Standardisation of platelet counting accuracy in blood banks by reference to an automated immunoplatelet procedure: comparative evaluation of Cell-Dyn CD4000 impedance and optical platelet counts

Compare the accuracy and precision of Coulter LH780, Mindray BC-6000 Plus, and Sysmex XN-9000 with the international reference flow cytometric method in platelet counting

Objective

The aim of this study is to evaluate the performance of different platelet counting methods (optical, impedance, fluorescence and hand counting) applied in different analysers by comparing with the international flow cytometric reference method (IRM).

Methods

A total of 333 blood samples from different subgroups (168 cases with thrombocytopenia, 136 cases with normal platelet counts and 29 cases with thrombocytosis) were tested. Regarding IRM as the gold standard, we compared the accuracy and precision of different platelet count methods; i.e. LH780 (impedance), BC-6000 Plus (optical (O) and impedance (I)), Sysmex XN-9000 (optical (O), impedance (I), fluorescence (F)), and hand counting.

Results

Sysmex XN-9000-F (r = 0.988) had the best correlation with IRM for thrombocytopenic samples; BC-6000 Plus-I (r = 0.966) was more relevant to IRM than any other method for samples with normal platelet counts. Correlation between Sysmex XN-9000-I (r = 0.960) and IRM was the highest among these methods for samples with thrombocytosis. For bias evaluation, the average bias of Sysmex XN-9000-F was -1.5 × 10⁹/L (95% LA = -9.4 to +6.4) for samples with thrombocytopenia, compared with IRM. BC-6000 Plus-I had a small mean difference with IRM for samples with normal platelet counts or thrombocytosis. Moreover, all evaluated methods had acceptable sensitivity, specificity, and concordance rates as compared with IRM in the diagnosis of thrombocytopenia and thrombocytosis.

Conclusions

Platelet counting by Sysmex XN-9000-F is more accurate than other methods for thrombocytopenic samples. BC-6000 Plus-I has superior association and consistency for normal platelet counts. As for thrombocytosis patients, Sysmex XN-9000-I has the highest correlation with IRM while Sysmex XN-9000-O has the highest diagnosis efficacy.

Effect of adhesive properties of buffy coat on the quality of blood components produced with Top & Top and Top & Bottom bags

BACKGROUND

The Transfusion Medicine Unit of Reggio Emilia currently collects whole blood using conventional quadruple Fresenius Top & Top bags. In this study, new Fresenius Top & Bottom bags were assessed and compared to the routine method with regards to product quality and operational requirements.

MATERIAL AND METHODS

Twenty-one whole blood units were collected with both the new and the traditional bags, and then separated. Quality control data were evaluated and compared in order to estimate yield and quality of final blood components obtained with the two systems. We collected other bags, not included in the ordinary quality control programme, for comparison of platelet concentrates produced by pools of buffy coat.

RESULTS

Compared to the traditional system, the whole blood units processed with Top & Bottom bags yielded larger plasma volumes (+5.7%) and a similar amount of concentrated red blood cells, but with a much lower contamination of lymphocytes (-61.5%) and platelets (-86.6%). Consequently, the pooled platelets contained less plasma (-26.3%) and were significantly richer in platelets (+17.9%).

DISCUSSION

This study investigated the effect of centrifugation on the adhesiveness of the buffy coat to the bag used for whole blood collection. We analysed the mechanism by which this undesirable phenomenon affects the quality of packed red blood cells in two types of bags. We also documented the incomparability of measurements on platelet concentrates performed with different principles of cell counting: this vexing problem has important implications for biomedical research and for the establishment of universal product standards. Our results support the conclusion that the Top & Bottom bags produce components of higher quality than our usual system, while having equal operational efficiency. Use of the new bags could result in an important quality improvement in blood components manufacturing.

Accuracy of platelet counting by automated hematologic analyzers in acute leukemia and disseminated intravascular coagulation: potential effects of platelet activation

Platelet counting in patients with acute leukemia or disseminated intravascular coagulation (DIC) may have a risk for erroneous counts owing to the presence of nonplatelet particles or platelet activation. We evaluated automated platelet counting methods using the Abbott Cell-Dyn Sapphire (Abbott Diagnostics, Santa Clara, CA), Sysmex XE-2100 (Sysmex, Kobe, Japan), ADVIA 2120 (Siemens Diagnostics, Tarrytown, NY), and Beckman Coulter LH 750 (Beckman Coulter, Miami, FL) compared with the international reference method (IRM). Automated platelet counting methods were inaccurate compared with the IRM, without evidence of interfering nonplatelet particles. It is interesting that platelet activation markers were associated with DIC severity and erroneous platelet counting, suggesting that platelet activation is a potential source of inaccuracy. Furthermore, the artifactual in vitro platelet activation induced a high degree of intermethod variation in platelet counts. The inaccuracy of automated platelet counts increased the risk for misdiagnosis of DIC. More attention needs to be given to the accuracy of platelet counts, especially in clinical conditions with florid platelet activation.

