Leukocyte analysis and differentiation using high speed microfluidic single cell impedance cytometry

Miniature high speed label-free cell analysis systems have yet to be developed, but have the potential to deliver fast, inexpensive and simple full blood cell analysis systems that could be used routinely in clinical practice. We demonstrate a microfluidic single cell impedance cytometer that performs a white blood cell differential count. The device consists of a microfluidic chip with micro-electrodes that measure the impedance of single cells at two frequencies. Human blood, treated with saponin/formic acid to lyse erythrocytes, flows through the device and a complete blood count is performed in a few minutes. Verification of cell dielectric parameters was performed by simultaneously measuring fluorescence from CD antibody-conjugated cells. This enabled direct correlation of impedance signals from individual cells with phenotype. Tests with patient samples showed 95% correlation against commercial (optical/Coulter) blood analysis equipment, demonstrating the potential clinical utility of the impedance microcytometer for a point-of-care blood analysis system.

Multistation multiparameter flow cytometry: a critical review and rationale

The capacity for fluorescence excitation by beams of different wavelengths at separate points along the sample stream, and the capacity for computer analysis of multiparameter data thus obtained, are now available in flow cytometer/sorter systems from commercial producers. It is now readily apparent to most experienced users of flow cytometers that such multiparameter analysis offers the most convenient solution to the problem of characterizing subpopulations of cells within a mixed population. The use of multiple beams facilitates resolution of fluorescence signals from several probes within or upon a single cell and widens the range of analytical alternatives available to experimenters. This critical review discusses the history of the instrumentation, the parameters now measurable and the probes used for their measurement, and the methods for data analysis. Required sensitivity and precision are discussed, leading to the conclusion that many of the advantages of multistation, multiparameter flow cytometry can be made available in less complex and less costly instruments using less powerful sources and less elaborate computer hardware than are presently incorporated in commercial apparatus.

The new hematology analyzer Sysmex XE-2100: performance evaluation of a novel white blood cell differential technology

CONTEXT

The new hematology analyzer Sysmex XE-2100 (TOA Medical Electronics, Kobe, Japan) has a novel, combined, white blood cell differential technology and a special reagent system to enumerate nucleated red blood cells.

DESIGN

Performance evaluation of both technologies of the Sysmex XE-2100 according to the H20-A protocol of the National Committee for Clinical and Laboratory Standards and comparison of the results with those for the hematology analyzer Sysmex NE-8000 (TOA Medical Electronics).

SPECIMENS

Five hundred forty-four blood samples randomly chosen from various inpatient and outpatient departments of the Vienna University hospital.

RESULTS

Five-part white blood cell differential counts on the XE-2100 revealed excellent correlation with the manual reference method for neutrophils, lymphocytes, and eosinophils (r =.925,.922, and.877, respectively) and good correlation for monocytes and basophils (r =.756 and.763, respectively). The efficiency rates of flagging for the presence of >/=1% abnormal white blood cells were 83% (XE-2100) and 66% (NE-8000). The correlation of automated and microscopic nucleated red blood cell counts was excellent (r =.97).

CONCLUSIONS

From the present evaluation and our former experience with other types of Sysmex analyzers, we conclude that the new white blood cell differential technology of the XE-2100 represents a further development toward more efficient flagging of abnormal white blood cells.

New quantitative parameters on a recently introduced automated blood cell counter--the XE 2100

The XE 2100 (Sysmex Corporation) is a cell counter that furthers the technology of fluorescent flow cytometry developed from the earlier range of Sysmex analysers. The new diagnostic features are a nucleated red cell count (NRBC), the ability to measure platelets by impedance as well as an 'optical' platelet count using a fluorescence dye and an immature granulocyte (IG) count. The NRBC count was highly correlated (r = 0.97) with the manual reference count. For counts below 100 x 109/l the 'optical' method and the immunocount gave good a correlation (r = 0.97) optical and impedance counts were also well correlated (r = 0.89). The use of the 'optical' platelet count significantly improves the reliability of low platelet counts. The IG count correlated with visual counts (r = 0.81) and allows the detection of immature cells at an earlier stage in the laboratory process. The introduction of fluorescent flow cytometric analysis allows extended quantification of additional cell populations and so potentially improves screening and monitoring of various pathological conditions.

