evaluation of the abbott cell-dyn 4000 hematology analyzer

Hematopathology / EVALUATION OF THE ABBOTT CELL-DYN 4000 HEMATOLOGY ANALYZER

Evaluation of the Abbott CELL-DYN 4000 HematologyAnalyzer

Ernesto Grimaldi, MD, and Francesco Scopacasa, PhD

Key Words: Abbott CD 4000; Blood cell counter; Automated hematology analyzer; Accuracy; Precision; Interference

A b s t r a c t

A new generation hematology analyzer, AbbottCELL-DYN 4000 (CD 4000), capable of providing 26parameters, including fully automated reticulocyte,nucleated RBC, blast, band, and immature granulocyte,and variant lymphocyte counts, was evaluated by usingthe National Committee for Clinical LaboratoryStandards H20-A protocol and compared with theBayer-Technicon H-2 analyzer, which is used routinelyin our laboratory. A lipid interference experiment and asample aging study also were performed. Linearity,carryover, and precision were within the limitsestablished by the manufacturer, and satisfactoryagreement was found with the H-2 analyzer. Theevaluation of leukocyte differential counts indicated anexcellent correlation with the manual reference methodfor neutrophils and lymphocytes, a good correlation formonocytes and eosinophils, and a poor correlation forbasophils in samples with low counts; for basophilcounts of 2% or higher, we found an improvement of thecorrelation coefficient. In the lipid interferenceexperiment, only hemoglobin determination wasinfluenced significantly on the CD 4000, but by using anew Abbott hemoglobin reagent, the interference waseliminated. The CBC and differential counts were stableand reportable up to at least 24 hours. Intrasampleviability information on leukocytes provided a qualitycheck on each individual specimen.

The Abbott CELL-DYN 4000 (CD 4000) (Abbott Diag-nostics, Abbott Park, IL) is a new generation fully automatedhematology analyzer that uses 4-angle argon laser light scatterand 2-color fluorescence flow cytometry.1 The analyzer providesthe laboratory with up to 26 blood count parameters, includingreticulocytes, immature reticulocyte fraction, nucleated RBCs,blasts, bands, immature granulocytes, and variant lymphocytes;in addition, fluorescence technology2 also provides a newintrasample 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 theH20-A protocol of the National Committee for Clinical Labora-tory Standards,4 the CBC and differential WBC count perfor-mance of the CD 4000 in comparison with a reference fullyautomated hematology analyzer in use in our laboratory, theBayer-Technicon H-2 (Bayer-Technicon, Tarrytown, NY) andwith the reference manual method (differential WBC countonly). We also evaluated the lipid interference on both instru-ments and the sample aging effects on CD 4000 measurements.

Materials and Methods

System Description

All analyses were performed on the Abbott CELL-DYN4000 using software version R4-12F without “individualized”laboratory settings for the laser scatter channels (Abbott setup).The system incorporates 4 different measurementtechnologies,1 including fluorescence flow cytometry, and usesan argon laser to undertake analyses of reticulocytes andnucleated RBCs in particular. The analyzer fluorometer section

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Grimaldi and Scopacasa / EVALUATION OF THE ABBOTT CELL-DYN 4000 HEMATOLOGY ANALYZER

has 2 fluorescence emission laser optics (4 angles of lightscatter). Blasts, immature granulocytes, bands, and variantlymphocytes are detected by a multiparameter, multiweighted,discriminant function; this function generates a flag andreports a confidence fraction from 0.50 to 0.99 (ie, the proba-bility that these cells were classified correctly). After detectionby the discriminant function, cell counts are estimated byusing light scatter. Determination of the hemoglobin concen-tration is based on spectrophotometry. The default systemmeasurements of the RBC and platelet counts are by imped-ance and optical methods, respectively; in addition, a simulta-neous determination of optical RBC and impedance plateletcounts are performed. Discrepancies between the 2 measure-ments provide an alert suggesting the presence of sampleinterferences.

Fluorescence technology also provides a new intrasamplequality control feature, the WBC viable fraction, determinedfrom the ratio of unstained to total WBCs. By combining theWBC viable fraction results with the fluorescence informa-tion, the CD 4000 can flag specimens (nonviable WBCs) forpotential sample deterioration.3

The CD 4000 and H-2 analyzers were calibratedfollowing the manufacturer’s guidelines and using their own“calibration samples”; the instruments were controlled byroutine quality control methods. The low, normal, and high“control samples” were supplied by the manufacturers.

