Notes for Contributors

had been unused for some time within the calibration period could give erroneously low results. This was most likely to happen if a series of urine samples were analysed followed by a serum, but the .effect was by no means reproducible. The manufacturer is aware of this problem, which is probably caused by deterioration of the reagent in the measuring cup, and is taking steps to correct it. Creatinine The Astra system seems to have overcome many of the problems associated with the kinetic Jaffe procedure. The method is precise and free from interference by bilirubin and haemoglobin except at very high concentrations. The interference by methyl dopa has been previously described [3]. With these reservations, the Astra was found to be a precise and accurate instrument for the measurement of electrolytes, urea, glucose and creatinine in serum and urine. It is easy to use, requiring only simple routine maintenance on a daily, weekly, and monthly routine. In the event of a failure of almost any part of the system, the RAPid kit enables the user to replace defective modules easily and quickly. It could comfortably analyse 200-300 specimens per day and is therefore particularly suitable for the medium-sized laboratory. It would also be suitable for use in larger laboratories to handle emergency specimens by day or night and to back up a larger multichannel analyser. It is similar in speed and capability to other instruments but has the advantage of analysing serum urea, creatinine, glucose, and electrolytes together and it will also analyse urine specimens. ACKNOWLEDGEMENTS The authors are indebted to Beckman RIIC Ltd for making the Astra-8 available for this evaluation. The assistance of Mr G Greaves and Mr R Bunce, who inspected the electrical and mechanical aspects of the machine is acknowledged, and also that of Mrs M Peters, Mr R Holder and Mr J Parekh for their help with the analysis of the results.