Standardizing leucocyte PNH clone detection: an international study

[Expression and influencing factors of hepcidin in classical paroxysmal nocturnal hemoglobinuria]

目的

研究铁调素在经典型阵发性睡眠性血红蛋白尿症（PNH）患者血清中的表达及其影响因素。

方法

以2016年3月至2017年3月36例经典型PNH患者为研究对象，采用ELISA方法检测血清铁调素水平，并结合患者铁稳态状况和临床资料，分析经典型PNH患者血清铁调素水平与血清铁蛋白（SF）、可溶性转铁蛋白受体、C反应蛋白、EPO、网织红细胞绝对值、网织红细胞血红蛋白等血液学参数的相关性。

结果

36例经典型PNH患者血清铁调素水平为32.03（23.11，118.48）µg/L，明显低于正常对照组的181.42（106.80，250.53）µg/L（z=−5.107，P<0.001）。其中，铁蛋白正常经典型PNH患者血清铁调素水平为56.41（44.60，95.06）µg/L，经典型PNH伴缺铁组血清铁调素水平为23.75（21.77，30.35）µg/L，均低于正常对照组；而经典型PNH伴铁蛋白升高组血清铁调素水平为336.19（304.19，375.08）µg/L，高于正常对照组、铁蛋白正常经典型PNH组及经典型PNH伴缺铁组。多重线性回归分析显示SF、转铁蛋白饱和度和血清白蛋白水平是经典型PNH患者血清铁调素水平的独立影响因素。

结论

经典型PNH患者血清铁调素水平减低，其表达主要受铁代谢因素影响。

Multicenter validation of a simplified method for paroxysmal nocturnal hemoglobinuria screening

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) diagnostic guidelines recommend single-tube five- to six-color or two-tube four-color assays. PNH clones are detectable in only a fraction of patients at risk, and screening for new PNH cases can be complex and expensive. In this multicenter study, we have validated a simplified, one-tube two-color FLAER-based assay suitable for PNH screening.

METHODS

Six laboratories received samples containing spiked PNH leukocyte clones to be analyzed in parallel with a common six-color cocktail (FLAER/CD24/CD45/CD64/CD15/CD14) and a simplified two-color mixture (FLAER/CD15), a shared calibration procedure, and a common analysis protocol. Replicate precision and sensitivity tests were performed on PNH patients, from undiluted to 1:10 000. Specificity tests were performed on normal donors to identify the possible sources of artifacts.

RESULTS

The performance comparison between six-color and two-color assays showed an excellent agreement for granulocyte PNH clones. Dilution experiments showed an accurate detectability down to 0.01% sensitivity level for granulocyte PNH clones and to 1% for monocytes. Specificity experiments disclosed that basophils and platelets can contaminate the monocyte gate and generate false PNH events.

CONCLUSIONS

A simplified two-color (FLAER/CD15) PNH screening test has been validated in a highly standardized multicenter study and proved feasible and effective in ongoing regional programs. Precision, sensitivity, and specificity of the simplified test for granulocytes were comparable to the more complex and expensive six-color assay and applicable for screening also in peripheral laboratories. The diagnostic confirmation of PNH should be always performed by a reference center using the established technique on all cell lineages.

Technical advances in flow cytometry-based diagnosis and monitoring of paroxysmal nocturnal hemoglobinuria

Objective:

To discuss the implementation of technical advances in laboratory diagnosis and monitoring of paroxysmal nocturnal hemoglobinuria for validation of high-sensitivity flow cytometry protocols.

Methods:

A retrospective study based on analysis of laboratory data from 745 patient samples submitted to flow cytometry for diagnosis and/or monitoring of paroxysmal nocturnal hemoglobinuria.

Results:

Implementation of technical advances reduced test costs and improved flow cytometry resolution for paroxysmal nocturnal hemoglobinuria clone detection.

Conclusion:

High-sensitivity flow cytometry allowed more sensitive determination of paroxysmal nocturnal hemoglobinuria clone type and size, particularly in samples with small clones.