Blood Samples

The evaluation of the instrument was performed byanalyzing blood specimens from routine samples afterobtaining patient’s informed consent.

Specimens were selected to span the full range of concen-trations expected in clinical practice, and at least half thesamples were from patients with blood disorders giving resultsin abnormal (low and high) ranges. In particular, for differen-tial WBC count abnormalities, 10% of these samples hadblasts, 20% immature granulocytes, 10% variant lymphocytes,5% nucleated RBCs, and 5% progranulocytes; 50% had noabnormalities; bands ranged from 0% to 20%. All sampleswere collected in evacuated 3.5-mL tubes containing EDTAK3 and were analyzed within 2 hours after obtaining the bloodsample. For the aging study, the samples were stored at roomtemperature or refrigerated (4 C) and analyzed within 24, 48,and 72 hours.

Carryover Assessment

Carryover assessment was performed according tomethod of Broughton5: a sample in the high range was tested 3consecutive times (H1, H2, H3), and a sample in the low rangewas tested 3 consecutive times (L1, L2, L3). The percentageof carryover for each parameter was calculated as follows:[(L1 – L3)/(H3 – L3)] ·100.

Linearity

Linearity was evaluated by analyzing serial dilutions of 5specimens in platelet-free autologous plasma.6 The resultswere evaluated in accordance with the International Councilfor Standardization in Haematology recommendation.5

Imprecision

For the between- and within-batch imprecision study, 20samples in triplicate and in 2 batches on the same day wereanalyzed. The instrument was switched off and recalibratedbetween the 2 batches.

The results were expressed as mean, SD, and coefficientof variation percentage.

Comparability

We selected 120 blood samples on the basis of the recom-mended International Council for Standardization in Haema-tology range of values7 and analyzed them side-by-side withthe CD 4000 and H-2 instruments. Calibration was donefollowing the manufacturer’s guidelines. Measured WBC,RBC, hemoglobin, mean corpuscular volume, platelet, anddifferential WBC count parameters were compared by linearregression analysis, and correlation coefficients (r) were calcu-lated. Since bands and immature granulocytes are countedtogether with neutrophils by the H-2 analyzer, these cells, welldefined by the CD 4000, were added to neutrophil counts inthe statistical evaluation.

We also compared 112 normal blood samples with themanual differential WBC count; all films were examined inde-pendently by 4 experienced technologists4; results werecompared by linear regression, and correlation coefficientswere calculated.

Interference Study

Lipid interference was evaluated in 10 blood samplesadded with increasing amounts of Intralipid (soya lipids)(Pharmacia AB, Uppsala, Sweden); they were analyzed side-by-side by using the 2 instruments, and each test wasperformed in triplicate. The results were expressed as themean value of 3 determinations. The lipid concentration wasmeasured as triglycerides.

At the end of the evaluation period, Abbott supplied anew hemoglobin reagent, Tri-Methyl-Tetra-Decyl-ammoniumchloride free (TTAB free), and a new software version (R8-1)that are able to eliminate any interference on CD 4000 hemo-globin determination. The lipid interference experiment alsowas 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 roomtemperature (25 C) or under refrigeration (4 C).

498 Am J Clin Pathol 2000;113:497-505 © American Society of Clinical Pathologists


Hematopathology / ORIGINAL ARTICLE

Results

Carryover

Carryover data for the WBC, RBC, hemoglobin, andplatelet values are given in ❚Table 1❚. The results for high tolow carryover testing were less than 0.5%.

Linearity

Linearity data are given in ❚Table 2❚. Excellent correla-tion was found between expected and obtained values forall parameters sensitive to dilution, also in a very lowrange. Statistical analysis revealed a correlation coefficienthigher than 0.997 for WBC, RBC, hemoglobin, and hemat-ocrit values and a lower correlation for platelet values(0.992). We also found that the unflagged percentage forthe WBC differential count results were reproducible andlinear down to a level of 0.20 ·109/L (data not shown).

Imprecision

As shown in ❚Table 3❚, there is good within- andbetween-batch reproducibility for all parameters, includingthe CBC and WBC differential counts. Only for basophilswas the coefficient of variation higher than 20%.

