An evaluation of leucocyte analysis on the Coulter STKS

The performance of leucocyte analysis on the Coulter STKS (Coulter, Hialeah, FL, USA) was evaluated for accuracy, precision and reliability. The results were compared with those obtained from visual examination of a Romanowsky stained blood film together with the automated WBC-diff. from the Technicon H*1 (Technicon, Tarrytown, NY, USA). The relationship between the number of cells counted per WBC-diff. and the WBC count of the sample was established. Precision of the STKS WBC-diff. was acceptable on blood samples with normal and low WBC counts. Correlation with an 800 cell manual WBC-diff. (n = 104) was excellent (r = 0.97, 0.97, 0.83, 0.98 and 0.53 for neutrophils, lymphocytes, monocytes, eosinophils and basophils respectively). Blood specimens, collected into dipotassium EDTA, could be stored at 20-25 degrees C for at least 8 h with no significant effect on the STKS WBC-diff. In a study of 513 patient samples, the BLASTS suspect flag gave 5.4% false positives and zero false negatives, the VARIANT LYMPHS flag gave 1.5% false positives and 0.4% false negatives, and the IMM GRANS/BANDS flag gave 30.8% false positives and 2.3% false negatives. Several instrument and sample related problems were encountered during this study. Despite these limitations, the STKS can provide efficient 5 part WBC-diffs. and effective screening for WBC abnormalities.