Examination of peripheral blood films using automated microscopy; evaluation of Diffmaster Octavia and Cellavision DM96

BACKGROUND

Differential counting of peripheral blood cells is an important diagnostic tool. Yet, this technique requires highly trained staff, is labour intensive and has limited statistical reliability. A recent development in this field was the introduction of automated peripheral blood differential counting systems. These computerised systems provide an automated morphological analysis of peripheral blood films, including a preclassification of both red and white cells (RBCs and WBCs, respectively).

AIMS

To investigate the ability of two automated microscopy systems to examine peripheral blood smears.

METHODS

Two automated microscopy systems, the Cellavision Diffmaster Octavia (Octavia) and Cellavision DM96 (DM96), were evaluated.

RESULTS

The overall preclassification accuracy values for the Octavia and the DM96 systems were 87% and 92%, respectively. Evaluation of accuracy (WBC analysis) showed good correlation for both automated systems when compared with manual differentiation. Total analysis time (including post classification) was 5.4 min/slide for the Octavia and 3.2 min/slide for the DM96 (100 WBC/slide) system. The DM96 required even less time than manual differentiation by an experienced biomedical scientist.

CONCLUSIONS

The Octavia and the DM96 are automated cell analysis systems capable of morphological classification of RBCs and WBCs in peripheral blood smears. Classification accuracy depends on the type of pathological changes in the blood sample. Both systems operate most effectively in the analysis of non-pathological blood samples.

Spurious counts and spurious results on haematology analysers: a review. Part II: white blood cells, red blood cells, haemoglobin, red cell indices and reticulocytes

Haematology analysers provide quick and accurate results in most situations. However, spurious results, related either to platelets (part I of this report) or to other parameters from the cell blood count (CBC) may be observed in several instances. Spuriously low white blood cell (WBC) counts may be observed because of agglutination in the presence of ethylenediamine tetra-acetic acid (EDTA). Cryoglobulins, lipids, insufficiently lysed red blood cells (RBC), erythroblasts and platelet aggregates are common situations increasing WBC counts. In most of these instances flagging and/or an abnormal WBC differential scattergram will alert the operator. Several situations lead to abnormal haemoglobin measurement or to abnormal RBC count, including lipids, agglutinins, cryoglobulins and elevated WBC counts. Mean (red) cell volume (MCV) may be also subject to spurious determination, because of agglutinins, excess of glucose or salts and technological considerations. In turn, abnormality related to one measured parameter will lead to abnormal calculated RBC indices: mean cell haemoglobin content (MCHC) is certainly the most important RBC indices to consider, as it is as important as flags generated by the haematology analysers (HA) in alerting the user to a spurious result. In many circumstances, several of the measured parameters from CBC may be altered, and the discovery of a spurious change on one parameter frequently means that the validity of other parameters should be considered. Sensitive flags now allow the identification of several spurious counts, but only the most sophisticated HA have optimal flagging and more simple HA, especially those without a WBC differential scattergram, do not possess the same sensitivity for detecting anomalous results. Reticulocytes are integrated now into the CBC in many HA, and several situations may lead to abnormal counts.