Comparability

As shown in ❚Table 4❚, the CD 4000 gave CBC anddifferential WBC count results that compared very wellwith data obtained by the H-2. The results for basophilsshowed poor agreement (r = 0.297) between the 2 instru-ments in the low range of counts and good agreement (r =0.920) for high basophils counts.

The results of correlation and linear regressionbetween the CD 4000 and manual differential are given in❚Table 5❚. Correlation was excellent for neutrophils andlymphocytes, and monocytes and eosinophils showed agood correlation, while basophils results yielded a lowercorrelation in the low range of values (<2%). The correla-tion for basophils became excellent when only sampleswith basophil values of 2% or higher (n = 25) wereconsidered.

The comparability data plot for the CD 4000 vs themanual differential count for the basophil counts, low andhigh ranges, are given in ❚Figure 1❚ and ❚Figure 2❚, respec-tively. The identity line is displayed together with the 95%

binomial confidence limits for a 400-cell differential WBCcount. In Figure 1, several outliers were identified by 95%confidence limits; no outliers were identified in Figure 2.

Interference Study

As shown in ❚Figure 3❚, a significant (P < .001) inac-curacy of the hemoglobin determinations was observed onboth instruments starting from a lipid value of 450 mg/dL,resulting a hemoglobin overestimation of 1 g/dL or more.Conversely, no interference was found with either instru-ment in the WBC and differential WBC counts (data notshown). The RBC and platelet counts in hyperlipidemicsamples ❚Figure 4❚ and ❚Figure 5❚ were overestimated onthe H-2 system, but only for high lipid concentrations,while no interference was found on the CD 4000. No moreinterference in the hemoglobin determination was observedusing the new Abbott hemoglobin reagent (TTAB free) andthe new software version ❚Figure 6❚.

Time (Aging) Study

In stored samples, no significant changes wereobserved in WBC, platelet, RBC and hemoglobin determi-nations by the CD 4000 (data not shown).

In the WBC count, the WBC viable fraction decreasedsignificantly (P < .001) between 24 and 48 hours, particu-larly in samples stored at room temperature ❚Figure 7❚. At48 hours, a significant (P < .001) increase of samplesshowing the nonviable WBC flag was observed ❚Figure 8❚.

No significant changes were observed in the differen-tial WBC count in stored samples; only a minor reductionin the proportion of eosinophils was noted in samplesstored for 48 hours at room temperature ❚Figure 9❚.Conversely, a significant (P < .001) change was observed inthe segmented neutrophil and band subpopulations ❚Figure

10❚. The time course shows a progressive decrease in thenumber of mature neutrophils (segmented) and a side-by-side, progressive increase in the number of bands; thisfeature is more evident in samples stored at 4 C ❚Figure

11❚. No significant changes were observed in immaturegranulocytes (Figure 10). In stored samples, the confidencefraction for neutrophil subpopulations was always less than0.76, whereas the fraction was always 0.76 or more in freshblood samples ❚Figure 12❚.

Discussion

In our study, the CELL-DYN 4000 reproducibility(between-batch and within-batch imprecision) results weresatisfactory with the exception of the basophil count.Furthermore, the CELL-DYN 4000 demonstrated minimalcarryover and a good linearity.


❚Table 1❚Percentage of Carryover in the CELL-DYN 4000 Analyzer*

WBC RBC Hemoglobin Platelets

0.05 0.38 0.32 0.50

* Abbott Diagnostics, Abbott Park, IL.




❚Table 2❚Linearity of the CELL-DYN 4000 Analyzer*

Range r Intercept Slope

WBC (·109/L) 0.15-100 0.998 0.030 0.998RBC (·1012/L) 0.17-7.0 0.997 –0.091 1.035Hemoglobin (g/dL) 0.50-20.0 0.999 –0.125 1.012Hematocrit (%) 1.5-60.0 0.999 –0.452 1.000Platelets (·109/L) 6.20-1,000 0.992 3.460 0.955


❚Table 3❚Within- and Between-Batch Precision Observed With the Abbott CELL-DYN 4000* in 20 Samples

Within Batch Between Batch

Mean SD CV (%) Mean SD CV (%)

