abbott AxSYM Abused Drugs Assays.

In accordance with the guidelines of the European Committee for Clinical Laboratory Standards (ECCLS), the performance of the Abbott AxSYM Abused Drugs assays were evaluated and compared with the results provided by the following systems: Syva Emit d.a.u./Roche Cobas Mira S Plus, Abbott TDx and ADx, Syva Emit d.a.u./Syva ETS Plus, Syva Emit II/Hitachi 717 and Roche Abuscreen OnLine/Roche Cobas Mira S Plus. The test analytes, cannabinoids, cocaine metabolites, opiates, benzodiazepines and barbiturates, were each investigated in three laboratories on different systems. The imprecision of all systems in the series and from day to day was good, with CVs less than 5% or 10%, respectively. The AxSYM calibration curves were stable for 3-4 months and none of the systems displayed any shift in the results of the analyses within one day or any faults caused by sample contamination. Within the framework of this study, a total of 1860 urine samples were investigated; 741 results were positive. All results which remained discrepant between AxSYM and the comparison systems after repeated analysis (n = 17) were subjected to further investigation using a reference method, with the exception of one barbiturate and two benzodiazepine samples. An additional test criterion was the practicability of the systems investigated and the versatility of the software. During this evaluation, the results provided by the Abbott AxSYM were excellent and were fully in line with the manufacturer's claims. The reliability of the FPIA technology that has been the subject of frequent investigation was also convincing during this evaluation. The possibility of semi-quantitative determination, the stability of the calibration curves, the ability to process an emergency sample without delay and its high suitability to routine operations are the convincing benefits offered by this system.

Calibration↗
PubMed1993

Assessment of lidocaine metabolite formation in comparison with other quantitative liver function tests.

In clinical practice, the seriousness of liver disease is assessed based on the combined information from clinical examination, routine biochemical tests, and liver histology. Recently, the assessment of hepatic lidocaine metabolism has been proposed as a quantitative liver function test offering valuable additional information. To evaluate whether this new liver function test reflects the combined clinical assessment, we prospectively measured lidocaine metabolism in 111 patients with well characterized liver disease. In addition, lidocaine test results were compared with the aminopyrine breath test and the galactose elimination capacity. Lidocaine (1 mg/kg) was injected i.v. and serum concentrations of its main metabolite monoethylglycinexylidide were determined after 15 min. The results varied widely and the means (+/- S.D.) were similar among patients with mild liver disease (46 +/- 23 ng/ml), but significantly (P < 0.05) lower among patients with Child class A cirrhosis (19 +/- 11 ng/ml) or Child class B or C cirrhosis (21 +/- 19 ng/ml). The [13C]aminopyrine breath test, however, gave a better discrimination among patients with increasing severity of liver disease than lidocaine metabolite formation. The galactose elimination capacity finally best separated patients with mild liver disease from those with cirrhosis. The correlations between any two of the different quantitative liver function tests were weak (R2 consistently < 0.2). We conclude that lidocaine metabolite formation, like other quantitative liver function tests that are based on the microsomal metabolism of model compounds, quantitates a very particular enzymatic reaction which may not be representative for the functional reserve of the entire organ.

Adolescent↗
PubMed1987

Computer-assisted individualized lidocaine dosage: clinical evaluation and comparison with physician performance.

