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Biomedical subjects

A Uldall

Publications and source records attributed to A Uldall.

At least 19 recordsLinked to original sources
PubMed1993

A programme for assigning target values for external quality assessment schemes in countries with no authorized reference laboratories. Annex. Experiences with deviating results on Ektachem 700 XR.

The use of consensus values in external quality assessment schemes (EQAS) involves several problems and should preferably be replaced with target values obtained by methods of high metrological level. However, such values are difficult to obtain. In the present study we transferred values from the NIST (former NBS) certified reference serum SRM 909 to lyophilized and frozen test sera for various inorganic components using flame absorption or flame emission spectrometry. Enzyme values were assigned by laboratories of members of the former Scandinavian Enzyme Committee. The assignment was based on 2-4 determinations each day through 3 days of experiment. A total of 10 laboratories participated in the work. The results were utilized in a Danish EQAS. One practical concern is the fairly long time (9 months) which was needed for production, collection and compiling all data. To get an impression of how much dry chemistry analysers, e.g, could influence consensus values a Kodak Ektachem 700 XR was studied using lyophilized and frozen sera. The results are reported in the annex. On NIST SRM 909 the values found for sodium(I) were 6% too high even though the findings on frozen human sera were accurate. For aspartate aminotransferase a result three times the target values was found on a human lyophilized serum, while the values on the frozen sera only were slightly too high.

Blood↗
PubMed1993

The basis for common reference intervals for serum potassium.

In order to investigate the relevance of the currently used lower reference limit for S-Potassium in Danish hospital laboratories, analytical bias in the measurement of S-Potassium was compared with the lower reference limit in each of 52 Danish hospital laboratories. The acceptable bias range was estimated according to Gowans et al on the basis of the result of two different reference sample groups. The estimated acceptable 0.95 bias range was 0.24 mmol/L, so the observed bias range of 0.23 mmol/L was within this limit. As all preanalytical errors tend to increase the measured S-Potassium, all acceptable bias should be in the direction of decreasing the measured value. It can be concluded that analytical performance allows for more uniform (even common) reference interval(s) in all Danish and perhaps Nordic hospital laboratories, provided that preanalytical errors can be controlled.

Chemistry, Clinical↗
PubMed1993

A Nordic reference serum suitable for use as trueness control in the clinical routine laboratory.

The described reference serum is characterized by: liquid human serum at "normal" level stored in frozen state at -80 degrees C; minimum damage of proteins; aseptic preparation; cryoprecipitate and excess fibrin removed; serum cleared by ultracentrifugation; pH at 7.2-7.6; available in sealed glass ampoules with inert gas (one ml serum in each); specified components among most frequently analyzed analytes; homogeneity assured and stability monitored; produced under strict rules for good manufacturing practices (GMP). The assigned values are traceable to reference measurement procedures and reference materials of highest achievable metrological level; according to the present proposal the maximum allowable uncertainty of the assigned value is based on biological variation (shared common reference intervals); the uncertainty should ideally not exceed 1/5 of the maximum allowable bias of results obtained on patients samples (even 1/2 would theoretically be acceptable and, for a practical guide approximately < 1% may suffice). The present document provides some guidance of how the reference serum could be established in practice. The document also indicates the use of the material and further extension of the concept. The present work is done as a NORDKEM project.

Blood Chemical Analysis↗
PubMed1993

Appropriate sera for calibration and control of specific protein assays.

An ultracentrifugation technique is described which makes it possible to prepare protein calibrators and control sera which (i) are stable (more than 8 years documented for nine proteins), (ii) are clear (remains clear for more than 8 years at -80 degrees C), (iii) contain genuine proteins (documented electrophoretically and immunologically), and (iv) are reproducible to prepare (collection and preparation).

Blood↗
PubMed1993

A quality manual for the clinical laboratory including the elements of a quality system. Proposed guidelines.

Development of quality manuals is a means for the promotion of quality in clinical laboratories by describing the total quality system. It also provides opportunity of checking whether the quality system is implemented in reality and demonstrates to the hospital administration and the clinicians that the laboratory is committed to quality. The intention of these guidelines is to describe the elements of the quality system for a large clinical laboratory, and to present such a system in the form of a quality manual. The proposed guidelines comply, where relevant, with ISO/IEC guide 25 'General requirements for the technical competence of testing laboratories' and EN 45001 'General criteria for the operation of testing laboratories'. The document may be used as an aid for laboratories wishing to be accredited according to EN 45001, or intending to apply for formal certification of their quality systems, according to ISO 9001 'Quality systems--Model for quality assurance in design/development, production, installation, and servicing' utilizing ISO 9004 'Quality management and quality system elements--guidelines; Part 2 Guidelines for service'. However, information about the minimum requirements for official recognition should be obtained from the particular accreditation or certification body concerned.

Chemistry, Clinical↗
PubMed1992

[Quality assurance of results of clinical chemical analyses in Danish hospital laboratories].

During the past 35 years, voluntary professional assessment of quality of the results of analyses in Danish hospital laboratories has been undertaken under the auspices of the Danish Society of Clinical Chemistry. The analytical quality of the laboratories is described by their "imprecision" and "accuracy" as expressed by "coefficient of variation" and "bias", respectively. The participation in these programmes was 90%. During the period between 1968 and 1987, inter-laboratory variation decreased markedly where all analyses were concerned. To ensure the necessary and adequate quality, establishment of specifications of quality based on clinical/biological goals of quality has proved necessary. The commonest reasons for large imprecision and bias from the target values are less specific methods of analysis, errors in calibration and sporadic "outliers". As the result of a stable organisation for ensuring quality, Denmark is well equipped for the introduction of the great demands in documentation of quality which may be anticipated from the Common Market during the immediate future.

