Performance of the Cytoanalyzer in Recent Clinical Trials

The results of two clinical trials of the Cytoanalyzer are summarized. The first, conducted in 1958–59, included 1,184 smears, of which 21 were positive. Four hundred twenty-five (36.6%) of the negative smears received instrument scores lower than the lowest-scoring positive smear. In the second clinical trial, which took place in 1959–60, 58 of the 11,136 smears scanned by the Cytoanalyzer were positive. At the level of screening achieved in the first clinical trial (36.6%), a false-negative rate of 10.3 percent was incurred; that is, 6 of the 58 positive smears received scores within the selected negative range. This screening performance is considered inadequate for practical application of the instrument. An investigation of the mechanisms for screening revealed a direct relationship between the relative number of leukocytes in the smears and the instrument score achieved by the smears. This, in turn, was the result of nuclear aggregations, which increased in size and frequency with the proportion of leukocytes present and were responsible for most of the entries registered in the “abnormal” zone categories. Typical examples of normal and abnormal nuclei consistently failed to produce entries in the “normal” and “abnormal” zone categories, a result of the manner in which zone designations had been made. The inadequacies of smear-preparation techniques used in the clinical trials and the necessity of improving them are discussed.