Measurement and standard reference materials in clinical chemistry.

The concepts of the measurement system based upon four parameters-length (meter), mass (kilogram), time (second), and temperature (kelvin) -are developed. The proper daily operation of an analytic laboratory depends upon these basic measurements and others derived from them, eg., the liter. An additional component of chemical measurement which directly influences accuracy is the purity of the standards ici reagents employed. The standard reference materials program of the National Bureau of Standards provides a central source of guaranteed high-purity reference materials which are available to all. The reliability of chemical measurements should increase as new standard reference materials such as cholesterol, uric acid, urea, and creatinine are utilized to standardize methoJs and to calibrate instruments in the clinical laboratories of this country.