Plasma chitotriosidase activity versus CCL18 level for assessing type I Gaucher disease severity: protocol for a systematic review with meta-analysis of individual participant data.

BACKGROUND: Gaucher disease (GD) is an autosomal recessive lysosomal storage disorder caused by deficiency in acid beta-glucosidase. GD exhibits a wide clinical spectrum of disease severity with an unpredictable natural course. Plasma chitotriosidase activity and CC chemokine ligand 18 (CCL18) have been exchangeably used for monitoring GD activity and response to enzyme replacement therapy in conjunction with clinical assessment. Yet, a large-scale head-to-head comparison of these two biomarkers is currently lacking. We propose a collaborative systematic review with meta-analysis of individual participant data (IPD) to compare the accuracy of plasma chitotriosidase activity and CCL18 in assessing type I (i.e., non-neuropathic) GD severity. METHODS: Eligible studies include cross-sectional, cohort, and randomized controlled studies recording both plasma chitotriosidase activity and CCL18 level at baseline and/or at follow-up in consecutive children or adult patients with type I GD. Pre-specified surrogate outcomes reflecting GD activity include liver and spleen volume, hemoglobin concentration, platelet count, and symptomatic bone events with imaging confirmation. Primary studies will be identified by searching Medline (1995 onwards), EMBASE (1995 onwards), and Cochrane Central Register of Controlled Trials (CENTRAL). Electronic search will be complemented by contacting research groups in order to identify unpublished relevant studies. Where possible, IPD will be extracted from published articles. Corresponding authors will be invited to collaborate by supplying IPD. The methodological quality of retrieved studies will be appraised for each study outcome, using a checklist adapted from the Quality Assessment of Diagnostic Accuracy Studies-2 tool. The primary outcome will be a composite of liver volume >1.25 multiple of normal (MN), spleen volume >5 MN, hemoglobin concentration <11 g/dL, or platelet count <100 × 109/L. Effect size estimates for biomarker comparative accuracy in predicting outcomes will be reported as differences in areas under receiver operating characteristic curves along with 95% confidence intervals. Effect size estimates will be reported as (weighted) mean differences along with 95% confidence intervals for each biomarker according to outcomes. IPD meta-analysis will be conducted with both one- and two-stage approaches. DISCUSSION: Valid and precise accuracy estimates will be derived for CCL18 relative to plasma chitotriosidase activity in discriminating patients according to GD severity. SYSTEMATIC REVIEW REGISTRATION: PROSPERO 2015 CRD42015027243

Accurate quantification of fourteen normal bone marrow cell subsets in infants to the elderly by flow cytometry

International audienceStudies of normal bone marrow (BM) cell composition by flow cytometry are scarce. Presently, we aimed to quantify 14 cell subsets from infants to elderly patients

Flow cytometric analysis of neutrophil myeloperoxidase expression in peripheral blood for ruling out myelodysplastic syndromes. A diagnostic accuracy study.

International audienceSuspicion of myelodysplastic syndromes is one of the commonest reasons for bone marrow aspirate in elderly patients presenting with persistent peripheral blood cytopenia of unclear etiology. A peripheral blood assay that accurately rules out myelodysplastic syndromes would have major benefits. The diagnostic accuracy of the intraindividual robust coefficient of variation for neutrophil myeloperoxidase expression measured by flow cytometric analysis in peripheral blood was evaluated in a retrospective derivation study (44 myelodysplastic syndrome cases and 44 controls) and a prospective validation study (68 consecutive patients with suspected myelodysplastic syndromes). Compared with controls, myelodysplastic syndrome cases had higher median robust coefficient of variation values for neutrophil myeloperoxidase expression (40.2% versus 30.9%, P<.001). The area under the receiver operating characteristic curve estimates were 0.94 (95% confidence interval [CI], 0.86-0.97) and 0.87 (95% CI, 0.76-0.94) in the derivation and validation studies, respectively. A robust coefficient of variation lower than 30% ruled out myelodysplastic syndromes with 100% sensitivity (95% CI, 78-100%) and 100% negative predictive value (95% CI, 83%-100%) in the prospective validation study. Neutrophil myeloperoxidase expression measured by flow cytometric analysis in peripheral blood might obviate the need for invasive bone marrow aspirate and biopsy for up to 29% of patients with suspected myelodysplastic syndromes

Accuracy of Chitotriosidase Activity and CCL18 Concentration in Assessing Type I Gaucher Disease Severity. A Systematic Review with Meta-analysis of Individual Participant Data

International audienc

Agreement in continuous intra-individual robust coefficient of variation between simplified and original flow cytometric gating strategies for quantifying peripheral blood neutrophil myeloperoxidase expression (n = 62).

Abbreviations: RCV = robust coefficient of variation.</p

Original flow cytometric gating strategy for quantifying peripheral blood neutrophil myeloperoxidase expression.

CD45+ cells were first individualized by crossing the singlet gate (A), FSC-SSC leukocytes (B), and CD45-positive gate (C). Three populations including granulocytes (CD15+ CD14-), monocytes (CD14+ CD15dim/-), and lymphocytes (CD15- CD14-) were identified (D). Eosinophils were individualized by CD45high CD16 low (E). Mature neutrophils were visualized by [CD15+ CD14-] [CD45low CD16 high] [CD16+ CD11b+] and selected by Boolean intersection: [CD15+ CD14-] [CD16+ CD11b+] with exclusion of [CD45high CD16 low] [CD14+ CD15dim/-] [CD15- CD14-] (F). RCV for MPO was estimated on the MPO gate conditioned on all visualized granulocytes (red dots) without threshold (G). The populations identified were lymphocytes (purple), monocytes (green), eosinophils (orange), MPO mature neutrophils (red). Abbreviations: CD = cluster of differentiation; FSC-A = forward scatter area; FSC-H = forward scatter height; MPO = myeloperoxidase; RCV = robust coefficient of variation; SSC-A = side scatter area; SSC-H = side scatter height.</p

Comparative diagnostic accuracy of intra-individual robust coefficient of variation for peripheral blood neutrophil myeloperoxidase expression between simplified and original flow cytometric gating strategies (n = 55)^a.

Comparative diagnostic accuracy of intra-individual robust coefficient of variation for peripheral blood neutrophil myeloperoxidase expression between simplified and original flow cytometric gating strategies (n = 55)a.</p

Simplified flow cytometric gating strategy for quantifying peripheral blood neutrophil myeloperoxidase expression.

CD45+ cells were first individualized by crossing the singlet gate (A) and CD45 positive gate (B). Population of granulocytes (CD15+ CD14-) was identified (C). Gated cells were selected based on CD16/CD11b double positivity (D) The MPO SSC dot plot (E) was used only to visualize MPO expression of mature neutrophils. The cell population identified was MPO mature neutrophils (red dots). Abbreviations: CD = cluster of differentiation; FSC-A = forward scatter area; FSC-H = forward scatter height; MPO = myeloperoxidase; RCV = robust coefficient of variation; SSC-A = side scatter area; SSC-H = side scatter height.</p