Platelet Counting: Ugly Traps and Good Advice. Proposals from the French-Speaking Cellular Hematology Group (GFHC)

Evaluation of artificial intelligence-assisted morphological analysis for platelet count estimation

INTRODUCTION

This study aims to assess the performance of the platelet count estimation using artificial intelligence technology on the MC-80 digital morphology analyzer.

METHODS

Digital morphology analyzer uses two different computational principles for platelet count estimation: based on PLT/RBC ratio (PLT-M1) and estimate factor (PLT-M2). 977 samples with various platelet counts (low, median, and high) were collected. Out of these, 271 samples were immunoassayed using CD61 and CD41 antibodies. The platelet counts obtained from the hematology analyzer (PLT-I and PLT-O), digital morphology analyzer (PLT-M1 and PLT-M2), and flow cytometry (PLT-IRM) were compared.

RESULTS

There was no significant deviation observed before and after verification for both PLT-M1 and PLT-M2 across the analysis range (average bias: -0.845/-0.682, 95% limit of agreement (LOA): -28.675-26.985/-29.420-28.056). When platelet alarms appeared, PLT-M1/PLT-M2 showed the strongest correlation with PLT-IRM than PLT-I with PLT-IRM (r: 0.9814/0.9796 > 0.9601). The correlation between PLT-M1/PLT-M2 and PLT-IRM was strong for samples with interference, such as large platelets or RBC fragments, but relatively weak in small RBCs. The deviation between PLT-M1 and PLT-M2 is related to the number of RBCs. Compared with PLT-I, PLT-M1/PLT-M2 showed higher accuracy for platelet transfusion decisions, especially for samples with low-value PLT.

CONCLUSION

The novel platelet count estimation on the MC-80 digital morphology analyzer provides high accuracy, especially the reviewed result, which can effectively confirm suspicious platelet count.

An Introduction to the Complete Blood Count for Clinical Chemists: Platelets

BACKGROUND

The most ordered laboratory test worldwide is the complete blood count (CBC).

CONTENT

In this primer, an introduction to platelet testing in the context of the CBC is provided with a discussion of the laboratory evaluation of platelet abnormalities including thrombocytopenia and thrombocytosis.

SUMMARY

As clinical chemists continue to be tasked to direct laboratories outside of the traditional clinical chemistry sections such as hematology, expertise must be developed. This primer is dedicated to that effort.

ACVIM consensus statement on the diagnosis of immune thrombocytopenia in dogs and cats

Immune thrombocytopenia (ITP) is the most common acquired primary hemostatic disorder in dogs. Immune thrombocytopenia less commonly affects cats but is an important cause of mortality and treatment-associated morbidity in both species. Immune thrombocytopenia remains a diagnosis of exclusion for which diagnostic guidelines are lacking. Primary, or non-associative, ITP refers to autoimmune platelet destruction. Secondary, or associative, ITP arises in response to an underlying disease trigger. However, evidence for which comorbidities serve as ITP triggers has not been systematically evaluated. To identify key diagnostic steps for ITP and important comorbidities associated with secondary ITP, we developed 12 Population Evaluation/Exposure Comparison Outcome (PECO) format questions. These questions were addressed by evidence evaluators utilizing a literature pool of 287 articles identified by the panelists using a structured search strategy. Evidence evaluators, using panel-designed templates and data extraction tools, summarized evidence and created guideline recommendations that then were integrated by diagnosis and comorbidity domain chairs. The revised PECO responses underwent a Delphi survey process to reach consensus on final guidelines. A combination of panel expertise and PECO responses were employed to develop algorithms for diagnosis of ITP in dogs and cats, which also underwent 4 iterations of Delphi review. Comorbidity evidence evaluators employed an integrated measure of evidence (IME) tool to determine evidence quality for each comorbidity; IME values combined with evidence summaries for each comorbidity were integrated to develop ITP screening recommendations, which also were subjected to Delphi review. Commentary was solicited from multiple relevant professional organizations before finalizing the consensus. The final consensus statement provides clinical guidelines for the diagnosis of, and underlying disease screening for, ITP in dogs and cats. The systematic consensus process identified numerous knowledge gaps that should guide future studies. This statement is a companion manuscript to the ACVIM Consensus Statement on the Treatment of Immune Thrombocytopenia.

