Hematopathology / EVALUATION OF THE ABBOTT CELL-DYN 4000 HEMATOLOGY ANALYZER
Evaluation of the Abbott CELL-DYN 4000 Hematology Analyzer Ernesto Grimaldi, MD, and Francesco Scopacasa, PhD Key Words: Abbott CD 4000; Blood cell counter; Automated hematology analyzer; Accuracy; Precision; Interference
A new generation hematology analyzer, Abbott CELL-DYN 4000 (CD 4000), capable of providing 26 parameters, including fully automated reticulocyte, nucleated RBC, blast, band, and immature granulocyte, and variant lymphocyte counts, was evaluated by using the National Committee for Clinical Laboratory Standards H20-A protocol and compared with the Bayer-Technicon H-2 analyzer, which is used routinely in our laboratory. A lipid interference experiment and a sample aging study also were performed. Linearity, carryover, and precision were within the limits established by the manufacturer, and satisfactory agreement was found with the H-2 analyzer. The evaluation of leukocyte differential counts indicated an excellent correlation with the manual reference method for neutrophils and lymphocytes, a good correlation for monocytes and eosinophils, and a poor correlation for basophils in samples with low counts; for basophil counts of 2% or higher, we found an improvement of the correlation coefficient. In the lipid interference experiment, only hemoglobin determination was influenced significantly on the CD 4000, but by using a new Abbott hemoglobin reagent, the interference was eliminated. The CBC and differential counts were stable and reportable up to at least 24 hours. Intrasample viability information on leukocytes provided a quality check on each individual specimen.
© American Society of Clinical Pathologists
The Abbott CELL-DYN 4000 (CD 4000) (Abbott Diagnostics, Abbott Park, IL) is a new generation fully automated hematology analyzer that uses 4-angle argon laser light scatter and 2-color fluorescence flow cytometry.1 The analyzer provides the laboratory with up to 26 blood count parameters, including reticulocytes, immature reticulocyte fraction, nucleated RBCs, blasts, bands, immature granulocytes, and variant lymphocytes; in addition, fluorescence technology2 also provides a new intrasample quality control feature, the WBC viable fraction.3 A “confidence fraction” for blasts, bands, immature granulocytes, and variant lymphocytes also was provided.1 During a 3-month period, we evaluated, on the basis of the H20-A protocol of the National Committee for Clinical Laboratory Standards,4 the CBC and differential WBC count performance of the CD 4000 in comparison with a reference fully automated hematology analyzer in use in our laboratory, the Bayer-Technicon H-2 (Bayer-Technicon, Tarrytown, NY) and with the reference manual method (differential WBC count only). We also evaluated the lipid interference on both instruments and the sample aging effects on CD 4000 measurements.
Materials and Methods System Description All analyses were performed on the Abbott CELL-DYN 4000 using software version R4-12F without “individualized” laboratory settings for the laser scatter channels (Abbott setup). The system incorporates 4 different measurement technologies,1 including fluorescence flow cytometry, and uses an argon laser to undertake analyses of reticulocytes and nucleated RBCs in particular. The analyzer fluorometer section Am J Clin Pathol 2000;113:497-505
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Abstract
Grimaldi and Scopacasa / EVALUATION OF THE ABBOTT CELL-DYN 4000 HEMATOLOGY ANALYZER
Blood Samples The evaluation of the instrument was performed by analyzing blood specimens from routine samples after obtaining patient’s informed consent. Specimens were selected to span the full range of concentrations expected in clinical practice, and at least half the samples were from patients with blood disorders giving results in abnormal (low and high) ranges. In particular, for differential WBC count abnormalities, 10% of these samples had blasts, 20% immature granulocytes, 10% variant lymphocytes, 5% nucleated RBCs, and 5% progranulocytes; 50% had no abnormalities; bands ranged from 0% to 20%. All samples were collected in evacuated 3.5-mL tubes containing EDTA K3 and were analyzed within 2 hours after obtaining the blood sample. For the aging study, the samples were stored at room temperature or refrigerated (4 C) and analyzed within 24, 48, and 72 hours. Carryover Assessment Carryover assessment was performed according to method of Broughton5: a sample in the high range was tested 3 consecutive times (H1, H2, H3), and a sample in the low range was tested 3 consecutive times (L1, L2, L3). The percentage of carryover for each parameter was calculated as follows: [(L1 – L3)/(H3 – L3)] ·100. 498
Am J Clin Pathol 2000;113:497-505