Chemistry Techniques, Analytical↗
PubMed1992

Reference intervals based on hospitalized 'healthy' patients and medical students in relation to analytical bias for serum potassium.

The reliability of reference intervals for measurements of serum (S)-potassium in Danish hospital laboratories was investigated (i) by estimation of reference interval based on two different, healthy subpopulations and (ii) by comparison of reference intervals for S-potassium with analytical bias in each of 52 Danish laboratories. (i) The reference values from 227 hospitalized 'healthy' patients were obtained during the period 1979 to 1987 from the first-drawn serum specimen from the hospitalized patients, who were later discharged from the hospital without a diagnosis. The estimated 0.95 reference interval was 3.34 to 4.52 mmol l-1. The other reference sample group consisted of 314 medical students from whom blood was collected in the period from 1983 to 1987. Here the estimated reference interval was from 3.44 to 4.53 mmol l-1. The concentration values from both reference sample groups were corrected for analytical bias (+0.05 mmol l-1). (ii) The 52 Danish laboratories revealed a considerable variability in reference intervals which, regarding the lower reference limit, ranged from 3.2 to 3.7 mmol l-1 in strong contrast to the analytical bias (ranging from -0.08 to +0.15 mmol l-1) in 50 laboratories (two outliers). There was no relationship between lower reference limit and analytical bias in the individual laboratories. It is concluded that analytical performance allows for more uniform (even common) reference intervals throughout the Danish and perhaps Nordic hospital laboratories.

Adolescent↗
PubMed1991

Practical aspects of internal quality assurance.

The final analytical quality of a result is influenced by external and internal factors. The quality of external elements is influenced by the individual laboratory through its choice of method and supply; such elements are, e.g. reference materials, calibrators, control materials, reagents, reagent kits, instruments and disposables. The internal elements can be described through rules for good laboratory practice (GLP), and include all aspects of internal quality assurance. In this paper, GLP is used to describe the proper milieau in which the optimally selected method is working. The control system for acceptance or rejection of any particular batch of analysis, as well as the long-term control, are also described separately.

Bias↗
PubMed1990

Quality assurance in clinical laboratories. An updated supplement to a bibliography.

A supplement to a bibliography (Scand J Clin Lab Invest 1987;47 suppl. 187:1-96) dealing with quality assurance in the clinical laboratory is presented. The increasing role of national and international standardizing bodies is stressed as well as implementation of rules of "good laboratory practice". Objectively established quality goals for all services is highly needed in order to provide a rationale for the efforts dedicated to quality improvements. Quality goals for many clinical chemistry and haematology investigations are now available.

Blood Chemical Analysis↗
PubMed1990

External quality assessment of automated blood leukocyte differential counts and other simultaneous measured quantities.

An external quality assessment scheme (EQAS) of automated differential counts of leukocytes has been carried out using selected fresh blood specimens. The measurements were carried out one day after blood drawing because of the delay in the mail. Reference laboratories established target values for differential counts. They counted visually 600-700 cells in each specimen on smears. The consensus value among 12 laboratories for manual count of total leukocytes was used as target value, but was found on average 9% smaller than the average instrumental value. H1 results compared favorable with the target value for the differentials. The less advantageous findings on Coulter S + IV are partly explained by the age of the specimen when measured. The data indicated that better calibration of the instruments could decrease the overall variation of platelets counts and haemoglobin determinations. An EQAS involving measurement on fresh specimens is in progress.

Blood Preservation↗
PubMed1990

Kits for the diagnosis of infectious mononucleosis compared with the Paul-Bunnell test.

We compared the results obtained with six different test kits for infectious mononucleosis with those obtained with the Paul-Bunnell test. The investigation was carried out in one laboratory using 149 selected pools of patient sera. Each pool was tested three times with the Paul-Bunnell test and once with each kit. The results obtained with the kits were grouped according to the titre found with the Paul-Bunnell test. The percentage of positive results within each group was calculated for each kit. The Paul-Bunnell titre, which would have classified 50% of the specimens as positive, was estimated for each kit and this was designated the 50% cut off value. In general, there was good agreement. However, false positive test results were found rather frequently with one kit (19%) and the 50% cut off values differed. One kit showed a 50% cut off value at about 8, another at about 16, and the rest at between 16 and 32. We suggest the introduction of improved internal quality control combined with external quality assessment.

Antibodies, Heterophile↗
PubMed1989

Preparation of fresh frozen human sera for external quality assessment.

A procedure for preparation of unmodified and modified fresh frozen human quality testing sera is described. The materials have been used for external quality assessment in Denmark. Examples of improvements in external quality assessment schemes using this type of material are shown.

Alanine Transaminase↗
PubMed1986

Strategies and methods for the analytical investigation of urinary calculi.

Methods for the investigation of urinary calculi are briefly reviewed. Infrared spectrometry and X-ray diffraction provide results on the actual salts, including the different degree of hydration, in contrast to wet chemistry which only measures the ions of salts. Most often the quantitated ions can, however, be combined into salts by calculation, but the different degree of hydration cannot easily be recorded by wet chemistry. Wet chemistry, infrared spectrometry and X-ray diffraction can all provide reliable results. Routine performance should be generally improved by providing quantitative instead of 'qualitative' results. In wet chemistry calculation of recovery should be obligatory. Spectra covering 4000-400 cm-1 and probably also objective evaluation are important fields for improving infrared spectrometry. A laboratory service based on X-ray diffraction or infrared spectrometry should be available for laboratories using wet chemistry to investigate rare calculi. The results should preferably be given in molar units in accordance with IFCC recommendations. Names of components should conform to the IUPAC-nomenclature and trivial names should be avoided.

Humans↗