The performance of a computerized dosing aid in achieving a target serum concentration of lidocaine in the middle of the recommended therapeutic range (3.5 mg/L) was evaluated in 63 patients treated for acute ventricular arrhythmias. In all patients a serum concentration measurement was obtained shortly after starting lidocaine infusion. In 22 patients a microcomputer program based on a Bayesian forecasting technique was used for dosing recommendations, whereas in 41 the serum concentration was interpreted and the dose was adjusted by the unaided physician. Both groups were similar with respect to the average concentration achieved (control: 3.8 +/- 1.13 [SD] mg/L, computer-aided: 3.5 +/- 0.59 mg/L). However, the interindividual variability was significantly larger in the control group (95% confidence interval: 1.5 to 6.1 mg/L vs 2.3 to 4.7 mg/L [p less than 0.01]). Nine of the 41 patients in the control group had a lidocaine concentration outside the recommended therapeutic range of 2 to 5 mg/L compared to only 1 of 22 in the computer-aided group. Lidocaine concentrations greater than 2 mg/L were associated with significantly more effective suppression of ventricular arrhythmias (p less than 0.05). The results show that Bayesian forecasting outperforms the physician in early adjustment of lidocaine dosage based on serum concentration measurements.

Aged↗
PubMed1985

Continuous-flow analysis for glucose with use of glucose dehydrogenase immobilized in glass tubes.

We describe a method for determining glucose in serum with glucose dehydrogenase immobilized on the inner walls of glass tubes. The reactor was incorporated into a channel of a continuous-flow analyzer (the Technicon SMAC) and used daily for four weeks in routine analysis for serum glucose. During this period we tested the linearity, precision, accuracy, and durability of the reactor. Results correlated well (r = 0.9949) with those obtained by routine methods with free (nonimmobilized) glucose dehydrogenase. The method is shown to be practicable for use in the routine laboratory.

Autoanalysis↗
PubMed1984

Evaluation of a colorimetric test for the determination of alpha-amylase with p-nitrophenylheptaoside as substrate.

A continuous method for the determination of alpha-amylase activity with a defined substrate has been published by Rauscher et al. in Berichte der Osterreichischen Gesellschaft für Klinische Chemie 4, 150 (1981). It offers the following advantages: good practicability, easy adaptation to analysers and short incubation time. Twenty-one laboratories took part in a multicentric study on this method, working with different instruments and manual procedures at three temperatures. Additionally, all laboratories participated in a laboratory improvement program, in order to discriminate systematic from accidental errors. Data on imprecision, linearity, interferences and comparability of the method have been presented at a workshop. The resulting coefficients of variation for imprecision in series as well as from day to day were 0.6-6.3% and 1.3-7.7%, respectively. No interferences from bilirubin, glucose, maltose and 37 selected drugs were found. The results from the described method correlate well with those from an UV-test (substrate: maltoheptaose); compared with other methods, however, the expected systematic deviations were observed. Reference values for 25, 30 and 37 degrees C are indicated in this report.

Colorimetry↗
PubMed1983

[Diagnostic value of the determination of serum amylase and serum lipase in suspected acute onset of acute or chronic pancreatitis].

In a prospective study the value of serum amylase and serum lipase determination has been analyzed in 19 patients with an acute episode of acute or chronic pancreatitis and in 19 patients with acute abdomen not due to pancreatitis. The concentration of urinary amylase and the urinary output of amylase in the spot urine as well as after a two-hour collection period have also been examined. The normal values were determined in 21 healthy volunteers and the reproducibility of the various parameters was analyzed after 1 hour and 25 hours in these volunteers. For diagnosis of an acute episode of chronic pancreatitis serum amylase was found to have good sensitivity, but a specificity inferior to that of serum lipase. By contrast, the specificity of serum lipase is excellent. Unlike determination of serum enzymes, measurement of urinary enzymes in all variations does not offer any further advantage. Except for the combination of serum amylase and serum lipase, none of the other tested combinations provides further diagnostic information. The examination of spot urine samples is not inferior to the 2-hour urine specimen. For the time being the combination of serum amylase and serum lipase determination is again recommended for diagnostic routine in patients with an acute episode of pancreatitis.

Abdomen, Acute↗
PubMed1982

[Clinical relevance of N-acetylglucosaminidase determination in urine of kidney transplant recipients with and without cyclosporin A].

