Improved automated optical somatic cell counting method for raw milk: collaborative study

A collaborative study was conducted to compare the improved automated optical somatic cell counting procedure (OSCC II) with the direct microscopic somatic cell counting method (DMSCC) in raw milk. Samples were prefixed with formaldehyde and introduced into an Auto-Analyzer system. Dilution, clarification, and cell counting were performed automatically. Five collaborators participated in the study; they analyzed 48 samples in duplicate, using 2 different sampling rates. The results were compared with DMSCC counts reported by 3 different analysts. Statistical results show that the standard deviation for the DMSCC method is 0.0825 and for the OSCC II, at a sampling rate of 80/hr, 0.0434. When results are compared, the OSCC II procedure is as accurate as, and is significantly more precise than, the DMSCC method. The faster sampling rate of the OSCC II at 120/hr has some effect on precision but little effect on accuracy. The method has been adopted as official first action.