The effect of oscillation depolymerization on ethylenediaminetetraacetic acid-dependent platelet aggregation samples: A cross-over study

INTRODUCTION

Ethylenediaminetetraacetic acid (EDTA)-dependent platelet aggregation (PA) can cause medical errors. Currently, there is no reliable method for completely solving this problem. This study aims to solve this problem that has plagued clinical practice for many years by using oscillation method.

METHODS

Sixty-one EDTA-PA samples were collected, divided, and disaggregated using the oscillation method at various times and speeds. The samples were analyzed using routine blood tests and blood smears.

RESULTS

Platelet counts (PLT) were increased significantly after oscillation. PLT in the 3000 rpm for 0.5 min group was significantly higher than that in the 500 rpm for 0.5 min group (p < 0. 01). After 3000 rpm oscillation, the PLT gradually increased with time, while compared with the 10-min group, the PLT in the 13-min group showed no significant differences. The effective disaggregation rates in the EDTA-PA samples using the oscillation method and sodium citrate anticoagulant were 96.72% and 65.57%, respectively. There were no significant changes in white blood cell (WBC) or red blood cell (RBC) counts or morphology after the use of the oscillation method.

CONCLUSION

The oscillation method effectively depolymerized EDTA-PA without adverse effects on WBC and RBC. The implementation of this technique promises to resolve the issue of EDTA-PA.

Evaluation of a diagnostic platelet aggregation test strategy for platelet rich plasma samples with low platelet counts

INTRODUCTION

Light transmission aggregometry (LTA) is important for diagnosing platelet function disorders (PFD) and von Willebrand disease (VWD) affecting ristocetin-induced platelet aggregation (RIPA). Nonetheless, data is lacking on the utility of LTA for investigating thrombocytopenic patients and platelet rich plasma samples with low platelet counts (L-PRP). Previously, we developed a strategy for diagnostic LTA assessment of L-PRP that included: (1) acceptance of referrals/samples, regardless of thrombocytopenia severity, (2) tailored agonist selection, based on which are informative for L-PRP with mildly or severely low platelet counts, and (3) interpretation of maximal aggregation (MA) using regression-derived 95% confidence intervals, determined for diluted control L-PRP (C-L-PRP).

METHODS

To further evaluate the L-PRP LTA strategy, we evaluated findings for a subsequent patient cohort.

RESULTS

Between 2008 and 2021, the L-PRP strategy was applied to 211 samples (11.7% of all LTA samples) from 192 unique patients, whose platelet counts (median [range] × 109 /L) for blood and L-PRP were: 105 [13-282; 89% with thrombocytopenia] and 164 [17-249], respectively. Patient-L-PRP had more abnormal MA findings than simultaneously tested C-L-PRP (p-values <0.001). Among patients with accessible electronic medical records (n = 181), L-PRP LTA uncovered significant aggregation abnormalities in 45 (24.9%), including 18/30 (60%) with <80 × 109  platelets/L L-PRP, and ruled out PFD, and VWD affecting RIPA, in others. The L-PRP LTA strategy helped diagnose VWD affecting RIPA, Bernard Soulier syndrome, familial platelet disorder with myeloid malignancy, suspected ITGA2B/ITGB3-related thrombocytopenia, and acquired PFD.

CONCLUSION

Diagnostic LTA with L-PRP, using a strategy that considers thrombocytopenia severity, is feasible and informative.

Performance evaluation of a novel platelet count parameter, hybrid platelet count, on the BC-780 automated hematology analyzer

OBJECTIVES

Automated hematology analysis is expected to improve the performance of platelet counting. We evaluated the performance of a new platelet counting, hybrid (PLT-H) and also impedance (PLT-I) and optical (PLT-O) on the BC-780 automated hematology analyzer compared to the international reference method (IRM) in blood samples with thrombocytopenic and platelet interference.

METHODS

The basic platelet count performance of the BC-780 automated hematology analyzer was evaluated according to the requirements of the Clinical Laboratory and Standards Institute (CLSI) Document H26-A2. Additionally, the thrombocytopenic (low PLT count) blood samples and the platelet interference blood samples including fragmented red blood cells (RBCs), microcytes or small RBCs, and giant platelets were determined with the BC-780 hematology analyzer compared to the IRM.

RESULTS

Blank counting and the carry-over contamination rate of platelet count using the BC-780 both met the manufacturers' claim. For both 123 thrombocytopenic and 232 platelet interference blood samples (72 fragmented RBCs, 91 microcytes and 51 giant platelets), all three platelet counting methods exhibited high comparability with the IRM (the lowest correlation (r)=0.916). Interestingly, the comparability of PLT-H (r=0.928-0.986) with the IRM was better than that of PLT-I (r=0.916-0.979).

