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Mean platelet size related to glycoprotein-specific autoantibodies and platelet-associated IgG.

Javela K, Kekomäki R - Int J Lab Hematol (2007)

Bottom Line: Recent evidence suggests that platelet-associated glycoprotein-specific (GP) antibodies represent true positive autoantibodies and can therefore be taken as the gold standard.Their presence correlated well with increased PA-IgG (R = 0.769).As the PA-IgG displays low specificity compared with the gold standard, its use as such may be abandoned and replaced by tests for platelet-associated GP-specific autoantibodies.

View Article: PubMed Central - PubMed

Affiliation: Finnish Red Cross Blood Service, Helsinki, Finland. kaija.javela@bts.redcross.fi

ABSTRACT
Recent evidence suggests that platelet-associated glycoprotein-specific (GP) antibodies represent true positive autoantibodies and can therefore be taken as the gold standard. Earlier tests, which aimed at detecting platelet-associated IgG (PA-IgG), might have been hampered, e.g. by the variation of platelet size in thrombocytopenic patients. In this study, 206 samples with increased PA-IgG from consecutive thrombocytopenic patients were tested further for GP-specific antibodies with a monoclonal antibody immobilized platelet antigen test (MAIPA) using a combination of a GP IIbIIIa-specific and a GP IbIX-specific antibody for immobilization or, in a separate assay, GP V-specific antibody. Mean platelet size was recorded as forward scatter (FSC) of platelets in flow cytometric analysis of PA-IgG. GP-specific antibodies were detected in 49 (24%) of the 206 patient samples. Their presence correlated well with increased PA-IgG (R = 0.769). The mean platelet size and mean fluorescence intensity (MFI) of PA-IgG were both significantly increased in patients compared with healthy controls (n = 112; P < 0.0001). Notably, PA-IgG was associated with platelet size within the platelet population of both healthy controls and patients (R = 0.999). Further, the probability of GP IIbIIIa and/or IbIX and GP V-specific PA-IgG tended to increase with the mean platelet size of the patients (P = 0.045). In conclusion, large platelets bound more IgG than platelets of normal size, which may explain at least in part the reported low specificity of total PA-IgG measurement. As the PA-IgG displays low specificity compared with the gold standard, its use as such may be abandoned and replaced by tests for platelet-associated GP-specific autoantibodies.

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Platelet populations gated according to platelet size (forward scatter, FSC). Five regions of platelets from a healthy control sample in FSC/SSC (side scatter) dot plot were set: R3 to include 50% of events, both R2 and R4 20%, and R1 and R5 events left outside R2–R4.
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fig02: Platelet populations gated according to platelet size (forward scatter, FSC). Five regions of platelets from a healthy control sample in FSC/SSC (side scatter) dot plot were set: R3 to include 50% of events, both R2 and R4 20%, and R1 and R5 events left outside R2–R4.

Mentions: To analyze if platelets of different size in a single sample had different amounts of PA-IgG, the platelet scatter in FSC/SSC plot was divided into five consecutive gates (R1–R5). Altogether, 54 randomly selected samples were analyzed for PA-IgG using these gates (samples from patients with large, n = 27, with normal, n = 22, and with small platelets, n = 5). R3 was set to include 50% of events and both R2 and R4 20%. R1 and R5 were set to include events outside R2–R4 (Figure 2).


Mean platelet size related to glycoprotein-specific autoantibodies and platelet-associated IgG.

Javela K, Kekomäki R - Int J Lab Hematol (2007)

Platelet populations gated according to platelet size (forward scatter, FSC). Five regions of platelets from a healthy control sample in FSC/SSC (side scatter) dot plot were set: R3 to include 50% of events, both R2 and R4 20%, and R1 and R5 events left outside R2–R4.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2228396&req=5

fig02: Platelet populations gated according to platelet size (forward scatter, FSC). Five regions of platelets from a healthy control sample in FSC/SSC (side scatter) dot plot were set: R3 to include 50% of events, both R2 and R4 20%, and R1 and R5 events left outside R2–R4.
Mentions: To analyze if platelets of different size in a single sample had different amounts of PA-IgG, the platelet scatter in FSC/SSC plot was divided into five consecutive gates (R1–R5). Altogether, 54 randomly selected samples were analyzed for PA-IgG using these gates (samples from patients with large, n = 27, with normal, n = 22, and with small platelets, n = 5). R3 was set to include 50% of events and both R2 and R4 20%. R1 and R5 were set to include events outside R2–R4 (Figure 2).

Bottom Line: Recent evidence suggests that platelet-associated glycoprotein-specific (GP) antibodies represent true positive autoantibodies and can therefore be taken as the gold standard.Their presence correlated well with increased PA-IgG (R = 0.769).As the PA-IgG displays low specificity compared with the gold standard, its use as such may be abandoned and replaced by tests for platelet-associated GP-specific autoantibodies.

View Article: PubMed Central - PubMed

Affiliation: Finnish Red Cross Blood Service, Helsinki, Finland. kaija.javela@bts.redcross.fi

ABSTRACT
Recent evidence suggests that platelet-associated glycoprotein-specific (GP) antibodies represent true positive autoantibodies and can therefore be taken as the gold standard. Earlier tests, which aimed at detecting platelet-associated IgG (PA-IgG), might have been hampered, e.g. by the variation of platelet size in thrombocytopenic patients. In this study, 206 samples with increased PA-IgG from consecutive thrombocytopenic patients were tested further for GP-specific antibodies with a monoclonal antibody immobilized platelet antigen test (MAIPA) using a combination of a GP IIbIIIa-specific and a GP IbIX-specific antibody for immobilization or, in a separate assay, GP V-specific antibody. Mean platelet size was recorded as forward scatter (FSC) of platelets in flow cytometric analysis of PA-IgG. GP-specific antibodies were detected in 49 (24%) of the 206 patient samples. Their presence correlated well with increased PA-IgG (R = 0.769). The mean platelet size and mean fluorescence intensity (MFI) of PA-IgG were both significantly increased in patients compared with healthy controls (n = 112; P < 0.0001). Notably, PA-IgG was associated with platelet size within the platelet population of both healthy controls and patients (R = 0.999). Further, the probability of GP IIbIIIa and/or IbIX and GP V-specific PA-IgG tended to increase with the mean platelet size of the patients (P = 0.045). In conclusion, large platelets bound more IgG than platelets of normal size, which may explain at least in part the reported low specificity of total PA-IgG measurement. As the PA-IgG displays low specificity compared with the gold standard, its use as such may be abandoned and replaced by tests for platelet-associated GP-specific autoantibodies.

Show MeSH