The influence of conditions utilized to hold apheresis and whole blood-derived platelet samples before platelet enumeration with three hematology analyzers

BACKGROUND

The Advia 120 (Siemens Diagnostics) hematology analyzer is different from other hematology analyzers in that it requires platelets (PLTs) to be "effectively spherical" to be counted. Our study evaluated how PLT counts with this hematology analyzer and two other models were influenced by the holding of PLT product samples.

STUDY DESIGN AND METHODS

Samples were prepared from apheresis PLT products (APs) collected in ACD-A and from whole blood-derived PLT concentrates (PCs) in CP2D or ACD-A. Samples were stored in K(2) and K(3) ethylenediaminetetraacetate (EDTA) tubes at room temperature (RT) and in the cold. PLT counts were determined immediately, after 1 and 4 hours, and after an overnight hold, using Advia 120, XE-2100D, and Cell-Dyn 3700 hematology analyzers.

RESULTS

A time-dependent increase in PLT counts was observed with AP samples held at RT using the Advia 120, but not with the other two hematology analyzers. AP samples held in the cold did not show a substantial time-dependent increase with any of the hematology analyzers. With the Advia 120, the PLT counts in the immediate samples were approximately 14% lower compared to those in cold or overnight-held RT samples. PC samples with all holding conditions and hematology analyzers did not show any substantial time-dependent increase in counts.

CONCLUSIONS

With the Advia 120 hematology analyzer, the time-dependent increase in PLT counts with RT-held samples may be related to the need to have effectively sphered PLTs unlike that with the other two hematology analyzers. The absence of a holding effect with PC samples may indicate that only AP samples have population(s) that are slow to convert to spherical PLTs.

Performance of automated platelet quantification using different analysers in comparison with an immunological reference method in thrombocytopenic patients

BACKGROUND

Rapidly available and accurate platelet counts play an important role in the evaluation of haemorrhagic status and in assessing the need for platelet transfusions. We, therefore, evaluated platelet counting performance of haematology analysers using optical, impedance and immunological methods in thrombocytopenic patients.

MATERIALS AND METHODS

We considered 99 patients with a platelet (plt) count under 50 x 10(9) plt/L. We compared the platelet counts obtained using ADVIA 2120 (optical method), Cell-Dyn Sapphire (optical, impedance and immunological methods with CD61) and a reference, double staining (CD41+CD61) immunological method.

RESULTS

The platelet counts of all the considered methods showed good correlation with those of the reference method, despite an overestimation in platelet quantification. The degree of inaccuracy was greater for platelet counts under 20 x10(9) plt/L.

CONCLUSIONS

Clinicians who use platelet thresholds below 20 x10(9) plt/L for making clinical decisions must be aware of the limitations in precision and accuracy of cell counters at this level of platelet count. Inaccurate counts of low platelet numbers could create problems if attempts are made to reduce the threshold below 20 x 10(9) plt/L.

Counting platelets in platelet concentrates on hematology analyzers: a multicenter comparative study

BACKGROUND

Hematology analyzers are designed to count whole blood samples, but are also used by blood centers to perform quality control on blood components. In platelet (PLT) concentrates, the number of PLTs is approximately fivefold higher and red blood cells are absent, causing variable PLT counting results. It was our aim to compare currently used hematology analyzers for counting PLTs in PLT concentrates using fixed human PLTs.

STUDY DESIGN AND METHODS

PLT samples were fixed, diluted into seven concentration levels (plus one blank), aliquoted, and shipped to 68 centers. Evaluable data were obtained for 89 hematology analyzers. All samples were counted six times, and results were reported to the coordinating center. The overall group mean was calculated, and the percentage deviation from this mean was calculated for each analyzer.

RESULTS

At PLT levels relevant for blood centers, 750 x 10(9) to 2000 x 10(9) per L, analyzers gave results that were between 35 percent lower and 16 percent higher than the overall group mean. Within a group of analyzers, results were comparable with coefficient of variations usually below 10 percent, indicating that the observed differences were caused by instrument characteristics. A smaller study with fresh, unfixed PLT samples showed that analyzers behaved similarly for fixed and fresh PLTs.

CONCLUSION

With a wide array of currently used hematology analyzers, a marked difference was determined for the PLT counts of fixed human-based identical samples provided to 68 laboratories by a centralized facility. A gold standard method is needed to allow for more valid interlaboratory comparisons between hematology analyzers.

In vitro evaluation of platelet concentrates during storage: Platelet counts and markers of platelet destruction

BACKGROUND

Differences in platelet counts are observed by use of automated haematology analyzers making interlaboratory comparison difficult.

MATERIALS AND METHODS

Twenty-eight single-donor platelet concentrates (PCs) were collected. Platelet concentration and markers of platelet destruction were investigated during storage for 11/12 days.

RESULTS

Increasing impedance-immunoplatelet ratio was observed during storage, correlating to platelet fragments, large platelets, platelet density and cell-lysis. High variability was observed for optical-immunoplatelet ratio.

CONCLUSION

Immunoplatelet count or correction factor calculated by impedance-immunoplatelet ratio should be used to confirm that platelet unit meets platelet count requirements or to compare results from clinical trials. Optical platelet count is not recommended.