Objetivo:

Discutir as melhorias técnicas no diagnóstico e no acompanhamento laboratorial de hemoglobinúria paroxística noturna para a validação da técnica de citometria de fluxo de alta sensibilidade.

Métodos:

Estudo retrospectivo, que envolveu a análise de dados laboratoriais de 745 pacientes com hipótese diagnóstica e/ou acompanhamento de hemoglobinúria paroxística noturna por citometria de fluxo.

Resultados:

Os avanços técnicos não só reduziram o custo do ensaio, mas também melhoraram a identificação e a resolução da citometria de fluxo para a detecção de clone hemoglobinúria paroxística noturna.

Conclusão:

A citometria de fluxo de alta sensibilidade possibilitou a identificação do tipo e do tamanho de clone de hemoglobinúria paroxística noturna, especialmente em amostras com pequeno clone.

Current international flow cytometric practices for the detection and monitoring of paroxysmal nocturnal haemoglobinuria clones: A UK NEQAS survey

BACKGROUND

Paroxysmal nocturnal haemoglobinuria (PNH) is a rare acquired genetic disorder, with an incidence of approximately 1.3 new cases per million population per year. Evidence from the UK National External Quality Assessment Service for Leucocyte Immunophenotyping (UK NEQAS LI) programme suggested major discrepancies on how PNH testing is undertaken. To investigate this we surveyed laboratories in the UK NEQAS LI PNH programme and report here the findings.

METHODS

A questionnaire was distributed to all centres registered in UK NEQAS LI flow cytometry programmes (n = 1587). Comprising several subsections, it covered the majority of clinical flow cytometric practices. Participants completed a general section and then the subsections relevant to their laboratory repertoire. One subsection contained 34 questions regarding practices in PNH clone detection.

RESULTS

A total of 105 laboratories returned results for the PNH section; the results demonstrated lack of consensus in all areas of PNH testing. Variation was seen in gating and testing strategies, sensitivity levels and final reporting of test results. Several incorrect practices were highlighted such as inappropriate antibody selection and failure to wash the red blood cells (RBCs) prior to analysis.

CONCLUSION

Despite the availability of consensus guidelines there appears to be no agreement in the detection and monitoring of PNH. We found only fourteen centres using methods compatible with the International Clinical Cytometry Society guidelines. Of specific note we found that no two laboratories used the same method. This technical variation could lead to incorrect diagnoses, highlighting the need for better adoption and understanding of consensus practices. © 2016 International Clinical Cytometry Society.

Evaluation of paroxysmal nocturnal hemoglobinuria screening by flow cytometry through multicentric interlaboratory comparison in four countries

OBJECTIVES

Paroxysmal nocturnal hemoglobinuria (PNH) is currently diagnosed by flow cytometry; although highly sensitive, its interpretation and reporting appear as critical as its technique. Thus, we developed a quality control scheme for the French-speaking region based on the international recommendations for PNH screening.

METHODS

After a topical workshop, we proposed a 1-year, two-step survey program to any volunteering French-speaking clinical laboratory. The first survey consisted of sending raw data files to evaluate gating and the interpretation strategy of each center. The second stipulated sending fresh whole-blood samples to evaluate the whole process and its practice.

RESULTS

Forty-nine participants from voluntary centers returned results for each of the two successive surveys. On virtual survey, 27% reported false-positive PNH created by immature granulocytes, whereas the minor PNH clone was not detected by 9%. On fresh survey, 63% of centers used at least the same six-color combination (CD24, CD14, CD33, CD15, CD45, and fluorescent aerolysin), and nearly 70% of participants were able to perform a sensitivity test less than 0.1% on neutrophils. All participants detected the major PNH clone, yet 16% returned false-positive results for the non-PNH clone case.

CONCLUSIONS

We succeeded in rallying numerous French-speaking clinical laboratories for both surveys and in harmonizing the technical practice by highlighting common pitfalls.