CONCLUSIONS

The performance of PLT-H in the BC-780 met the manufacturer's specifications. PLT-H exhibits better reproducibility than did PLT-I, correlates well with the PLT-O for thrombocytopenic samples and demonstrates good anti-interference ability. PLT-H counting is therefore recommended as a zero-cost alternative platelet counting method for platelet interference samples in clinical settings.

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.

Stability over time of immature platelet fraction and comparison between EDTA and citrated whole blood samples

BACKGROUND

Immature platelets (IP) are the youngest circulating platelets, released from megakaryocytes, and demonstrating increased dimensions, significant RNA content, and enhanced activity. Immature platelet research focuses on a differential diagnostic help in patients with thrombocytopenia. The objectives of this study were to compare the variability of IP in citrate and EDTA samples, and to determine stability over time.

METHODS

Fifty-six patients were included for comparison between EDTA and citrate whole blood sample collection. Among the patients, 28 had thrombocytopenia (platelet count < 150G/L). Platelet measurement impedancemetry and fluorimetry were performed with Sysmex XN-9000. The immature platelet fraction (IPF) and absolute immature platelet count (A-IPC) were determined with a fluorescent method.

RESULTS

The mean value of platelet count with fluorescence was, in EDTA sample, 215 ± 171 and, in citrate sample, 153 ± 118 G/L. No significant difference was observed between IPF between EDTA and citrate (7.74 ± 6.68% vs. 8.45 ± 7.37%, p = 0.69), respectively. With the Bland-Altman analysis, the mean difference in the EDTA sample, between 1 and 24 h, was 8.06 ± 6.96% and 8.73 ± 7.12% for IPF, whereas in the citrate sample, between 1 and 6 h, it was 8.60 ± 7.29% and 7.54 ± 6.97%, for IPF. Comparing 1 h EDTA sample with 6 h citrate sample, the variance ratio was 0.974 (95% CI: 0.864-1.084) in IPF.

CONCLUSIONS

We confirmed the potential to conduct IP measurements up to 24 h in the EDTA sample and IPF measurements in the citrate sample for up to 6 h. These results may be useful for the use of IPF, which is a promising parameter whose interest in clinical practice and standardization is not yet well defined.

Pseudothrombocytopenia, beyond a laboratory phenomenon: study of 192 cases

The platelet antibodies that cause pseudothrombocytopenia (PTCP) act only in vitro and do not produce clinical bleeding. Most studies on PTCP have focused on improving differential diagnosis with true thrombocytopenia but studies on the characteristics of patients with PTCP are limited. In this study, we aimed to evaluate the clinical and biological characteristics of 192 patients with PTCP. In addition to general variables, we evaluated automated and microscopic platelet counts, platelet clumps, platelet diameters, immature platelet fraction (IPF), and platelet antibodies. Adult women accounted for the largest subgroup of patients (n=82; 42.7%) and 67 patients (34.9%) were grouped into families. Forty-four patients (22.9%) had one or more associated autoimmune disorders (ADs); 39 relatives of these patients (19.8%) had ADs and 45 relatives (23.4%) had immune thrombocytopenia (ITP) or unspecified thrombocytopenia. Platelet cryptantibodies and/or autoantibodies were positive in 56 patients (30.1%). Most patients (n=169; 80%) had automated platelet counts >80×10⁹/L. In all patients, microscopic platelet counts were ≥150×10⁹/L. The platelet clump index (% increase in microscopic platelet count compared to automatic count) ranged from 30 to >7000%. Platelet diameters and IPF parameters were significantly greater in the PTCP versus healthy controls (p<0.001). A total of 17 patients (8.8%) had had previous ITP or the PTCP evolved into ITP. Our data suggest that PTCP should be considered a situation of autoimmunity; the assessment of platelet clumps has a high diagnostic value; the close association between ITP and PTCP suggests that these conditions could be different phases of the same process.

Comparison of platelet count results on the Sysmex XN between citrate or MgSO4 and K2 EDTA anticoagulants

INTRODUCTION

The aim of this study performed on Sysmex XN is to compare platelet values on citrate and MgSO₄ (TBX) in patients with K2EDTA-induced platelet clusters and to identify platelet biases of these matrices compared to K2EDTA.

