Correction of spurious low platelet counts by optical fluorescence platelet counting of BC-6800 hematology analyzer in EDTA-dependent pseudo thrombocytopenia patients

Integration of an MC-80 Digital Image Analyzer With an Automated BC-6800Plus Hematology Analyzer Enables Accurate Platelet Counting in Samples With EDTA-Induced Pseudothrombocytopenia

Background

EDTA-induced pseudothrombocytopenia (PTCP) during whole blood collection requires significant laboratory resources to obtain accurate results. We evaluated platelet-deaggregation function in EDTA-induced PTCP and platelet-clump flagging by the BC-6800Plus hematology analyzer using integrated digital image analysis.

Methods

We prospectively collected 132 whole blood samples suspected of platelet clumping (102 in EDTA and 30 in sodium citrate) from 88 individuals. We compared platelet counts determined using the platelet count by impedance (PLT-I) function of the DxH 900 hematology analyzer and the PLT-I or optical platelet count (PLT-O) function of the BC-6800Plus. Platelet clumping was verified through manual inspection and the MC-80 digital image analyzer.

Results

Among the 132 whole blood samples, 43 EDTA samples showed platelet clumping. The DxH 900 PLT-I and BC-6800Plus PLT-I results demonstrated a strong correlation (r=0.711) for the EDTA samples but only a moderate correlation with the BC-6800Plus PLT-O results (r=0.506 and 0.545, respectively). The BC-6800Plus PLT-O results were consistent with the sodium citrate platelet counts, with a median dissociation rate of 102.5% (range, 74.9%-123.1%). The DxH 900 and BC-6800Plus analyzers had sensitivity values of 0.79 and 0.72, respectively, for platelet-clump flagging. When integrating the MC-80 digital image analysis results, the sensitivity of BC-6800Plus improved to 0.89 (standard mode) or 1.0 (PLT-Pro mode).

Conclusions

BC-6800Plus PLT-O measurement results are close to the actual values obtained by platelet deaggregation with PTCP samples. Integrating the BC-6800Plus with a digital imaging analyzer effectively improved the diagnosis of PTCP and reduced the requirement for additional laboratory procedures.

National recommendations of the Croatian Chamber of Medical Biochemists and Working group for Laboratory hematology of the Croatian Society of Medical Biochemistry and Laboratory Medicine: Management of samples with suspected EDTA-induced pseudothrombocytopenia

Pseudothrombocytopenia (PTCP) is defined by the occurence of spouriously low platelet count as a consequence of in vitro platelet aggregation. It is a rare and benign artifact, not associated with any specific disorder or therapy, that becomes clinically relevant when it is not timely and reliably recognized. Thus, it may result in inappropriate clinical decisions (i.e. unnecessary further testing, misdiagnoses and potential patients' mismanagement) unavoidably compromising patient safety. The most common form of PTCP is caused by ethylenediaminetetraacetic acid (EDTA). Several approaches for the management of samples with EDTA-induced PTCP have been described in the literature. However, expert recommendations are scarce. The scope of these recommendations is to assist in achieving national harmonisation in laboratory management (i.e. detecting and reporting platelet counts) of samples with EDTA-induced PTCP. These minimal recommendations were prepared by the members of the joint working group of the Croatian Chamber of Medical Biochemists and Working group for Laboratory Hematology of the Croatian Society of Medical Biochemistry and Laboratory Medicine, and might be customized according to specific conditions (i.e. personnel and equipment) of each individual laboratory. These recommendations are primarily intended to all laboratory professionals involved in the management of samples with EDTA-induced PTCP, but also to other healthcare professionals involved in collecting samples and interpreting complete blood count results.

Construction of platelet count-optical method reflex test rules using Micro-RBC#, Macro-RBC%, "PLT clumps?" flag, and "PLT abnormal histogram" flag on the Mindray BC-6800plus hematology analyzer in clinical practice

OBJECTIVES

Utilizing RBC or PLT-related parameters to establish rules for the PLT-O reflex test can assist laboratories in quickly identifying specimens with interfered PLT-I that require PLT-O retesting.