Peripheral blood film review. The demise of the eyecount leukocyte differential

The automated hematology analyzer with CBC and differential results has replaced the traditional manual or individual assay methods for hematologic parameters and the eyecount leukocyte differential as the initial screening and detection system for hematologic abnormalities in modern hospitals and clinics. The traditional review of all automated hematology instrument results by preparation, staining, and microscopic examination of a blood film has disappeared in most institutions. The reasons are the more accurate detection of specimens with distributional or morphologic abnormalities by the instruments than by the traditional eyecount method. The opportunity for a clinician to request a microscopic examination of a blood film, whether or not it is flagged, must be preserved, because the clinician's knowledge of the patient's history, physical findings, and current or prior therapy may indicate review to discover an abnormality that may not have been apparent from the instrument results alone. There has also been a dramatic reduction of the numbers of medical technologists and technicians in medical laboratories. Automation of the CBC and differential counts has reduced the number of technologists needed for performance of these tests. But other factors have had a negative effect, such as the necessity to reduce costs. Consolidation of hematology and chemistry laboratories in core laboratories may produce savings in labor costs, but may also create problems of creating and maintaining areas of expertise, such as hematologic morphology, because of the cross-training required and the necessity of personnel to do all things. This article suggests and documents a number of measures that can be infinity stituted by the laboratory and by clinicians to reduce the number of eyecount differentials and blood film reviews that need to be performed. The first effort is to convince clinicians that valid data exist that confirm that a policy of allowing the laboratory to initiate blood film review based on findings of the CBC and automated differential is a more sensitive and accurate method of detecting patients with blood film abnormalities than routine blood film review of all specimens by technologists. Clinicians need to recognize that daily differential results or differentials at intervals of less than a week are not medically necessary in most patients. The laboratory, however, must provide opportunities for the clinician to request differentials at any time for specific medical reasons. The laboratory must establish the validity of screening criteria for detection of distribution and morphologic abnormalities of leukocytes by clinical correlation studies or adopt criteria established by laboratories with the same instrumentation and which have conducted clinical evaluations. A final observation on the eyecount differential is that it was the only way to identify cell types and their relative proportion for nearly 100 years. Cells were identified by their shape, intracellular structures, and staining characteristics. Many studies were able eventually to correlate some aspect of each cell type's function with their morphologic appearance. It has also been learned that the bone marrow is the source of production of most circulating cells and a great deal of the controls of cell production and release into the peripheral blood have been learned. But leukocytes have many functions, almost none of which are performed in the peripheral blood. The peripheral blood is mainly a conduit from the bone marrow to the tissues where the leukocytes perform their function in the case of the neutrophils and monocytes. It is mainly a recirculation and redistribution system for lymphocytes that usually receive their instructions from antigen processing cells in the tissues and allow these modified cells to home to sites where their functions occur. Cellular morphology and staining characteristics tell little about the maturation stage and functional capabilities of leukocytes. One cannot tell the difference between a band and a segmented neutrophil or whether a lymphocyte is a T or B cell on the conventional eyecount differential. One cannot tell the mature granulocyte of a patient with chronic myeloid leukemia from a normal mature neutrophil. Increasingly, techniques are being developed to identify better the maturation stages of cells and association with specific functional capabilities by flow cytometric techniques. The neoplastic nature of some normal-appearing leukocytes can be identified by techniques, such as fluorescent in situ hybridization. With the rapid advances in many approachs to understand the nature and functional capability of leukocytes, the eyecount differential with the traditional Romanowsky stain may be past the apogee of its ascent and beginning its trip into history along with the hemocytometer counting chamber and the Sahli pipet. The development and implementation of new laboratory cornerstone techniques for diagnosis of hematologic disease are eagerly awaited. On the other hand, the red cells and platelets exist to function in the peripheral blood. More emphasis is needed in the development of automated methods of determining the nature and functional capabilities of these true blood cells as part of the CBC.

Large-volume hemocytometer chamber for accurate counting of white cells (WBCs) in WBC-reduced platelets: validation and application for quality control of WBC-reduced platelets prepared by apheresis and filtration

A detailed description is provided of a method using a large-volume (50 microL) hemocytometer to count very low numbers of white cells (WBCs) in platelet components. A method employing a Nageotte hemocytometer uses crystal violet stain and a standard microscope with a reading time of 5 to 10 minutes. The method is validated by using serial dilutions of known concentrations of WBCs in platelets and by correlation with a flow cytometric technique. The interobserver coefficient of variation was 11.9 percent for WBC concentrations > 2 per microL. Use of the method for the evaluation of 203 WBC-reduced platelet components prepared by apheresis or by filtration revealed that over 94 percent of components had WBC content < 5 x 10(6). This method could easily be applied in the routine quality control of WBC-reduced platelet components and in clinical studies employing these components.

Validation of a simple method to count very low white cell concentrations in filtered red cells or platelets