METHODS

Sixty patients with K2EDTA-induced platelet clusters were re-sampled with K2EDTA, citrate and TBX. Platelet results were then compared, and smears were analysed for clumping. Platelet results from 120 patients without K2EDTA-induced platelet clusters were compared between K2 EDTA, citrate, and MgSO₄ with impedance and fluorescence modes. Biases from regressions were analysed.

RESULTS

Out of the 60 patients with K2EDTA-induced platelet clusters, none showed platelet clusters with MgSO₄ whereas 50% still showed clusters with citrate. Among those without platelet clusters on citrate, the mean relative difference between (citrate- MgSO₄ )/MgSO₄ was -12.7% in impedance and -9.8% in fluorescence. Among the 120 patients without K2EDTA-induced platelet clusters, in fluorescence the mean relative bias with respect to K2EDTA was -2.06% for MgSO₄ and -10.3% for Citrate. For the MgSO₄ versus K2 EDTA regressions, the maximum absolute values of the 95% CI of the relative biases at 150 × 10⁹ /L (5.45%) and 450 × 10⁹ /L (3.56%) were below the desirable analytical objectives of the EFLM.

CONCLUSION

In patients with K2EDTA-induced platelet clusters, MgSO₄ is preferable to citrate. MgSO₄ provides a bias with XN in fluorescence when compared to EDTA which is within analytical tolerance.

Application of the Fluorescence Method on Sysmex XN9000 Hematology Analyzer for Correcting Platelet Count in Individuals with Microcytosis

OBJECTIVE

Although small red blood cells are a well-known analytical pitfall that could cause artifactual increase of the platelet count, limited information is available on the accuracy of impedance platelet counting in cases with microcytosis. The aim of this study is to assess the accuracy of impedance platelet counting in the presence of small red blood cells, and to establish the optimal mean corpuscular volume (MCV) cutoff to endorse fluorescence platelet counting.

METHODS

In this study, platelet counts estimated by the impedance method on the Sysmex XN9000 analyzer (Sysmex, Kobe, Japan) were compared with those provided by the fluorescence method. The accuracy of impedance platelet counting was assessed. Receiver operating characteristic curve was used to evaluate the performance of MCV in predicting falsely increased platelet counts.

RESULTS

There was a tendency for the impedance method to overestimate the platelet count in samples with 70 fL < MCV ≤ 80 fL, 60 fL < MCV ≤ 70 fL, MCV ≤ 60 fL. Receiver operating characteristic curve analysis showed that a 73.5fL cutoff of MCV was highly sensitive in predicting falsely increased platelet counts.

CONCLUSION

In cases with MCV < 73.5 fL, we strongly suggest that the platelet counts obtained by the impedance method on the Sysmex XN9000 analyzer should be checked and corrected by fluorescence counting.

Platelet count in impedance-based hematology analyzer: Beware of trap!

Among the blood counts, platelet count is most often reported with inconsistency. Many of the analyzers work on electrical impedance principle for red blood cell (RBC) and platelet counting. However, with this technology, factors such as fragmented RBCs, microcytes, cytoplasmic fragments of leukemic cells, lipid particles, fungal yeast forms, and bacteria are known to interfere with platelet count and give spuriously elevated platelet counts. A 72-year-old male was admitted for the treatment of dengue infection who had serial platelet count monitoring. He had an initial platelet count of 48,000/cumm which suddenly improved to 2.6 lakhs within 6 h without any platelet transfusion. Peripheral smear however did not correlate with the machine-derived count. Repeat test after 6 h yielded a result of 56,000/cumm which correlated well with the peripheral smear. This falsely elevated count was due to the presence of lipid particles as the sample was drawn in the postprandial state.

Avoiding Spurious Low Platelet Counts by Redrawing Specimens with First Time Low Platelet Counts

INTRODUCTION

We reviewed our policy of redrawing our pediatric patients with first time platelet counts <100 K/ml to assess the frequency of correction.

MATERIALS AND METHODS

In a Children's Hospital 25-month review of patients that underwent automatic redraws due to low first time platelet counts, we determined the frequency of corrected counts and the sites where these original low platelet counts originated. Only the repeat draw results were reported.

RESULTS

Of 99 children with redrawn specimens, 62% of platelet counts corrected. The most frequent corrections occurred in specimens from the emergency department (74%), pediatric intensive care (71%), and operating room (67%), the fewest from the cardiac intensive care (38%) and general hospital floors (44%).

CONCLUSIONS

The policy of redrawing patients with first time platelet counts <100 K resulted in correction in 62%, and avoided delays and additional charges for repeat testing ordered by the provider.

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.