WBC (·109/L) 8.02 0.19 2.44 8.10 0.20 2.47 RBC (·1012/L) 4.10 0.10 1.98 5.00 0.10 2.02 Hemoglobin (g/dL) 14.70 0.08 0.54 14.70 0.81 0.55 Hematocrit (%) 45.20 0.82 1.82 45.20 0.85 1.88 Mean corpuscular volume (fL) 90.50 0.28 0.31 90.30 0.27 0.30 Platelets (·109/L) 269.10 6.40 2.38 270.00 5.95 2.20 Neutrophils (%) 49.35 0.65 1.32 50.10 0.67 1.34 Lymphocytes (%) 40.79 0.63 1.55 41.00 0.63 1.53 Monocytes (%) 6.57 0.25 3.80 6.60 0.26 3.93 Eosinophils (%) 3.00 0.10 3.32 3.06 0.15 4.90 Basophils (%) 0.27 0.07 24.80 0.30 0.06 21.33


❚Table 4❚Comparability Test Between Abbott CELL-DYN 4000* and Bayer-Technicon H-2* for 120 Samples

Intercept Slope r

WBC (·109/L) 0.053 0.971 0.998RBC (·1012/L) –0.073 1.034 0.997Hemoglobin (g/dL) –0.035 1.018 0.998Mean corpuscular volume (fL) –6.606 1.019 0.990Platelets (·109/L) 2.147 0.911 0.986Neutrophils (%)† –0.061 0.970 0.981Lymphocytes (%)‡ 0.042 1.031 0.976Monocytes (%) 0.028 1.206 0.996Eosinophils (%) 0.285 1.053 0.975Basophils (%) Range of values, 0% to <2% 0.151 0.227 0.297Range of values, 2% to 10% 0.940 0.290 0.920

* Abbott Diagnostics, Abbott Park, IL, and Bayer-Technicon, Tarrytown, NY.† Segmented neutrophils, bands, and immature granulocytes.‡ Normal and variant lymphocytes.

❚Table 5❚Results of Inaccuracy Assessment: Comparison Between CELL-DYN 4000* and Manual Differential Leukocyte Count

Intercept Slope r

Neutrophils (%) 0.890 0.995 0.992Lymphocytes (%) 1.045 0.985 0.971Monocytes 0.630 0.888 0.830Eosinophils 0.400 0.925 0.888Basophils (%) Range of values, 0% to <2% 0.360 –0.009 –0.020Range of values, 2% to 10% 1.786 0.820 0.940




For the CBC and differential WBC counts, we found agood correlation with H-2 analyzer. Blasts and variantlymphocytes were both counted as large unstained cells bythe H-2, while they were well defined by the CD 4000;

therefore only neutrophil, lymphocyte, monocyte,eosinophil, and basophil data were comparable.

High nucleated RBCs would give invalid WBC compar-ison data (interference with the WBC count on the H-2


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❚Figure 1❚ Percentage of basophils with the CELL-DYN 4000(Abbott Diagnostics, Abbott Park, IL) compared with 400-cell manual differential count for basophil counts in the lowrange. The identity line is displayed with the 95% binomialconfidence limits. Few outliers are identified.

❚Figure 2❚ Percentage of basophils with the CELL-DYN 4000(Abbott Diagnostics, Abbott Park, IL) compared with 400-cell differential count for the basophil counts in the highrange. The identity line is displayed with the 95% binomialconfidence limits. No outliers are identified.

❚Figure 3❚ Interference of hyperlipidemic samples on thehemoglobin determination. Both the Abbott CELL-DYN 4000(Abbott Diagnostics, Abbott Park, IL) (squares) and Bayer-Technicon H-2 (Bayer-Technicon, Tarrytown, NY) (diamonds)show significant overestimation (1 g/dL or more) startingfrom a triglyceride value of 450 mg/dL or more.

❚Figure 4❚ Interference of hyperlipidemic samples on theRBC count. The RBC count is stable on both instruments(Abbott CELL-DYN 4000, Abbott Diagnostics, Abbott Park, IL[squares]; and Bayer-Technicon H-2 Bayer-Technicon, Tarry-town, NY [diamonds]) up to a triglyceride value of 200mg/dL. With higher lipid concentrations, only the H-2analyzer shows an RBC count overestimation.



analyzer). Because only a few samples with nucleated RBCspassed through the laboratory during this evaluation, a statisti-cally insignificant number of these samples was included in ourstudy (5%), and no interference with comparison was observed.

