COLLABORATIVE STUDY OF CONFIRMATORY TESTING PROCEDURES FOR SOMATIC CELLS IN MILK

Abstract

Collaborative studies were done to establish the experimental error (replicate variance) and the among-analyst variance of three modifications of the Direct Microscopic Somatic Cell Count and the Electronic Somatic Cell Count when used in laboratories that test milk routinely. The lowest total variance of logarithms of 0.00639 was obtained with the electronic procedure, followed by 0.00964 for the field counting modification of the Direct Microscopic Somatic Cell Count. The strip-reticle modification of the latter procedure had a total variance of 0.01251, and the Direct Microscopic Somatic Cell Count modification that involves counting all somatic cells on one strip without the use of a reticle had a variance of 0.03041. The coefficients of variation for the experimental error for the Electronic Somatic Cell Count and for the field counting, strip count with reticle, and strip count without reticle modifications of the Direct Microscopic Somatic Cell Count were 8, 17, 14, and 17%, respectively.