Why Plasma Electrolytes?

The real value of the budget available for clinical chemistry in this country is unlikely to increase for some years. Any expansion and development must therefore be balanced by economies: either we do less or we do what we do more cheaply. Plasma electrolytes are generally regarded as simple, precise, useful, cheap measurements which it is worthwhile to make as part of a screening procedure. These measurements led the way in the explosive increase in the workload of clinical chemistry; they are the major determinant of the workload of most laboratories, and of the size and, therefore, of the cost of the large capacity multi­ channel analysers required by large laboratories. A reduction in the 'plasma electrolyte' workload would achieve large savings. The subject of plasma electrolytes is clearly a large and important one, and I will discuss briefly only three aspects: usefulness, need, and cost. By plasma electrolytes I mean the plasma concen­ trations of sodium, potassium, urea, chloride, bicarbonate, and creatinine. The first three are undoubtedly regarded as the core measurements, but in many laboratories all are done as part of a set of analyses on one analyser. Sodium