We also found a good correlation with the referencemanual differential for all WBC subpopulations except forbasophils in the low range (0% to <2%). Probably, the highcoefficients of variation for basophils and the poor correlation


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❚Figure 5❚ Interference of hyperlipidemic samples on theplatelet count. The platelet count performed by the AbbottCELL-DYN 4000 (Abbott Diagnostics, Abbott Park, IL)(squares) is stable up to a triglyceride value of 4,500 mg/dL.The platelet count by the Bayer-Technicon H-2 (Bayer-Tech-nicon, Tarrytown, NY) (diamonds) shows significant overes-timation starting from a triglyceride value of 1,200 mg/dL.

❚Figure 6❚ Interference of hyperlipidemic samples on thehemoglobin determination performed by CELL-DYN 4000(Abbott Diagnostics, Abbott Park, IL) using the new Abbotthemoglobin reagent (TriMethyl-Tetra-Decyl-Ammonium chlo-ride free) (squares) compared with the Bayer-Technicon H-2(Bayer-Technicon, Tarrytown, NY) (diamonds). No moreinterference on the hemoglobin determination wasobserved when using the new free hemoglobin reagent.

❚Figure 7❚ Time course of the WBC viable fraction in storedsamples. In the WBC count, the viable fraction decreasedsignificantly (P < .001) within 48 hours, particularly insamples stored at room temperature. Diamonds, samplesstored at 4 C; squares, samples stored at room temperature.

❚Figure 8❚ Nonviable WBC flag in stored samples. A significantincrease (P < .001) of samples showing the nonviable flag wasobserved only in samples stored more than 24 hours, espe-cially at room temperature. Gray bars, samples stored at roomtemperature; black bars, samples stored at 4 C.



between the 2 instruments are not related primarily to poorperformance of the analyzers for the WBC differentialcount but to the low number of basophils counted. The lowcorrelation with the reference method could be due to thelow number and irregular distribution of the cells in the

peripheral blood films or, more probably, to the interfer-ence of nonviable WBCs, which were present in all theidentified outliers. Finally, when analyzing samples withhigh basophil counts, a dramatic increase of the correlationcoefficient was found.


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❚Figure 9❚ Differential WBC count in stored samples. A, Only minor reduction in the proportion of eosinophils was observedin samples stored at room temperature. B, No significant changes were observed in samples stored at 4 C. Ne, neutrophils;Ly, lymphocytes; Mo, monocytes; Eo, eosinophils; Ba, basophils.

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❚Figure 10❚ Time course of neutrophil subpopulations insamples stored at room temperature. Significant changes(P < .001) were observed in the segmented neutrophil andband fractions: the time course shows a progressive reduc-tion in the proportion of segmented neutrophils and a side-by-side, progressive increase in the proportion of bands. Nochange in the immature granulocyte fraction was observed.Diamonds, segmented neutrophils; squares, bandneutrophils; triangles, immature granulocytes.

❚Figure 11❚ Time course of neutrophil subpopulations insamples stored at 4 C. In samples stored at 4 C, the timecourse shows a greater reduction in the fraction ofsegmented neutrophils and a greater progressive increasein the band fraction than in samples stored at room temper-ature. No change in the immature granulocyte fraction wasobserved. Diamonds, segmented neutrophils; squares,band neutrophils; triangles, immature granulocytes.



An excellent correlation for monocytes was found withthe H-2 analyzer (r = 0.990) and a moderate correlation withthe reference method (r = 0.830). This finding is in agree-ment with those of other reports8,9 and seems to be due toartifact distribution for these cells during preparation of theblood films and to difficulties in differentiating small mono-cytes from large lymphocytes.

In the lipid interference study, we observed, as expected,a significant (P < .001) inaccuracy of hemoglobin determina-tion on both instruments starting from a lipid value of 450mg/dL, while very high lipid amounts (4,800 mg/dL)showed no interference with the WBC, RBC, and plateletcounts performed by the CD 4000. These data suggest theadequacy of the Abbott CELL-DYN 4000 algorithm fordiscriminating high amounts of hyperlipidemic particles andexcluding them from counts as well. Finally, the AbbottTTAB free hemoglobin reagent improves the accuracy of thehemoglobin determination by the CD 4000 analyzer,including in samples with very high lipid amounts.

In stored samples, the increase in the percentage ofnonviable cells was much slower in refrigerated samples(4 C), while storage at higher temperatures induced an accel-eration of the process.

