will cella vision kill the blood film star

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  1. 1. Automated systems within clinical laboratories aim to increase theThe laboratory scientists were selected with differing experience in bloodThe classification of the red blood cells was less successful, withefficiency of reporting patient results. The results from analysers used cell morphology; two were highly experienced, one moderately the instrument reporting macrocytosis and anisocytosis on manyfor blood cell counting and white blood cell differentiation may experienced, and two newly qualified whom may still require assistance samples that had normal red blood cells. However in 95% ofsometimes need to be verified by a manual blood film reviewin the laboratory with very abnormal blood films.samples, the quality of red cell images was sufficient for theespecially, if there are atypical, immature cells or nucleated red bloodoperator to clearly identify morphological features and reclassifycells present. METHOD the results. (Figure 2) In this evaluation, the default red cell pre-Figure 1. CellaVision DM96characterisation setting was used, which may have contributed to Thirty films were presented to the scientists, firstly for classification on the disagreement; settings can be adjusted by the operator to the DM96, then to perform their own 100 cell manual differential on aachieve a level of classification equivalent to that by manual light microscope. No clinical information or history, nor haematologymicroscopy. The overall accuracy of the manual differentials by the analyser results were available to the scientists. The 100 cell manual five different operators did not exceed that of the DM96. This was differentials for each individual were compared to the result for the pre- demonstrated by the comparison of each individuals manual classified, and then their re-classified cells from the DM96, anddifferential as well as their pre- and reclassified differentials from additionally all results compared to the reference cell differential. Thethe DM96 to the reference method. time taken for the differentials from the CellaVision and manual method were recorded for each individual. For some cell types and for some operators, the accuracy of theDM96 compared to the reference method was better than that of theindividuals 100 cell manual differential. Correlation with the RESULTSreference method for the lymphocyte count from the reclassifiedresults from the DM96 is very poor for one of the inexperienced The resulting percentage of the various cell classes pre-classifiedoperators this is due to a single sample where the DM96 pre- correctly by the DM96 was highest for mature cells and lowest forclassified lymphocytes were not correctly reclassified as blasts.. metamyelocytes and promyelocytes. There was good classification of Correlation for the eosinophils on the DM96 was not as good as the nucleated red blood cells (table 1)..manual method (R2 0.60) even after reclassification. This may beattributed to a staining issue, where eosinophils appear more pinkon the DM96 than under a microscope. Table 1. Statistically, the pre-classification results on the DM96 forManual blood film examination is costly both in a financial and lymphocytes, immature granulocytes, myelocytes and to a lessertime sense. With patient result turnaround times of utmost importance extent basophils, had significantly higher values than those by theto any clinical laboratory, the time taken to perform manualreference method, reclassified results or each operators manualdifferentials means the biomedical scientist is unable to perform other differential. The DM96 had a tendency to classify other cells intoroutine duties within the laboratory. these classes. For reclassified cells there were very few statisticallysignificant differences identified between the specific users manualThis study was undertaken to compare the speed, efficiency anddifferential and the DM96 when compared to the reference method.accuracy of an automated film reader, namely the CellaVision DM96 The greatest number of statistically significant differences occurred(CellaVision AB Lund Sweden) to biomedical scientists.again with lymphocytes and basophils; basophils attributed to bythe low number of cells counted.The CellaVision DM96 consists of a slide-scanning unit and aFor lymphocytes the median range for reclassified cells on thecomputer with the CellaVision Blood differential Software (VersionDM96 is 1.20 1.42 x109/L, for the manual differentials 1.07 1.521.5). The scanning unit consists of a motorised microscope (10x, 50x, x109/L and for the reference method count was 1.42 x109/L. Theand 100x objective) and a digital CCD camera. The instrument can be highly experienced operators showed better statistical agreementloaded with eight racks of twelve slides, continuously fed into the between the manual and DM96 differentials.analyser, processing them immediately. The DM96 scans the slides,identifies potential WBCs, takes digital images of them and uses an The total time required for the pre-classification andartificial neural network-based software to analyse the cells. Digitalreclassification on the DM96 for the thirty blood films was similarimages of the pre-classified cells are presented to the operator on a userfor all operators, averaging 80 minutes for all scientists, regardlessdefinable computer display. The operator is then able to re-classify theof their experience. The manual differential required a greatercells by double clicking or dragging the images to the group of cells toamount of time, the quickest being 100 minutes, with thewhich it belongs. Cells can also be magnified with simple mouse inexperienced scientists taking significantly longer (table 3).movements to allow finer cellular examination. All pre-classified cellshave to be examined by the user and re-classified if necessary beforeAssessment of the accuracy of the DM96s pre-classification versusdata is saved and authorisation is allowed. The DM96 also partiallyreclassification of results was carried out by determining the correlationclassifies red blood cell morphology; polychromasia, hypochromia,coefficient (R2) between the reference manual differential and the pre-Table 3.macrocytosis, anisocytosis and poikilocytosis reported on a scale of 0 and re-classified results from the DM96 for all cell classes. Correlationto 3.coefficients were higher after the cells had been re-classified, where R2 values were greater than 0.9 for all cells except monocytes (0.81) andFigure. 2 Screenshot of evaluation of red blood cells on DM96eosinophils (0.67). Due to the low number and subjectivity of classification of metamyelocytes, myelocytes and promyelocytes, the results for these cells were also reported as a total immature granulocyte count. Poor correlation for the individual immature granulocytes was attributed to the low number of cells counted and the subjectivity of classification into each maturity class. Correlation for the total immature granulocytes was excellent. Figure 3 demonstrates correlation graphs for Figure 4. Screen shot of cells presented for reclassification on the the immature granulocytes, nucleated red blood cells and blasts..DM96 Figure 3.This study aims to evaluate the accuracy of the DM96 in identifyingall classes of leucocytes including abnormal and immature cells.Results from five different laboratory scientists manual differentialsand those from the DM96 were compared to a standard referencemanual differential (Clinical and Laboratory Standards Institute H20-A2, 2007) and the time taken for the slides analysis, recorded. Alimited evaluation of the red cell morphology from the DM96 was alsoundertaken. So can the an instrument ever replace the laboratory scientistsmanual differentiation?REFERENCE METHOD For any automated image system to be introduced in theThe reference method was a 200 cell manual differential count haematology laboratory it would have to demonstrate that it couldperformed by two experienced laboratory scientists using lightreliably and correctly identify WBCs. Though the DM96 is capablemicroscopy. The DM96 was set to count 105 cells to counter theof morphological classification of cells, its accuracy depends oneffects of artefacts, although 100 cells was not always achieved due to both the blood pathology and the experience of the scientist. Forsome samples having very low WBC counts. Two thirds of thesome cell types and for some operators, the DM96s accuracy wasreference films were abnormal with various clinical conditions such asbetter than the individuals 100 cell manual differential. It is also a