Comparability of lipoprotein measurements, total:HDL cholesterol ratio and other coronary risk functions within and between laboratories in Australia.

We assessed the intralaboratory imprecision and interlaboratory comparability of lipoprotein measurements and related cardiovascular risk functions such as the total to high density lipoprotein cholesterol (TC:HDL) ratio. Analysis of 5 separate plasma pools was carried out in 4 laboratories which regularly perform lipoprotein testing. We also performed a retrospective audit on RCPA-AACB Quality Assurance Programme data from 134 laboratories participating in the Special Lipid Programme in 1991. Intralaboratory imprecision and interlaboratory comparability are reported as coefficient of variation (cv) and its 95% confidence limit. For the national data, we calculated the percentage of laboratories within specified ranges (+/- 3, 5 or 10%) about the national mean (or median) for a given level of each analyte. Intralaboratory imprecision and interlaboratory comparability amongst the 4 laboratories were close to, or within recommended limits for, TC, TG and HDL, but the interlaboratory comparability of LDL and coronary risk functions exceeded these limits. On a national level, interlaboratory comparability of TC:HDL was within +/- 5% for only 43% of laboratories, and even fewer (26%) were within this range at higher values of the ratio. We conclude that it is not possible to recommend the use of coronary risk functions at present because of sub-optimal interlaboratory comparability. Even if measures are introduced to overcome this problem, coronary risk functions may over-simplify coronary vascular disease risk in a variety of clinical situations.

Adaptation of methods for glutamate dehydrogenase and alcohol dehydrogenase activities to a centrifugal analyser: assessment of their clinical use in anoxic states of the liver.

Sensitive, precise, and rapid methods for the measurement of alcohol dehydrogenase (ADH) and glutamate dehydrogenase (GDH) were developed on the Cobas Bio centrifugal analyser. The optimal pH for ADH in caucasians was 9.8. Non-linearity of ADH enzyme activity was observed when samples were diluted in saline; linearity was restored when inactivated serum was used as diluent. ADH was shown to be a sensitive index of liver anoxia due to cardiorespiratory disturbance (clinical sensitivity 90%) and generalised anoxia. GDH exhibited sensitivity equal to that of alanine aminotransferase (ALT) but was inferior to gamma-glutamyltransferase (GGT) in the detection of specific liver disease. Both ADH and GDH were sensitive indicators of alcoholic liver disease.

Performance of quantitative urine analysis in Australasia critically assessed.

The standard of quantitative urine analysis in Australasia has been assessed over a three-year period (1984-1986) through a national interlaboratory quality-assurance program, conducted jointly by the Royal College of Pathologists of Australasia and the Australian Association of Clinical Biochemists. We investigated the precision and accuracy of individual methods and measurement systems routinely used in 14 urine assays. Assays of sodium, potassium, creatinine, glucose, and chloride were performed satisfactorily. Further improvement is required in assays of urinary osmolality, phosphate, and 5-hydroxyindoleacetic acid. Determinations of oxalate, urea, calcium, and 4-hydroxy-3-methoxymandelic acid are improving, but assays of protein and urate in urine present major problems for Australasian laboratories. In this program the sulfosalicylic acid turbidimetric method for urinary protein has consistently displayed poor precision plus a significant positive bias and should be abandoned. In contrast, the trichloroacetic acid-Ponceau S manual method has continued to perform well.

Evolution of a national urine quality assurance programme: the Australasian experience, 1981-1983.

A national interlaboratory quality assurance programme for quantitative urine analysis has been conducted over the past three years in Australasia under the auspices of the Royal College of Pathologists of Australasia and the Australian Association of Clinical Biochemists. Analysis of urine calcium has consistently improved over the three year period whereas urine protein analysis has consistently declined. Based on the findings in 1983, it is considered that urine sodium, potassium, creatinine, phosphate, glucose, and chloride are currently being measured satisfactorily by Australasian laboratories, while the analyses of urine proteins, urate, oxalate, 5-hydroxyindoleacetic acid and 4-hydroxy-3-methoxymandelic acid still require substantial improvement.

Mechanism of platelet interference with measurement of lactate dehydrogenase activity in plasma.

Platelets reportedly inhibit lactate dehydrogenase activity in plasma under reaction conditions of low osmolality. We describe observations inconsistent with these reports, and we attribute this "inhibition" to optical interference by platelets during the course of a reaction. We conclude that when platelet lysis is prevented and the optical interference of platelets corrected, platelet-rich plasma, platelet-poor plasma, and serum show essentially the same lactate dehydrogenase activity. Furthermore, platelet contamination can cause unexpected problems when lactate dehydrogenase is assayed with centrifugal analyzers. Results can be high or low, depending on the volume of diluent pipetted with the sample, and extreme within-run variations in activity are possible. When plasma is used instead of serum for routine analyses, regular checks for platelet contamination should be performed as a quality-control procedure, especially by laboratories separating plasma with bench-top centrifuges. Platelets can also interfere optically with assay of other enzymes and metabolites.