The increased performance of white cell (WBC) filters makes it difficult to count precisely the number of residual WBCs. Concentrations as low as 0.01 WBC per microL cannot be determined with electronic cell counters, conventional hemocytometers, or the flow cytometric techniques currently being used. This article describes a simple, manual method using a Nageotte hemocytometer with a large-volume chamber (50 microL) to count the number of WBCs contained in red cell (RBC) suspensions (preparations A, B, and C) and in platelet suspensions (preparation D) diluted 1 in 10 pure, or concentrated two fold. To validate the method, several reference ranges, prepared by successively adding mononuclear cells to a suspension of pure RBCs or platelets, were used. Among the different series, validation ranges varied from 0.2 to 12 to 0.01 to 0.5 WBCs per microL and correlation coefficients ranged from 0.929 to 0.996. To determine the limit of accurate detection, accuracy tests (n = 160) were carried out by two experienced operators on samples with WBC concentrations of about 5, 10, and 120 times the concentration at the theoretical limit of detection (1 WBC/chamber). No significant difference was observed in the various types of preparations (A, B, C, D) in the tests performed by the two operators. However, intra-assay coefficients of variation were 18, 9.5, and 2.2 percent, respectively, at WBC concentrations of 5, 10, and 120 times that at the theoretical limit of detection. These observations show that a limit of accurate detection (10%) seems to be reached when 10 cells are observed in a Nageotte hemocytometer.(ABSTRACT TRUNCATED AT 250 WORDS)

Validation of automated blood cell counter for the determination of polymorphonuclear cell count in the ascitic fluid of cirrhotic patients with or without spontaneous bacterial peritonitis

OBJECTIVES

Polymorphonuclear (PMN) cell count in ascitic fluid is the most useful test for the diagnosis of spontaneous bacterial peritonitis (SBP). We evaluated the validity of an automated blood cell counter for the PMN determination in ascitic fluid by comparing it with the traditional hematologic method with a light microscope in a manual counting chamber.

METHODS

A total of 130 ascitic fluid samples were collected from 74 consecutive cirrhotics. The agreement between the two techniques was assessed according to Bland and Altman's method. The sensitivity, specificity, and positive and negative predictive values of the automated blood cell counter were calculated by considering the diagnosis of SBP as a PMN count > or = 250 cells/mm(3), determined by the manual method as the "gold standard."

RESULTS

The mean PMN counts assessed by the manual method and the automated blood cell counter were 124 +/- 301 cells/mm(3) and 130 +/- 339 cells/mm(3), respectively (p = 0.89, ns). The mean +/- SD of the difference between manual and automated measurements was 6 +/- 61 cells/mm(3), whereas the limits of agreement were +127 cells/mm(3) (95% CI = +108 to +147) and -115 cells/mm(3) (95%CI = -96 to -135). SBP was diagnosed in 11 patients. All but one were correctly identified with the automated blood cell counter, with a sensitivity of 94% and a specificity of 100%; positive and negative predictive values were 100% and 99.1%, respectively.

CONCLUSIONS

The manual method and the automated blood cell counter have a good agreement in the PMN determination in ascitic fluid, and the automated blood cell counter is a reliable tool for rapid diagnosis of SBP.

Point-of-care method for total white cell count: an evaluation of the HemoCue WBC device

Point-of-care testing (POCT) is becoming an important adjunct to haematology laboratory practice. An important component of the blood count is the total white cell count (WBC). Previously, this required laborious microscopic cell counting, but it can now be performed by means of automation; however, in many under-resourced countries, costly automated counters are only available in very few central hospitals. Moreover, neither method is practical in most POCT situations. The HemoCue WBC has been developed as a simplified alternative method, consisting of a reagent pre-loaded disposable cuvette together with basic image analysis technology. This report describes an assessment of its utility. The WBC of 500 routine blood samples from the hospital were tested in parallel by the HemoCue WBC and by a reference analyser to assess accuracy and utility of the former. The tests included precision, linearity, type of blood sample and anticoagulant and potential interfering substances in blood specimens. In the tests for accuracy, 192 of the 200 showed percentage difference from the NEQAS reference of <10% whilst the remaining eight samples differed by <12%, thus meeting the requirements of Clinical laboratory improvement amendments (CLIA)-88 regulations. Of the samples tested with potential interfering substances only those with >2% normoblasts or reticulocytosis showed significant differences from the reference measurements. The HemoCue WBC is reliable for WBC counts within the analytical range of 0.4-30.0 x 10(9)/l, except in samples where there are significant numbers of normoblasts or reticulocytes. It is simple to use and provides a valuable advance in the facilities available for POCT in haematology.