Platelets as a Gauge of Liver Disease Kinetics?

A multitude of laboratory and clinical interferences influence the utility of platelet-based diagnostic indices, including immature platelet fraction, in longitudinal monitoring and prognostication of patients with chronic liver disease (CLD). The complex yet highly regulated molecular basis of platelet production and clearance kinetics becomes dysregulated in liver pathogenesis. These underlying molecular mechanisms, including premature platelet clearance and bone marrow suppression in parallel with the progressive (e.g., treatment-naïve) or regressive (e.g., on-treatment and off-treatment) disease courses, involved in CLDs, may further confound the changes in platelet–liver correlations over time. Platelet count and function are commonly and secondarily altered in vivo in CLDs. However, the precise characterization of platelet functions during cirrhosis, including in vitro platelet aggregation, has proven challenging due to interferences such as thrombocytopenia. A flow cytometric approach may help monitor the unstably rebalanced hyper- and hypoaggregable states in patients with cirrhosis at risk of hyperaggregable, prothrombotic, or bleeding events. Studies have attempted to stratify patients with cirrhosis by substages and prognosis through the use of novel indices such as the ratio of in vitro endogenous platelet aggregation to platelet count. This review attempts to highlight clinical and laboratory precautions in the context of platelet-assisted CLD monitoring.

Unreliable Automated Complete Blood Count Results: Causes, Recognition, and Resolution

Automated hematology analyzers generate accurate complete blood counts (CBC) results on nearly all specimens. However, every laboratory encounters, at times, some specimens that yield no or inaccurate result(s) for one or more CBC parameters even when the analyzer is functioning properly and the manufacturer’s instructions are followed to the letter. Inaccurate results, which may adversely affect patient care, are clinically unreliable and require the attention of laboratory professionals. Laboratory professionals must recognize unreliable results, determine the possible cause(s), and be acquainted with the ways to obtain reliable results on such specimens. We present a concise overview of the known causes of unreliable automated CBC results, ways to recognize them, and means commonly utilized to obtain reliable results. Some examples of unreliable automated CBC results are also illustrated. Pertinent analyzer-specific information can be found in the manufacturers’ operating manuals.

Automated Detection of Dysplasia: Data Mining from Our Hematology Analyzers

Myelodysplastic syndromes (MDSs) are clonal hematopoietic diseases of the elderly, characterized by chronic cytopenia, ineffective and dysplastic hematopoiesis, recurrent genetic abnormalities and increased risk of progression to acute myeloid leukemia. Diagnosis on a complete blood count (CBC) can be challenging due to numerous other non-neoplastic causes of cytopenias. New generations of hematology analyzers provide cell population data (CPD) that can be exploited to reliably detect MDSs from a routine CBC. In this review, we first describe the different technologies used to obtain CPD. We then give an overview of the currently available data regarding the performance of CPD for each lineage in the diagnostic workup of MDSs. Adequate exploitation of CPD can yield very strong diagnostic performances allowing for faster diagnosis and reduction of time-consuming slide reviews in the hematology laboratory.

Resolution of platelet count interference due to cytoplasmic fragments of leukaemic cells by flow cytometry in acute myeloid leukaemia

BACKGROUND

Platelet count interference could lead to problems in clinical decisions especially in the cases of thrombocytopenia. Here we report a case of platelet count interference in Beckman Coulter DxH800 haematology analyser due to cytoplasmic fragments of leukaemic cells in acute myeloid leukaemia. A 19-year-old female patient presented to the emergency department with bruises and anaemic symptoms. A machine platelet count (by impedance method) was 40 × 10⁹ /L. There was a flag on platelet count interference by debris. Peripheral blood smear showed some bluish cytoplasmic fragments are seen mimicking platelets.

METHOD

Immunological platelet counting by flow cytometry using fluorochrome-labeled antibodies against platelet markers CD41 and CD61 was attempted by adopting and modifying from the ICSH reference method for platelet counting. Events with low forward scatter and positive CD41 and/or CD61 expression were identified as platelets, and events with high forward scatter and negative CD41 and CD61 expression were identified as red cells.

RESULTS

The platelet count was derived from the formula: Platelet count = RBC count (Haematology analyser) × PLT event (flow cytometry)/RBC events (flow cytometry). The immunological platelet count was determined to be 2 × 10⁹ /L, which is much lower than the original machine count and platelet transfusion was warranted.