The apparent change in the relationship of segmentedneutrophils to bands (Figures 10 and 11) with storage time isopposite what might be expected with the passage of time.This apparent change should be due to the changes in

neutrophil nuclear morphologic features (loss of lobularity)in aged samples, as evident when examining the blood films.

Finally the WBC viable fraction, the nonviable WBCflag, and the confidence fraction are sensitive intrasamplequality checks, and they could contribute to increased accu-racy of the counts, particularly when the discriminationbetween mature granulocytes and bands is of clinicalinterest. In particular, the confidence fraction, which indi-cates the probability that a cell population was classifiedcorrectly, in our study was always 0.76 or more in samplesthat were not stored, whereas the confidence fraction wasalways less than 0.76 in stored samples for all WBC subsets.In fact, in the presence of high band counts, a WBC viablefraction of 95% or less and/or a nonviable WBC flag and/ora confidence fraction less than 0.76 could indicate sampledeterioration and, therefore, the need for a fresh sample.

Conclusions

Our evaluation data show that the Abbott CELL-DYN4000 is a precise device, and it is at least as accurate as theBayer-Technicon H-2. The results are linear to extremecounts, and no significant carryover was observed.

Derived from a DNA fluorescence analysis,2 the avail-ability of quantitative and qualitative viability informationfor WBCs is a new feature on a hematology analyzer and is avery useful tool for analyzing aged blood specimens. In addi-tion, we found that ease of use contributes to the CELL-DYN 4000 performance, which may prove very useful in theclinical laboratory. The Abbott CD 4000 analyzer representsa substantial advance in hematology instrumentation and hasconsiderable potential for extending the clinical role ofhematologic studies.

From the Department of Laboratory Medicine, UniversitàFederico II, Naples, Italy.

The CELL-DYN 4000 analyzer, reagents, and calibration andcontrol samples were provided free of charge for this evaluationby Abbott Diagnostics, Abbott Park, IL.

Address reprint requests to Dr Grimaldi: DipartimentoAssistenziale di Medicina di Laboratorio, PoliclinicoUniversitario Federico II, Via S Pansini 5, 80131 Napoli, Italy.

References

1. CELL-DYN 4000 [product manual]. Santa Clara, CA:Abbott Diagnostics; 1997.

2. Ormerod MG. Estimating cell viability, application in cellbiology. In: Ormerod MG, ed. Flow Cytometry: A PracticalApproach. New York, NY: IRL Press at Oxford UniversityPress; 1990:265-282.


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❚Figure 12❚ Time course of the confidence fraction in storedsamples. In samples stored at room temperature andsamples stored at 4 C, the confidence fraction (ie, the prob-ability that the cells were classified correctly) for segment-ed neutrophils, bands, and immature granulocytes wasalways less than 0.76, whereas the fraction was always0.76 or more in samples that were not stored.



3. D’Onofrio G, Zini G, Tommasi M, et al. Integration offluorescence and hemocytometry in the CELL-DYN 4000:reticulocyte, nucleated blood cell and white blood cellviability study. Lab Hematol. 1996;2:131-138.

4. National Committee for Clinical Laboratory Standards.Reference Leukocyte Differential Count (Proportional) andEvaluation of Instrumental Methods; Approved Standard.Villanova, PA: National Committee for Clinical LaboratoryStandards; 1992. NCCLS document H20-A. Vol 12.

5. Broughton PMG, Gowenlock AH, McCormach JJ, et al. Arecommended scheme for the evaluation of instruments forautomated analysis in the clinical biochemistry laboratory. JClin Pathol. 1969;22:278-285.

6. Shinton NK, England JM, Kennedy DA. Guidelines for theevaluation of instruments used in haematology laboratories.J Clin Pathol. 1982;35:1095-1100.

7. International Council for Standardization in HaematologyExpert Panel on Cytometry. Guidelines for the evaluation ofblood cell analyzer including those used for differentialleukocyte and reticulocyte counting and cell markerapplications. Clin Lab Haematol. 1994;16:157-174.

8. Lebeck LK, Amst BJ, Houwen B. Flow cytometric whiteblood cell differentials: a proposed alternate referencemethod. Sysmex J Int. 1993;3:61-65.

9. Goossens W, Van Hove L, Verwilghen RL. Monocytecounting: discrepancies in results obtained with differentautomated instruments. J Clin Pathol. 1991;3:44-49.



evaluation of the abbott cell-dyn 4000 hematology analyzer

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