Laboratory standardizatin in an international study: the Kaunas--Rotterdam intervention study (KRIS).

Laboratory results obtained in different laboratories over lengthy periods of time usually are difficult to compare. In cooperative long-term studies where such results must be pooled, thorough standardization of methods is vital. We describe a program in which comparable plasma cholesterol and glucose analyses have been obtained, by simple methods. In the Netherlands and the Soviet Union in close collaboration with the Center for Disease Control, Atlanta, Ga., U.S.A. The two laboratories produced glucose values (direct o-toluidine reaction) within 2% of the target reference values and cholesterol results (direct Liebermann-Burchard reaction) with a consistent 6-8% positive bias over the reference method values. Intralaboratory precision was subject to preset acceptance limits. The use of common control materials, exchange of patient samples, and on-site comparison of all details of laboratory procedures are vital tools in standardization efforts. A laboratory protocol that included quality requirements and rejection criteria was developed and proved to be indispensable. The experience gained should be useful in standardizing inter-laboratory results in similar studies.