The flagging features of the Sysmex XN-10 analyser for detecting platelet clumps and the impacts of platelet clumps on complete blood count parameters

OBJECTIVES

Platelet clumps present in anticoagulant specimens may generate a falsely decreased platelet count and lead to an incorrect diagnosis. A clear understanding of the ability of a haematology analyser (HA) to detect platelet clumps is important for routine work in the clinical laboratory.

METHODS

Citrate-anticoagulated whole-blood samples were collected from various patients as a negative group. Adenosine diphosphate (ADP)-induced platelet aggregation was performed on those negative samples to mimic platelet-clump-containing (positive) samples. The 'platelet clumps' and 'platelet abnormal' flags generated by the Sysmex XN-10 instrument were used to assess the flagging performance of this HA and demonstrate its flagging features. The complete blood count (CBC) results of paired negative and positive samples were compared to evaluate the impact of platelet clumps on the CBC parameters.

RESULTS

A total of 187 samples were eligible for this study. The total accuracy, sensitivity, and specificity of the platelet clumps flag were 0.786, 0.626, and 0.947, respectively. The total accuracy, sensitivity, and specificity of the platelet abnormal flag were 0.631, 0.348, and 0.914, respectively. A separate assessment focusing on the positive samples with low platelet counts showed that the total sensitivities of the platelet clumps and platelet abnormal flags were 0.801 and 1.000, respectively. Platelet clumps may interfere with the leukocyte count and with platelet and erythrocyte indices.

CONCLUSIONS

Platelet clumps can influence not only platelet indices but also leukocyte and erythrocyte counts. The Sysmex XN-10 instrument is sensitive to positive samples with low platelet counts but insensitive to those with high platelet counts.

Feasibility of a mean platelet volume standard: an international council for standardization in hematology (ICSH) inter-laboratory study

We have evaluated a commercial-fixed porcine platelet preparation (with and without added fixed human red blood cells (RBC)) for the potential standardization of mean platelet volume (MPV) measurements. The standards (Biotechne) were distributed internationally to 19 laboratories including all major hematology instrument manufacturers and academic/pathology laboratories. Overall, the standards demonstrated excellent stability up to 1 month within both MPV values and platelet counts when stored at 4°C. The presence of RBC significantly increased the platelet count and MPV values compared to platelets alone. However, as expected, there were differences in MPV values between different instruments and manufacturers. MPV values were also significantly higher in the whole blood standard compared to the platelet standard in the majority of instruments except with some instruments, where MPV values were significantly higher in the platelet only preparation. To further investigate this phenomenon, two different Platelet MPV preparations (with low and high MPV) in combination with 3 different RBC MCV preparations (with low, normal or high MCVs) were tested to try and further elucidate how RBC populations may impact upon platelet analysis (count, MPV, and PDW) using a single impedance analyzer. Both MPV and MCV values showed good stability over the course of the study for up to 50 days. As expected, the RBC preparation with the lowest MCV had the greatest impact on the MPV. However, this was not observed with an increase in MCV of the RBC or by a larger MPV of the platelet population. To further understand how different gating strategies may also influence results, we investigated the effect of either fixed or floating gate strategies upon MPV raw data from patient samples in a single impedance analyzer. Overall, it was clear that floating and fixed gate strategies also significantly impact upon MPV values. In conclusion, we have demonstrated the potential of an MPV standard with good stability characteristics for calibrating and comparing full blood counters that use different analysis principles, gating and MPV calculations. This may facilitate future instrument calibration and harmonization of results between different technologies.

Screening and diagnosis of inherited platelet disorders

Inherited platelet disorders are important conditions that often manifest with bleeding. These disorders have heterogeneous underlying pathologies. Some are syndromic disorders with non-blood phenotypic features, and others are associated with an increased predisposition to developing myelodysplasia and leukemia. Platelet disorders can present with thrombocytopenia, defects in platelet function, or both. As the underlying pathogenesis of inherited thrombocytopenias and platelet function disorders are quite diverse, their evaluation requires a thorough clinical assessment and specialized diagnostic tests, that often challenge diagnostic laboratories. At present, many of the commonly encountered, non-syndromic platelet disorders do not have a defined molecular cause. Nonetheless, significant progress has been made over the past few decades to improve the diagnostic evaluation of inherited platelet disorders, from the assessment of the bleeding history to improved standardization of light transmission aggregometry, which remains a "gold standard" test of platelet function. Some platelet disorder test findings are highly predictive of a bleeding disorder and some show association to symptoms of prolonged bleeding, surgical bleeding, and wound healing problems. Multiple assays can be required to diagnose common and rare platelet disorders, each requiring control of preanalytical, analytical, and post-analytical variables. The laboratory investigations of platelet disorders include evaluations of platelet counts, size, and morphology by light microscopy; assessments for aggregation defects; tests for dense granule deficiency; analyses of granule constituents and their release; platelet protein analysis by immunofluorescent staining or flow cytometry; tests of platelet procoagulant function; evaluations of platelet ultrastructure; high-throughput sequencing and other molecular diagnostic tests. The focus of this article is to review current methods for the diagnostic assessment of platelet function, with a focus on contemporary, best diagnostic laboratory practices, and relationships between clinical and laboratory findings.