Leukoreduction of blood components

During the past year, blood component therapy witnessed two quite contradictory trends in the area of leukoreduction. On the one hand, the year saw widespread forced implementation of leukoreduction by several national blood suppliers, including the American Red Cross, who refused to sell hospitals nonleukoreduced blood. The forced implementation came at high cost to hospitals and with the strong endorsement of the US Food and Drug Administration, which stopped short of mandating universal leukoreduction in the United States. On the other hand, the year saw the publication of several pivotal clinical trials that failed to demonstrate significant patient benefit from the use of leukoreduced blood components. The emerging scientific and clinical evidence reviewed in this article demonstrates that leukoreduction technology is an effective means to reduce the risk of three complications of transfusion: HLA alloimmunization, cytomegalovirus transmission, and recurrent febrile nonhemolytic transfusion reactions. The application of the technology to all blood components does not appear to be warranted.

A parallel evaluation of four automated hematology analyzers

A parallel evaluation was performed on four automated hematology analyzers: the Celldyn 3000 (Unipath Corp., Mountain View, CA), the Coulter STKS (Coulter Electronics Inc., Hialeah, FL), the Sysmex NE-8000 (Baxter Healthcare Corp., McGaw Park, IL), and the Technicon H*2 (Miles Corp., Tarrytown, NY). The protocol included evaluation of the complete blood count and differential leukocyte count (DLC) parameters. The DLC evaluation was performed using the National Committee for Clinical Laboratory Studies H20-A protocol. Based on this evaluation, the authors could not identify a single instrument that was clearly superior to the others. Overall, the four instruments were found to be safe and effective for diagnostic use; however, there were areas in which their performance was less than optimal. Particular questions were raised regarding the clinical usefulness of instrumental "flags" to identify qualitative leukocyte abnormalities. The results are discussed in relation to the selection of instruments for specific clinical applications.

Validation of use of the Nageotte hemocytometer to count low levels of white cells in white cell-reduced platelet components

BACKGROUND

Determination of the white cell (WBC) count in WBC-reduced platelet components requires methods that have a detection limit in the range of approximately 5.0 x 10(2) to 5.0 x 10(4) per mL.

STUDY DESIGN AND METHODS

With a 50-microL Nageotte hemocytometer and bright-field microscopy (200x magnification), studies were conducted to develop and validate a method that could be used routinely with filtered and apheresis-harvested platelets. A 1-in-5 dilution of sample with a commercially available blood-diluting fluid was used because, with a lower (1-in-2) dilution, the observed number of WBCs was substantially less than the number expected at relatively high platelet counts (> 1.9 x 10(9)/mL).

RESULTS

The observed and expected WBC counts in WBC-reduced platelet samples correlated well at levels between approximately 5 and 1100 WBCs per counting area (5.0 x 10(2)-1.1 x 10(5)/mL). At levels of more than 300 to 400 WBCs per counting area, accurate counts were obtained when 10 of the 40 rectangles were counted.

CONCLUSION

These studies provide data to confirm that the 50-microL Nageotte hemocytometer can be used to accurately count low levels of WBCs in platelet components.

A multicenter study evaluating three methods for counting residual WBCs in WBC-reduced blood components: Nageotte hemocytometry, flow cytometry, and microfluorometry

BACKGROUND

A multicenter study was conducted to evaluate the performance characteristics of flow cytometry and microfluorimetry for counting low concentrations of WBCs and to compare the results with Nageotte hemocytometry.

STUDY DESIGN AND METHODS

A two-phase study involving 10 centers located in the United States and in Europe was performed. Coded samples of RBCs and platelets were distributed by 24-hour (Phase 1) or 2-day (Phase 2) courier service to each test site for analysis. Samples were prepared to include concentrations of WBCs slightly above and below the concentration corresponding to the threshold standards for WBC-reduced RBCs and platelets. All centers tested samples by Nageotte hemocytometry plus one or both of two automated methods.

RESULTS

Both flow cytometry and microfluorometry gave better results than Nageotte hemocytometry in testing freshly prepared samples. At WBC concentrations >5 per microL (RBCs) or >3 per microL (platelets), the intersite CV was <20 percent for the automated methods but >30 percent for the Nageotte hemocytometer method (p<0.001). Accuracy was greater for the automated methods than for the Nageotte hemocytometer method (p<0. 001). Nageotte hemocytometry showed a bias to underestimation relative to the results obtained with the automated methods. All methods had poorer performance in testing samples that required > or =2 days' shipment than in testing of those requiring overnight shipment.