Platelet counting in platelet concentrates with various automated hematology analyzers

BACKGROUND

Hematology analyzers use impedance, optical, and/or immunologic techniques for counting platelets (PLTs). PLT counting in whole blood has been validated thoroughly; however, this is not the case for PLT counting in PLT concentrates (PCs), in which red cells (RBCs) are absent. Therefore, this study is focused on PLT counting in PCs to study use of ethylenediaminetetraacetate (EDTA), carryover, and accuracy of the analyzers.

STUDY DESIGN AND METHODS

In total six hematology analyzers (AcT 8, Beckman Coulter; ADVIA 2,120, Bayer; Cell-Dyn 4,000, Abbott; Onyx, Beckman Coulter; K4,500, Sysmex; and XT 2,000i, Sysmex) were tested for PLT counting. PC samples with various PLT concentrations were made (0-1,700 x 10(9)/L) and measured 10 times. Carryover was determined five times.

RESULTS

PC samples (1,000 x 10(9) PLTs/L) in EDTA tubes showed significantly higher PLT counts than samples in "dry" tubes for all analyzers except for the Cell-Dyn 4,000 with the impedance technique. Carryover was not more than 0.3 percent for all analyzers. The K4,500 showed the most accurate results, whereas the Cell-Dyn 4,000 with the impedance technique had low accuracy due to an overestimation of more than 20 percent.

CONCLUSION

Most tested analyzers seemed to be suitable for counting PLTs in PCs. All hematology analyzers should be validated for counting PLTs in absence of RBCs as is the case in PCs, in addition to validation of PLT counting in whole blood.

Clinical effect of buffy-coat vs. apheresis platelet concentrates in patients with severe thrombocytopenia after intensive chemotherapy

BACKGROUND AND OBJECTIVES

Therapeutic or prophylactic use of platelet concentrates (PC) is essential for patients with thrombocytopenia due to intensive chemotherapy for various malignancies. PC quality has been improved after introduction of storage containers that are more oxygen permeable than the second-generation PC containers. Consequently, shelf life of PCs at our blood bank has been extended to 6.5 days after monitoring each PC for bacterial contamination. In this prospective observational study, we compared apheresis PCs harvested by Amicus cell separator with buffy-coat (BC) PCs during storage for up to 6.5 days.

MATERIALS AND METHODS

All PCs were collected from healthy volunteer donors and were prepared for routine clinical use. A total of 446 transfusion episodes with 688 PCs for 77 adult patients with oncological and haematological diseases were registered during a 13-month period. Outcome measures were corrected count increment after 1 h (CCI-1), after 18-24 h (CCI-2), and transfusion intervals. Transfusions were carried out after storage from 1.5 to 6.5 days.

RESULTS

Both CCI and the transfusion intervals decreased statistically significantly by increasing storage time after transfusions with apheresis PCs or BC PCs. However, less than 4% of the variation in CCI and transfusion interval could be explained by platelet storage time. There were no significant differences between BC PCs and apheresis PCs, regarding CCI and transfusion intervals.

CONCLUSION

We can conclude that BC PCs are not inferior to apheresis PCs, and may serve the clinical purposes as well as apheresis PCs harvested by Amicus.

Platelets in the paediatric population: the influence of age and the limitations of automation

Accurate and precise platelet counting is important for the clinical management of children with platelet disorders. Current automated technologies are often unable to discriminate platelets from non-platelet particles particularly in circumstances where platelet anisocytosis is common. This study compares manual methodology and the automated technologies; impedance, optical density and CD61 immunoplatelet method (available on the Cell Dyn 4000) with the reference method of flow cytometric analysis in a paediatric population. A total of 141 samples were analysed and divided into specific age related groups and groups with thrombocytopenia and thrombocytosis. Data analysis showed that the CD61 method compared best with the reference method and this was evident in all the specified groups. The mean platelet count obtained by optical and manual methods were lower, suggesting that these methods are less reliable. The impedance count method was accurate despite its limitations. Strong correlations were observed in the 2-14 year age group but there was greater variation in the <1 month group supporting the theory that there is a greater variation in platelet characteristics in neonates. The CD61 method is the automated method of choice and would be particularly useful in the problem groups (platelet counts <50 x 10(9)/l and neonates <1 month old).

The platelet count accuracy of platelet concentrates obtained by using automated analysis is influenced by instrument bias and activated platelet components

BACKGROUND AND OBJECTIVES

The blood platelet content (in numbers) of platelet concentrates is required for production quality control and to predict clinical responses.

MATERIALS AND METHODS

This study compared the performance of automated counting from impedance and optical instruments to data from immunoplatelet reference analysis.

RESULTS

All methods showed good linearity with evidence of significant instrument-specific deviations from the line of agreement. Relational formulae largely corrected bias, but did not resolve platelet count variability. A second confounding factor, related to the proportion of small (activated) platelets, was also shown to contribute to intermethod discrepancies.

CONCLUSIONS

Blood processing centres should establish correction factors for each instrument compared to reference methods, such as the immunoplatelet count.