Performance of Platelet Counting in Thrombocytopenic Samples: Comparison between Mindray BC-6800Plus and Sysmex XN-9000

The performance of platelet (PLT) counting in thrombocytopenic samples is crucial for transfusion decisions. We compared PLT counting and its reproducibility between Mindray BC-6800Plus (BC-6800P, Mindray, Shenzhen, China) and Sysmex XN-9000 (XN, Sysmex, Kobe, Japan), especially focused on thrombocytopenic samples. We analyzed the correlation and agreement of PLT-I channels in both analyzers and BC-6800P PLT-O mode and XN PLT-F channel in 516 samples regarding PLT counts. Ten thrombocytopenic samples (≤2.0 × 10⁹/L by XN PLT-F) were measured 10 times to investigate the reproducibility with the desirable precision criterion, 7.6%. The correlation of BC-6800P PLT-I and XN PLT-I was arranged moderate to very high; but the correlation of BC-6800P PLT-O and XN PLT-F was arranged high to very high. Both BC-6800P PLT-I vs. XN PLT-I and BC-6800P PLT-O vs. XN PLT-F showed very good agreement (κ = 0.93 and κ = 0.94). In 41 discordant samples between BC-6800P PLT-O and XN PLT-F at transfusion thresholds, BC-6800P PLT-O showed higher PLT counts than XN-PLT-F, except the one case. BC-6800P PLT-O exceeded the precision criterion in one of 10 samples; but XN PLT-F exceeded it in six of 10 samples. BC-6800P would be a reliable option for PLT counting in thrombocytopenic samples with good reproducibility.

Kanamycin Supplement for the Disaggregation of Platelet Clumps in EDTA-Dependent Pseudothrombocytopenia Specimens

OBJECTIVE

To indicate the ability to disaggregate platelet clumps by vortex mixing and kanamycin supplementation in EDTA-dependent pseudothrombocytopenia (EDTA-PTCP) specimens.

MATERIALS AND METHODS

For patients with EDTA-PTCP, citrate-anticoagulated, primary EDTA-anticoagulated, vortex-mixed, and kanamycin-treated specimens were tested for complete blood count and platelet-related parameters.

RESULTS

Forty-eight specimens were included. Nineteen (39.6%) of the vortex-mixed specimens and 42 (87.5%) of the kanamycin-treated specimens revealed platelet counts more than those of the primary EDTA specimens, with levels exceeding 100 × 109/L. The platelet count and platelet recovery of the kanamycin-treated specimens were higher than those of the vortex-mixed specimens.

CONCLUSION

Kanamycin supplementation to EDTA-PTCP blood may be considered as an alternative approach when the recollection of specimens is impractical. Only platelet-related parameters from kanamycin treatment were suitable for guiding patient management. Further studies about the impact of these methods in patients with various conditions, such as in patients with advanced kidney disease, should be conducted.

2021 update of the 2012 ICSH Recommendations for identification, diagnostic value, and quantitation of schistocytes: Impact and revisions

In 2012, the International Council for Standardization in Hematology (ICSH) published recommendations for the identification, quantitation, and diagnostic value of schistocytes. In the present review, the impact of these recommendations is evaluated. This work is based on citations in peer-reviewed papers published since 2012. The first 2012 ICSH Recommendations have also been revised to incorporate newly published data in the literature and current best laboratory practice. Recommended reference ranges have been proposed for healthy adults and full-term neonates of 1% or less schistocytes. More than 1% of morphologically identified schistocytes on the blood film are considered suspicious for thrombotic microangiopathy. For preterm infants, a normal level of 5% or less is recommended. The fragment red cell count (FRC) generated by some automated hematological analyzers provides a valuable screening tool for the presence of schistocytes. Specifically, the absence of FRCs can be used as a valuable parameter to exclude the presence of schistocytes on the blood film. The validity and usefulness of microscope schistocytes and automated FRCs, respectively, are discussed in the context of the laboratory diagnostic tests used for thrombotic microangiopathies.