From January to September 1981 urinary gamma-N-acetyl-glucosaminidase (NAG) excretion was measured in 23 cadaver kidney recipients up to 90 days posttransplant. Conventional immunosuppression with azathioprine and prednisone was used in 12 patients, and cyclosporin A (CyA) in 11 patients. The purpose of this study was to assess the clinical value of NAG determinations in the diagnosis of acute rejection episodes and CyA-induced nephrotoxicity. A total of 26 acute rejection episodes were observed. 14 (54%) of these were associated with a significant increase in NAG excretion. The other 46 episodes of increased NAG excretion (77% of a total of 60 episodes) were unrelated to acute rejection reactions. No obvious reason was apparent in 39 instances (63%). Nine out of 11 patients treated with CyA showed one or more increases in NAG excretion, but the number of such episodes did not differ between patients with CyA serum concentrations below 500 ng/ml and those with levels above 500 ng/ml. Histological signs of CyA toxicity in graft biopsies correlated well with increased NAG excretion. It is concluded that increases in NAG excretion are not sensitive and specific enough to be of definite help in the diagnosis of acute rejection and/or CyA-induced nephrotoxicity.

Acetylglucosaminidase↗
PubMed1982

[Creatine kinase (CK) activity and its isoenzyme MB in the serum of randomly selected patients without acute coronary disease].

Elevations of creatine kinase (CK) are not specific for myocardial disease. However, enzyme release due to extracardial factors is not necessarily comparable in healthy and diseased persons. It is therefore questionable whether normal values obtained in a group of healthy or mildly ill subjects are also valid for severely ill patients. The activity pattern of CK and its isoenzyme MB was therefore examined in the serum of 100 consecutive patients attending the medical outpatient clinic and of 170 patients at the time of admission to the medical emergency ward. The clinical and laboratory findings and diagnoses for all patients are recorded. Acute coronary disease was excluded. Determination of CK was performed according to the method described by Oliver [21] and Preston [27], but the results were calculated for a reaction temperature of 30 degrees C and determination of CK-MB was in cue with the method described by Prellwitz [25]. 4% of the outpatients and 14% of the emergency patients had CK values of over 100 U/1. In the majority of the patients (19 of 28) with CK values of over 100 U/1, the history revealed that the elevated values could be attributed to skeletal muscle trauma. After these values had been excluded, the 95% percentile was 20-85 U/1 (outpatients) and 20-110 U/1 (emergency ward) for men and 15-90 U/1 (outpatients) and 20-75 U/1 (emergency ward) for women. Without this selection, the newly admitted male patients in particular would have presented considerably elevated values. Since an explanation was found for most of the elevating values, the adjusted figures show no major differences between outpatients and hospital patients. The limit for CK-MB activity indicative of cardiac origin is presumed to be between 4-10% of the total CK activity. However, individual variations are observed, since CK-MB activity in skeletal muscle in variable and atypical isoenzymes may interfere with CK-MB determination. In this study 14% of the patients admitted to the emergency ward with CK values of under 100 U/1 presented false positive CK-MB values of over 10% of the total CK activity. It is concluded that CK-MB determination using the antibody method does not afford reliable results when there is no elevation of total CK.

Adult↗
PubMed1982

Measurement of prostatic acid phosphatase in serum and bone marrow: radioimmunoassay and enzymic measurement compared.

We quantitated the concentrations of prostatic acid phosphatases (EC 3.1.3.2) in serum and bone-marrow aspirates with three commercial radioimmunoassay kits, and the catalytic activities with a thymolphthalein monophosphate-based enzyme test. The enzyme's immunological activity in serum was compared with its catalytic activity for its potential as a detector of early prostatic cancer and its performance as an early marker of metastatic activity in bone. Neither measurement is useful for detecting early stages of prostatic cancer. The spread of carcinoma to lymph nodes or to bone is detected with greater frequency by radioimmunoassay than by the enzymic test. Radioimmunoassay also detected metastasis to the bone more frequently than did physical methods. Analytical and clinical performance of the four methods is described.

Acid Phosphatase↗