CONCLUSION

Automated methods for counting residual donor WBCs in WBC-reduced cellular components offer advantages of improved precision and greater accuracy than are seen with the Nageotte hemocytometer method. Automated methods are less labor-intensive but more costly than microscopic methods. Preparation and shipping methods will need further refinement for samples to be counted more than 24 hours after sample collection.

Automated counting of white blood cells in synovial fluid

OBJECTIVES

To evaluate the performance of automated leucocyte (white blood cell; WBC) counting by comparison with manual counting.

METHODS

The number of WBC was determined in heparinized synovial fluid samples by the use of (i) a standard urine cytometer (Kova) and a microscope (reference method) and (ii) a haematology analyser (Sysmex XE-2100; WBC/BASO and DIFF channels). Imprecision within and between days was determined by replicate analysis of a low (level A; WBC approximately 0.560 x 10(9)/l) and a high (level B; WBC approximately 1.081 x 10(9)/l) dedicated synovial fluid control (Quantimetrix).

RESULTS

The WBC count of the DIFF channel was highly correlated with the WBC count of the microscopic reference method (r = 0.99; WBC analyser = 0.870 x WBC reference method + 0.413). In contrast, no agreement existed between WBC counts generated by the WBC/BASO channel of the analyser and the reference method (r = 0.52; WBC analyser = 0.008 x WBC reference method + 0.079). Within-day imprecision (4-7%) and between-day imprecision (10%) of the haematology analyser were smaller than the within-day imprecision (12%) and the between-day imprecision (20-22%) of the manual reference method. For manual counting, inter-observer coefficients of variation were 35.9% (control level A) and 21.0% (control level B).

CONCLUSIONS

The WBC count in synovial fluid can be reliably determined using the DIFF channel of the Sysmex XE-2100. Automated counting of WBC in synovial fluid offers more precise and faster results than manual counting.

European Multi-Center Evaluation of the Abbott Cell-Dyn Sapphire Hematology Analyzer

This study presents the results of performance evaluations of the Cell-Dyn Sapphire (CD-Sapphire) undertaken by 3 study sites in Europe. These studies focused on the routine blood count analyses with specific consideration of precision and imprecision, linearity, inter-instrument correlations, and white blood cell differential and flagging efficiencies. The CD-Sapphire was compared to the Cell-Dyn CD4000, Bayer Advia 120, Beckman Coulter GenS, and reference microscopy.

Comparison of white blood cell differential percentages determined by the in-house LaserCyte hematology analyzer and a manual method

BACKGROUND

The LaserCyte hematology analyzer (IDEXX Laboratories, Chalfont St. Peter, Bucks, UK) is the first in-house laser-based single channel flow cytometer designed specifically for veterinary practice. The instrument provides a full hematologic analysis including a 5-part WBC differential (LC-diff%). We are unaware of published studies comparing LC-diff% results to those determined by other methods used in practice.

OBJECTIVE

To compare LC-diff% results to those obtained by a manual differential cell count (M-diff%).

METHODS

Eighty-six venous blood samples from 44 dogs and 42 cats were collected into EDTA tubes at the Forest Veterinary Centre (Epping, UK). Samples were analyzed using the LaserCyte within 1 hour of collection. Unstained blood smears were then posted to Langford Veterinary Diagnostics, University of Bristol, and stained with modified Wright's stain. One hundred-cell manual differential counts were performed by 2 technicians and the mean percentage was calculated for each cell type. Data (LC-diff% vs M-diff%) were analyzed using Wilcoxon signed rank tests, Deming regression, and Bland-Altman difference plots.

RESULTS

Significant differences between methods were found for neutrophil and monocyte percentages in samples from dogs and cats and for eosinophil percentage in samples from cats. Correlations (r) (canine/feline) were .55/.72 for neutrophils, .76/.69 for lymphocytes, .05/.29 for monocytes and .60/.82 for eosinophils. Agreement between LC-diff% and Mdiff% results was poor in samples from both species. Bland-Altman plots revealed outliers in samples with atypical WBCs (1 cat), leukocytosis (2 dogs, 9 cats), and leukopenia (16 dogs, 11 cats). The LaserCyte generated error flags in 28 of 86 (32.6%) samples, included 7 with leukopenia, 8 with lymphopenia, 7 with leukocytosis, 1 with anemia, and 1 with erythrocytosis. When results from these 28 samples were excluded, correlations from the remaining nonflagged results (canine/feline) were .63/.65 for neutrophils, .67/.65 for lymphocytes, .11/.33 for monocytes, and .63/.82 for eosinophils.

