A. Uldall

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.

A wet chemistry method for the analysis of urinary calculi

A procedure for the routine investigation of urinary calculi is described. The investigation scheme was based on existing methods in the routine laboratory for calcium(II), magnesium(II), phosphate and urate in serum. The substance content of oxalate was calculated as non-phosphate-bound calcium(II). Furthermore the test for cystine in urine was utilized. Two specially designed tests were used, one for carbonate apatite and one for verification of the presence of oxalate. The scheme was applied to 30 specimens of human origin. The sum of the mass fractions of identified and calculated components in the calculi was found to be 0.88 on the average (s = 0.05). Low values for this sum may serve as an indication of the presence of rare components that are not included in this analytical programme. A few calculi containing rare components required special methods for the investigation and are most conveniently investigated in a specialized laboratory using X-ray diffraction or infra-red spectrometry. In this paper, however, we describe wet chemistry methods, suitable for reliable cystine determinations and for oxalate in calculi containing, for example, brushite, where the calculated oxalate value is uncertain. These methods may be used as an alternative to the physical methods for many of the rare calculi.

Preparation of frozen reference sera and examples of applications

We describe procedures for preparation of human serum from ACD bank blood and bovine serum from slaughter house blood. Preparation techniques including filtration and dialysis are described in detail as well as how to obtain desired concentrations. Special attention has been drawn to procedures yielding low lactate dehydrogenase activity. Long-term storage should take place at -75 degrees C. Different frozen reference sera have been used for calibration purposes, internal quality control and external quality assessment.

Measurement of ionized calcium with five types of instruments. An external quality assessment

An external quality assessment for ionized calcium determinations was carried out in 24 laboratories in Northern Europe. Both protein-free and protein-containing test materials were included in the study. The average within-laboratory variation (CV) for all test materials was 3.1, 1.7, 1.2, 1.8 and 1.3% for the AVL 980 (AVL, Graz, Austria), the Microlyte (Kone, Espoo, Finland), the Nova 2 (Nova Biomedical, Newton, Ma USA), the Orion SS-20 (Orion, Cambridge, Mass., USA), and the ICA1 (Radiometer, Copenhagen, Denmark) respectively. The corresponding interlaboratory CV was 3.1, 2.9, 3.1 and 2.4%. The variation between types of instruments was even larger and caused differences of up to 33%. The results indicate a need for well-defined protein-containing control material.

2.2. Present analytical quality in the nordic clinical chemistry laboratories

An introductory review is given of the discussion in the Nordic countries on the definition, aim, and optimal organization of quality control. Published and unpublished Scandinavian works have been reviewed and commented under the following headlines: common chemical analyses, enzyme analyses, serum and plasma protein analyses, hormone analyses, drug analyses, hematological tests, and urine analyses. It is concluded that methods for calculating medical standards of analytical quality in clinical chemistry form the logical background for the design of an optimal quality control system, which will guarantee that analytical results well have a specified probability of satisfying the medical requirements.

Quality assurance within clinical chemistry—a brief review emphasizing ‘good laboratory practice’

Goals for analytical quality within clinical chemistry should be recognized in order to select proper analytical methods including internal quality control systems, which in principle could guarantee the analytical quality. However, such an ideal scheme is only successful if the whole analytical milieu is well functioning. This can be achieved by following rules of good laboratory practice (GLP). Good laboratory practice includes among other things laboratory management, organization and education of the staff, written instructions for all laboratory procedures, regular check of instruments, reagents and utensils, careful laboratory work, proper reports to the clinician and discussions with the clinician whether the laboratory service is sufficient, for example, in relation to the analytical repertoire and the reporting time. Development of better calibration and quality testing materials is essential to improve quality. More elaborate external quality assessment programmes, which should also cover a much...

Visual tests for urinary amylase investigated in the routine laboratory

Ninety-seven fresh urine specimens were tested in the routine laboratory with the Rapignost Amylase test strip, and the results were compared to those obtained using Phadebas Amylase test tablets to investigate the transferability of the results obtained by the Rapignost method to those of the Phadebas method under routine conditions. The fraction of conflicting negative results of Phadebas-positive specimens was 9% and the corresponding fraction of conflicting positive results was 13%. An attempt to improve the transferability by changing the comparison scale slightly did not succeed. However, a visual binary test based on 180 s incubation at 37 degrees C of 400 microliters urine in a suspension of a Phadebas Amylase test tablet seemed more suitable in selection of specimens with Phadebas amylase activity less than 2000 U/l (upper limit of the reference interval). These specimens amounted to approximately 75% of all amylase specimens in our laboratory.

Inter-laboratory comparison of acid-base variables in human blood and in quality control materials

Routine results, pH, partial pressure of carbon dioxide (pCO2) and of oxygen (pO2), and standard hydrogen carbonate ion concentration (SBC) in identical specimens of arterial blood from patients deviate substantially. The results from seven laboratories (each laboratory examining the same 12 patients and the same five types of quality control materials) and evaluation in terms of accuracy and precision suggest the variations between days (delta 2) and single measurements (sigma 2) to be the main factors for these deviations. A reduction of these variations must have the highest priority in quality control programmes, since the variations mask possible true level deviations between laboratories. The five control materials (Qualicheck, Quantra whole blood level I-II-III and hemolyzed donor blood) are not fully optimal as substitutes for patient blood in such quality control programmes.