Six methods for determining urinary protein compared.

Inter-laboratory surveys have shown that "routine methods" of urinary protein determination are often unsatisfactory. Therefore, we compared six frequently used methods for determination of protein in urine with respect to linearity, within-batch and between-batch precision, comparative bias, and practicability. We assayed dilutions of human and bovine albumin and serum, and fresh and lyophilized human urine. We find that the AACC Selected Method has poor practicability and poor precision under routine conditions, but good linearity. The sulfosalicylic acid/biuret technique is also impracticable, requires a large sample, and is not linear at low concentrations of urine protein. The Coomassie Brilliant Blue technique has a narrow range of linearity and poor precision. The sulfosalicylic acid/sodium sulfate turbidimetric method is not precise and cannot be standardized with bovine materials. The Ponceau-S technique has good performance characteristics and practicability, and we recommend it for routine laboratory use.

A quality assurance programme for quantitative urine analyses.

Eighty-six Australasian laboratories participated in an interlaboratory quality assurance programme for 10 urine analytes. Twelve liquid samples were prepared from commercial lyophilized urine control material and distributed in 3 batches of 4. Use of pre-set acceptability limits for total laboratory error and target values facilitated timely feedback in graphic form. The samples had concentrations which were linearly related; this allowed simple calculation of overall imprecision and bias, graphic feedback of all submitted results, and comparison of performance between laboratories. A number of unsuitable and poor methods were identified. Particular attention must be paid, in future, to more widespread use of appropriate calibration and quality control materials, to avoidance of transcription and calculation errors, and to analysis of urine samples with elevated levels of analyte. Current laboratory performance can meet analytical goals for analyses of urine creatinine, phosphate, urate, and glucose but analysis of urine sodium, potassium, urea, calcium, osmolality, and proteins require a significant improvement.

An inter-laboratory survey of qualitative urinalysis.

An inter-laboratory survey of qualitative urinalysis was carried out in Australasia during 1981. Eighty-one laboratories analysed 6 samples of urine distributed in 3 batches of 2 at regular bimonthly intervals, mostly with commercially available reagent strips. Fewer than 30% of laboratories performed any form of quality control for analytes other than pH. Results indicated that improvement in the analysis of urine bilirubin, protein, glucose, ketones and blood is required, and recommendations to improve standards are made.

Investigation into paediatric bilirubin analyses in Australia and New Zealand.

A small regional survey of direct spectrophotometric methods and a larger Australian and New Zealand survey of paediatric bilirubin analyses are described. The overall performance of both groups was unsatisfactory with an unacceptable high interlaboratory variation. This interlaboratory variation was reduced significantly by the use of a spectrophotometric method with a common standard of methyl orange. The Australian and New Zealand survey also examined the "state of the art" for the measurement of conjugated bilirubin and showed that laboratories could not adequately measure conjugated bilirubin.

Short- and long-term biological variation in analytes in urine of apparently healthy individuals.

Intra-individual, interindividual, and analytical components of variation for each of 10 urine analytes were estimated from results obtained on analysis of urine specimens from 10 apparently healthy young men. In spot urines, urea and osmolality showed strong individuality, but intra-individual variances were larger than interindividual variances for sodium, urate, phosphate, and glucose. Urea and osmolality displayed strong individuality in daily urines, whereas sodium (when results were expressed in output terms), urate, potassium, and total protein (when results were expressed in concentration units) had intra-individual variances larger than interindividual variances. In monthly urines, calcium and glucose, in concentration terms, and phosphate, in output terms, exhibited strongest individuality. Analytical variance was a significant percentage of the total variance for total protein and glucose; the analytical methods we used for these analytes were probably unsatisfactory. A series of analytical goals for imprecision, based on biological variation, were derived. Although these goals may not be applicable in all clinical situations, they represent the beginning of a data base in the literature.

A clinical view of analytical goals in clinical biochemistry.

The analytical goals inferred desirable by a group of clinicians for the imprecisions of a wide range of analytes have been studied by survey. The goals required have not in general become more stringent in the past decade and are not as demanding as those promulgated by laboratory professionals. Clinical biochemistry laboratories can now attain analytical imprecisions which satisfy the general demands of clinicians except for analyses of calcium and of low levels of glucose. The lack of published data on analytical goals does not allow wide comparison of criteria for performance standards with the results of this study.

An inter-laboratory survey of paediatric bilirubin analyses.

A regional quality control trial of paediatric bilirubin analyses is described. The overall performance of the group was unsatisfactory with an unacceptably high inter-laboratory variation. The use of a common standard produced improvement in performance but it is concluded that the poor performance was also due to methodological problems. This lack of agreement between laboratories is a major problem when patients are transferred between hospitals.