Linearity Linearity was evaluated by analyzing serial dilutions of 5 specimens in platelet-free autologous plasma.6 The results were evaluated in accordance with the International Council for Standardization in Haematology recommendation.5 Imprecision For the between- and within-batch imprecision study, 20 samples in triplicate and in 2 batches on the same day were analyzed. The instrument was switched off and recalibrated between the 2 batches. The results were expressed as mean, SD, and coefficient of variation percentage. Comparability We selected 120 blood samples on the basis of the recommended International Council for Standardization in Haematology range of values7 and analyzed them side-by-side with the CD 4000 and H-2 instruments. Calibration was done following the manufacturer’s guidelines. Measured WBC, RBC, hemoglobin, mean corpuscular volume, platelet, and differential WBC count parameters were compared by linear regression analysis, and correlation coefficients (r) were calculated. Since bands and immature granulocytes are counted together with neutrophils by the H-2 analyzer, these cells, well defined by the CD 4000, were added to neutrophil counts in the statistical evaluation. We also compared 112 normal blood samples with the manual differential WBC count; all films were examined independently by 4 experienced technologists4; results were compared by linear regression, and correlation coefficients were calculated. Interference Study Lipid interference was evaluated in 10 blood samples added with increasing amounts of Intralipid (soya lipids) (Pharmacia AB, Uppsala, Sweden); they were analyzed sideby-side by using the 2 instruments, and each test was performed in triplicate. The results were expressed as the mean value of 3 determinations. The lipid concentration was measured as triglycerides. At the end of the evaluation period, Abbott supplied a new hemoglobin reagent, Tri-Methyl-Tetra-Decyl-ammonium chloride free (TTAB free), and a new software version (R8-1) that are able to eliminate any interference on CD 4000 hemoglobin determination. The lipid interference experiment also was performed with these new components. Time (Aging) Study We analyzed 25 normal samples in duplicate within 2, 24, 48, and 72 hours after venipuncture and storage at room temperature (25 C) or under refrigeration (4 C). © American Society of Clinical Pathologists
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has 2 fluorescence emission laser optics (4 angles of light scatter). Blasts, immature granulocytes, bands, and variant lymphocytes are detected by a multiparameter, multiweighted, discriminant function; this function generates a flag and reports a confidence fraction from 0.50 to 0.99 (ie, the probability that these cells were classified correctly). After detection by the discriminant function, cell counts are estimated by using light scatter. Determination of the hemoglobin concentration is based on spectrophotometry. The default system measurements of the RBC and platelet counts are by impedance and optical methods, respectively; in addition, a simultaneous determination of optical RBC and impedance platelet counts are performed. Discrepancies between the 2 measurements provide an alert suggesting the presence of sample interferences. Fluorescence technology also provides a new intrasample quality control feature, the WBC viable fraction, determined from the ratio of unstained to total WBCs. By combining the WBC viable fraction results with the fluorescence information, the CD 4000 can flag specimens (nonviable WBCs) for potential sample deterioration.3 The CD 4000 and H-2 analyzers were calibrated following the manufacturer’s guidelines and using their own “calibration samples”; the instruments were controlled by routine quality control methods. The low, normal, and high “control samples” were supplied by the manufacturers.
Hematopathology / ORIGINAL ARTICLE
binomial confidence limits for a 400-cell differential WBC count. In Figure 1, several outliers were identified by 95% confidence limits; no outliers were identified in Figure 2.
Results Carryover Carryover data for the WBC, RBC, hemoglobin, and platelet values are given in ❚Table 1❚. The results for high to low carryover testing were less than 0.5%.
Imprecision As shown in ❚Table 3❚ , there is good within- and between-batch reproducibility for all parameters, including the CBC and WBC differential counts. Only for basophils was the coefficient of variation higher than 20%. Comparability As shown in ❚Table 4❚, the CD 4000 gave CBC and differential WBC count results that compared very well with data obtained by the H-2. The results for basophils showed poor agreement (r = 0.297) between the 2 instruments in the low range of counts and good agreement (r = 0.920) for high basophils counts. The results of correlation and linear regression between the CD 4000 and manual differential are given in ❚Table 5❚. Correlation was excellent for neutrophils and lymphocytes, and monocytes and eosinophils showed a good correlation, while basophils results yielded a lower correlation in the low range of values (