CONCLUSION

Although use of a 100-cell (vs 200-cell) M-diff% may be a limitation of our study, good correlation between WBC differentials obtained using the LaserCyte and the manual method was achieved only for feline eosinophils.

Evaluation of ADVIA 120 CSF assay (BayerR) vs. chamber counting of cerebrospinal fluid specimens

The ADVIA 120 cerebrospinal fluid (CSF) assay (Bayer; Bayer Corp., Tarrytown, NY, USA) provides a new, automated analysis of CSF specimens. We evaluated this method by comparing its performance with classic chamber counting and microscopic analysis of CSF samples.

A field evaluation of the Coulter STKS

The performance of the Coulter STKS (Coulter, Hialeah, FL) was evaluated in a busy computerized teaching hospital laboratory. The STKS was compared with a Coulter S Plus IV and manually performed 400 white blood-cell differentials. The measured blood-count parameters (i.e., white blood cells [WBCs], red blood cells [RBCs], hemoglobulin [Hb], mean corpuscular volume [MCV], and platelets [PLTs]), compared very well between the two aperture impedance-based systems; precision, linearity, and lack of carryover were excellent. The STKS WBC differential (DIFF), derived from a combination of aperture impedance, aperture conductance, and laser light scatter, also was precise; linear and carryover were insignificant. The DIFFs (n = 424) compared well to the manual WBC differentials, with r values of 0.97, 0.97, 0.73, and 0.86 for neutrophils, lymphocytes, monocytes, and eosinophils, respectively. The DIFF and Suspect Flagging system produced 6.2% false negatives and 2.6% false positives when compared with the manual technique. These were further investigated and discussed. STKS DIFFs were stable for 18 to 24 hours in normal samples anticoagulated with K2EDTA and stored at 20 degrees C prior to analysis. Storage in the same anticoagulant at 4 degrees C and immediate aspiration preserved the DIFF analysis for considerably longer than 24 hours. These performance characteristics make the STKS a significant advancement in automated hematology.

Immature granulocyte measurement using the Sysmex XE-2100. Relationship to infection and sepsis

We determined the usefulness of immature granulocyte measurement as a predictor of infection or positive blood culture and compared the results with total WBC count and absolute neutrophil count (ANC). Blood samples from 102 infected and 69 noninfected patients were analyzed using the Sysmex XE-2100 automated blood cell counter (Sysmex, Kobe, Japan). The percentage of immature granulocytes was significantly higher in infected than in noninfected patients and in patients with positive than patients with negative blood cultures. Receiver operating characteristic curves showed that the percentage of immature granulocytes was a better predictor of infection than the WBC count and comparable to the ANC. Automated immature granulocyte measurements reflect a biologically and clinically relevant phenomenon but are not sensitive enough to be used as screening assays for prediction of infection or bacteremia. However, although infrequently encountered, a percentage of immature granulocytes of more than 3 was a very specific predictor of sepsis and might help expedite microbiologic laboratory evaluation of a subset of patients.

Precision and accuracy of absolute lymphocyte counts

A critique of leukocyte counting using automated hematology instruments is presented. Important preanalytical variables include the anticoagulant and specimen assay delays. The precision of counts is directly related to the number of leukocytes counted. Criteria for the selection of an acceptable hematology laboratory for lymphocyte counts for CD4 determinations are presented.

Utility of a peritoneal dialysis leukocyte test strip in the diagnosis of peritonitis

Expeditious diagnosis of peritonitis remains a significant goal in the management of patients maintained on peritoneal dialysis. Several attempts to use leukocyte esterase reagent strips to diagnose peritonitis have been described. In this study we examined the usefulness of a new reagent strip, the PeriScreen Test Strip, in the diagnosis of peritonitis. A series of 72 peritoneal effluent samples obtained from 22 maintenance peritoneal dialysis patients is reported. In this study, the test strips had a sensitivity of 100% and a specificity of 98.3% as compared to an abnormal leukocyte count. Thus, in the diagnosis of peritonitis we believe that the PeriScreen Test Strip can be used as a simple bedside screening test to exclude peritonitis in peritoneal dialysis patients.