L.A. Penberthy

A quality assurance programme for quantitative urine analyses

Summary Eighty‐six Australasian laboratories participated in an inter‐laboratory 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 significant improvement.

Analytical goals for quantitative urine analysis.

&NA; A regional survey of the performance of quantitative analysis of ten commonly requested urinary analytes was carried out in South Australia. Using the results achieved by the better laboratories as a basis, an empirical set of analytical goals for total laboratory error was derived; this is the first definition of such goals for quantitative urinary analysis. The goals are particularly for use in the assessment of laboratory performance in inter‐laboratory surveys.

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.

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

&NA; 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.

An inter-laboratory survey of qualitative urinalysis

Summary 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.

Improving neonatal bilirubin analyses

In an effort to improve the poor interlaboratory performance of neonatal bilirubin analyses we have investigated various methodologies and forms of standardization. We found that a spectrophotometric method has significant advantages in terms of technical simplicity and gives improved precision. However the accuracy of this method depends on careful selection of the wavelengths used and on validated absorbance factors used to calculate results. We suggest that methyl orange is used as an artificial standard in conjunction with the spectrophotometric method for total bilirubin and that this standard is calibrated by a reference laboratory and subsequently distributed to laboratories in the same geographical area for use as a common standard.

The inadequacy of neonatal bilirubin analyses. A report from the South Australian A.A.C.B. quality control committee

Following concern shown by members of the South Australian A.A.C.B. Quality Control Committee regarding neonatal bilirubin analyses, a survey was conducted to investigate the performance of laboratories in this State. Preliminary investigations showed that varying methods of assay, standardization and quality control were being used by participating laboratories. We found that: (i) Within-laboratory precision was unsatisfactory; (ii) Inter-laboratory accuracy was unsatisfactory; (iii) Not one method stood out as clearly being the method of choice; (iv) Lyophilized ‘standard’ material may contribute to the poor inter-laboratory precision. This short communication will summarize the information from this survey and also suggest methods for improvement of inter-laboratory accuracy and precision for neonatal bilirubin analyses.