METHODS

Prospective PLT-I and PLT-O testing was performed on 6857 EDTA-anticoagulated whole blood samples, split randomly into training and validation cohorts at a 2:3 ratio. Reflex and non-reflex groups were distinguished based on the differences between PLT-I and PLT-O results. By comparing RBC and PLT parameter differences and flags in the training set, we pinpointed factors linked to PLT-O reflex testing. Utilizing Lasso regression, then refining through univariate and multivariate logistic regression, candidate parameters were selected. A predictive nomogram was constructed from these parameters and subsequently validated using the validation set. ROC curves were also plotted.

RESULTS

Significant differences were observed between the reflex and non-reflex groups for 19 parameters including RBC, MCV, MCH, MCHC, RDW-CV, RDW-SD, Micro-RBC#, Micro-RBC%, Macro-RBC#, Macro-RBC%, MPV, PCT, P-LCC, P-LCR, PLR,"PLT clumps?" flag, "PLT abnormal histogram" flag, "IDA Anemia?" flag, and "RBC abnormal histogram" flag. After further analysis, Micro-RBC#, Macro-RBC%,"PLT clumps?", and "PLT abnormal histogram" flag were identified as candidate parameters to develop a nomogram with an AUC of 0.636 (95 %CI: 0.622-0.650), sensitivity of 42.9 % (95 %CI: 37.8-48.1 %), and specificity of 90.5 % (95 %C1: 89.6-91.3 %).

CONCLUSIONS

The established rules may help laboratories improve efficiency and increase accuracy in determining platelet counts as a supplement to ICSH41 guidelines.

Performance evaluation of PLT-H (hybrid-channel platelet) under various interferences and application studies for platelet transfusion decisions

The hybrid-channel platelet counting method (PLT-H) is a new platelet counting technique proposed by Mindray of China. In this study, we aimed to evaluate the accuracy of this technique in various situations and its reliability in platelet transfusion decision-making. A total of 378 venous blood samples were tested. Using the immunological PLT counting method recommended by the International Council for Standardization in Hematology as the reference method (PLT-IRM), Passing-Bablok regression and Bland-Altman analysis were performed on the PLT-H results. The anti-interference performance of PLT-H under different interference levels was explored using intergroup comparisons, and confusion matrices were analyzed at various transfusion cutoff values. In the absence of interference, there was a strong correlation between PLT-H and PLT-IRM (r = 0.993, 95% CI: 0.990-0.996). Under various interference conditions, the correlation between PLT-H and PLT-IRM was between 0.963 and 0.992, with an average deviation of -14.56 to -2.02. The performance of PLT-H against interference did not change significantly with increasing levels of small RBCs, large PLTs, and RBC fragments (P = .5704, 0.0832, 0.9893). In low-value samples (PLT <100 × 109/L), the coefficient of variation (CV) for PLT-H was less than 7.6%, regardless of the presence or absence of interfering substances. In addition, there was a high agreement between PLT-H and PLT-IRM (ICC = 0.972). Confusion matrice analysis at each medical decision level showed similarity to methods using the fluorescence channel (PLT-O) and superiority to the impedance channel (PLT-I). Compared with PLT-I, PLT-H has higher accuracy in PLT counting, stronger anti-interference ability, better performance in low-value samples at no extra economic cost and can be more useful for platelet transfusion decision-making. PLT-H is a novel method for platelet counting that offers higher accuracy, providing physicians with the ability to make better medical decisions, particularly in cases where values are low, or interference is present. As it does not require additional reagents, it is highly likely to replace PLT-I and become the mainstream method for platelet counting in the future.

The diagnostic accuracy of Sysmex XN for identification of pseudothrombocytopenia using various thresholds for definition of platelet aggregation

INTRODUCTION

The aim of this study was to investigate the diagnostic accuracy of the flag PLT-Clumps from the WNR/WDF and the PLT-F channels from Sysmex XN and to study how different cut-offs for investigation for pseudothrombocytopenia (PTCP) and the definition of platelet aggregation affected the diagnostic accuracy.

METHODS

A smear review was performed for samples with platelet count <150 × 109 /L and samples flagged for platelet aggregation by Sysmex XN-20. The samples were investigated for platelet aggregation in 30 fields using 40× objective. Findings were classified by size and quantity using two definitions of aggregation: the Norwegian quality improvement of laboratory investigations (Noklus) and the Groupe Francophone de'Hematologie Cellulaire (GFHC). The Q-values for the PLT-Clumps flag from the WNR/WFD channel and the PLT-F channel were compared with smear findings.