EDTA-dependent pseudothrombocytopenia in patients with hepatosplenic schistosomiasis mansoni: a clinical management alert

BACKGROUND

Hepatosplenic schistosomiasis mansoni (HS) is associated with thrombocytopenia. Accurate platelet counts are required for identification and management of HS patients. EDTA-dependent pseudothrombocytopenia (EDTA-PTCP) is an in vitro phenomenon of anticoagulant-activated platelet agglutination resulting in low platelet counts by automated methods. The prevalence of EDTA-PCTP in schistosomiasis is unknown and only one case has been described. Our aims were to determine the prevalence of EDTA-PTCP in HS and evaluate alternative methods to overcome this analytical error.

METHODS

Blood samples from 56 HS patients and 56 healthy volunteers were collected, and platelet counts were obtained using standard microscopy and automated (electric impedance) methods. Automated platelet counts and the presence of platelet clumps in blood smears were evaluated in samples collected in EDTA or sodium citrate tubes 20 and 180 min after blood collection.

RESULTS

EDTA-PTCP was more frequent in HS patients than healthy volunteers (8.92% vs 0.00%, p<0.0285). Platelet clumps and PTCP were also observed in samples collected in sodium citrate tubes, refuting its use as an alternative method.

CONCLUSIONS

Automated platelet counts in blood samples from HS patients should be performed right after blood collection in EDTA tubes and verified by manual counts in blood smears.

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.

Reference Intervals for Platelet Counts in the Elderly: Results from the Prospective SENIORLAB Study

Currently, age- and sex-independent reference limits (RLs) are frequently used to interpret platelet counts in seniors. We aimed to define and validate reference intervals (RIs) for platelet counts within the framework of the prospective SENIORLAB study. Subjectively healthy Swiss individuals aged 60 years and older were prospectively included and followed for morbidity and mortality. Participants who had circumstances known to affect platelet counts were excluded. The obtained RIs were validated with indirect statistical methods. Frequencies of abnormal platelet counts in a population-based setting, including 41.5% of the entire age-specific population of the Principality of Liechtenstein, were compared by using age- and sex-independent RIs and the RLs obtained in the present study. For males (n = 542), 95% RIs for platelet counts were defined as follows: 150–300 × 10⁹/L (60–69 years); 130–300 × 10⁹/L (70–79 years); and 120–300 × 10⁹/L (80 years and above). For females (n = 661), the consolidated age-independent 95% RI was 165–355 × 10⁹/L. These RI values were validated by indirect RI determination of 51,687 (30,392 female/21,295 male) patients of the same age. Age- and sex-independent RIs exhibited imbalanced frequencies of abnormal platelet counts between the two sexes, which were corrected by introducing age- and sex-specific RLs. In conclusion, females have higher platelet counts than males. Whereas the upper RL for males remains constant, the lower RL decreases with age. We propose to abandon the practice of employing sex- and age-independent RL for platelet counts in the elderly.

Effects of Time-Interval since Blood Draw and of Anticoagulation on Platelet Testing (Count, Indices and Impedance Aggregometry): A Systematic Study with Blood from Healthy Volunteers

Platelet count, indices (mean volume, young-immature platelet fraction) and aggregation are widely used laboratory parameters to investigate primary hemostasis. We performed a systematic, thorough evaluation of the influence of the time-interval since blood draw from 20 healthy individuals and of the anticoagulation of collected blood on such parameters. Blood was anticoagulated with citrate, K₂-ethylenediaminetetraacetic acid (EDTA) and hirudin and analyzed 5, 30, 60, 120 and 180 min after blood draw. Multiple electrode aggregometry (MEA) was performed with either hirudin (half-diluted with NaCl) or citrate samples (half-diluted with NaCl or CaCl₂ 3 mM). Platelet count and indices (Sysmex XN-20) were rather stable over time with EDTA blood. MEA results were lower with citrate blood than with hirudin blood; supplementation with calcium was partially compensatory. MEA results were also lower when performed less than 30 or more than 120 min after blood draw. Platelet clumping, quantitatively estimated with microscope examination of blood smears, was more important in hirudin blood than citrate or EDTA blood and could explain some of the differences observed between preanalytical variables. The results stress once more the importance of preanalytical variables in hemostasis laboratory testing. Decision thresholds based on those tests are only applicable within specific preanalytical conditions.