RESULTS

ROC analysis showed that the diagnostic accuracy of the PLT-clumps flags increased with increasing stringency of the definition of platelet aggregation and when only samples with thrombocytopenia were investigated. With the most stringent PTCP definitions, the diagnostic accuracy of the PLT-Clumps flag from PLT-F was very high (AUC 0.97-0.98) and markedly better than for WNR/WDF.

CONCLUSION

The diagnostic accuracy of PLT-F from Sysmex XN-20 for identification of PTCP was very good and superior to the WNDR/WDF channel in samples with platelet count <150 × 109 /L and a moderate to high number of aggregates in the smear. There is a need for a more precise definition of platelet aggregation.

Performance evaluation of the new platelet measurement channel on the BC-6800 Plus automated hematology analyzer

OBJECTIVE

To evaluate the performance of new optical platelet measurement channel on the BC-6800 Plus automated blood cell analyzer.

METHODS

The basic PLT count performance of the BC-6800 Plus was evaluated according to the requirements of the Clinical Laboratory and Standards Institute (CLSI) Document H26-A2. In addition, low-PLT-value specimens, red blood cell debris specimens, small red blood cell specimens, and giant PLT specimens were detected with the blood cell analyzer and a flow cytometer. Whole-blood specimens in ethylenediaminetetraacetic acid (EDTA) or sodium citrate anticoagulant tubes from 20 patients with EDTA-dependent PLT aggregation were determined in CDR mode of the analyzer.

RESULTS

Blank counting and the carryover contamination rate of PLTs using the BC-6800 Plus both met the technical requirements. For abnormal PLT specimens, PLT-O 8× and PLT-I both exhibited high comparability with flow cytometry. The comparability of PLT-O 8× with flow cytometry was better than that of PLT-I. In EDTA-anticoagulated blood specimens from 20 patients with EDTA-dependent PLT aggregation, the results of PLT-O were significantly higher than those for PLT-I using samples from the same tubes (P < .001). However, the PLT counts were similar between these two methods for sodium citrate-anticoagulated blood specimens (P = .263).

CONCLUSION

The performance of PLT-O 8× in the BC-6800 Plus met the technical requirements. PLT-O 8× exhibited better reproducibility than did PLT-I for low-PLT-value samples. Reexamination of abnormal PLT specimens using PLT-O 8× yielded more accurate results. PLT-O performed significantly better than PLT-I in the detection of EDTA-dependent PLT-aggregation specimens.

Pseudothrombocytopenia-A Review on Causes, Occurrence and Clinical Implications

Pseudothrombocytopenia (PTCP), a relative common finding in clinical laboratories, can lead to diagnostic errors, overtreatment, and further (even invasive) unnecessary testing. Clinical consequences with potential life-threatening events (e.g., unnecessary platelet transfusion, inappropriate treatment including splenectomy or corticosteroids) are still observed when PTCP is not readily detected. The phenomenon is even more complex when occurring with different anticoagulants. In this review we present a case of multi-anticoagulant PTCP, where we studied different parameters including temperature, amikacin supplementation, measurement methods, and type of anticoagulant. Prevalence, clinical risk factors, pre-analytical and analytical factors, along with clinical implications, will be discussed. The detection of an anticoagulant-dependent PTCP does not necessarily imply the presence of specific disorders. Conversely, the incidence of PTCP seems higher in patients receiving low molecular weight heparin, during hospitalization, or in men aged 50 years or older. New analytical technologies, such as fluorescence or optical platelet counting, will be soon overturning traditional algorithms and represent valuable diagnostic aids. A practical laboratory approach, based on current knowledge of PTCP, is finally proposed for overcoming spuriously low platelet counts.

Pseudo-thrombocytopenia (PTCP). A challenge in the daily laboratory routine?

Anticoagulation with ethylenediaminetetraacetic acid (EDTA) is a necessary pre-requisite for automated blood cell counting. With a prevalence of 0.01–1%, EDTA anticoagulation is accompanied by time- and temperature-dependent in vitro aggregation of platelets, resulting in false low counts. To avoid wrong clinical conclusions, spontaneous anticoagulant-induced platelet agglutination should therefore be recognized during analysis. This might be a challenge for the routine laboratory.

The actual knowledge of this rare but clinically important laboratory artefact will be summarized and reviewed in the following, based on our own experiences and the available literature. This includes pathophysiological and epidemiological aspects, valuable information regarding the detection and prevention of a PTCP, and the possibilities for determination of the correct platelet count.