American Society of Hematology

Figure 2.

$A significant number of diagnostic HIT samples contain remnant heparin, and treatment with heparinase I can change the diagnosis from “aHIT” to “conventional” HIT. (A) Anti-Xa activity in diagnostic samples was quantified in citrated plasma samples obtained from 30 patients with suspected HIT and tested in the conventional SRA (0.1 U/mL unfractionated heparin). Diamonds represent SRA-negative samples (<20% serotonin release in the conventional SRA), squares represent SRA-indeterminate samples (≥20% in the conventional SRA with <50% inhibition with a high concentration of heparin (100 U/mL), and circles depict SRA-positive samples (≥20% in the conventional SRA with >50% inhibition with 100 U/mL heparin). SRA-positive samples with detectable anti-Xa activity are depicted by solid red circles, whereas those without are shown as solid purple circles. (B) No-heparin SRA testing was performed on nine conventional SRA-positive samples. For each sample, untreated (solid circles) and heparinase I-treated (open circles) no-heparin SRA results are depicted and connected by a line. (C) Two spontaneous HIT patient samples were tested in the conventional SRA (0.1 units/mL unfractionated heparin; open triangles) or in the no-heparin SRA (closed triangles). (D) Unfractionated heparin or (E) Enoxaparin (LMWH) was spiked into a classical HIT sample (conventional SRA-positive; no-heparin SRA-negative) at concentrations indicated on the x-axes, and conventional SRA (0.1 U/mL UFH; blue line) or no-heparin SRA (red line) testing was performed. (F) P-selectin expression was quantified via flow cytometry after washed platelets were incubated with a healthy donor (NC, normal control) or classical HIT sample (HIT) spiked with the indicated concentration of unfractionated heparin (indicated on the X-axis) with or without heparinase I treatment. P-selectin expression results were compared using 2-way analysis of variance. (G) Serum samples drawn from a patient with HIT >12 hours after heparin cessation, or three other patients with HIT <4 hours after heparin cessation were treated with buffer (blue) or heparinase I (red) and evaluated in the no-heparin SRA.$

A significant number of diagnostic HIT samples contain remnant heparin, and treatment with heparinase I can change the diagnosis from “aHIT” to “conventional” HIT. (A) Anti-Xa activity in diagnostic samples was quantified in citrated plasma samples obtained from 30 patients with suspected HIT and tested in the conventional SRA (0.1 U/mL unfractionated heparin). Diamonds represent SRA-negative samples (<20% serotonin release in the conventional SRA), squares represent SRA-indeterminate samples (≥20% in the conventional SRA with <50% inhibition with a high concentration of heparin (100 U/mL), and circles depict SRA-positive samples (≥20% in the conventional SRA with >50% inhibition with 100 U/mL heparin). SRA-positive samples with detectable anti-Xa activity are depicted by solid red circles, whereas those without are shown as solid purple circles. (B) No-heparin SRA testing was performed on nine conventional SRA-positive samples. For each sample, untreated (solid circles) and heparinase I-treated (open circles) no-heparin SRA results are depicted and connected by a line. (C) Two spontaneous HIT patient samples were tested in the conventional SRA (0.1 units/mL unfractionated heparin; open triangles) or in the no-heparin SRA (closed triangles). (D) Unfractionated heparin or (E) Enoxaparin (LMWH) was spiked into a classical HIT sample (conventional SRA-positive; no-heparin SRA-negative) at concentrations indicated on the x-axes, and conventional SRA (0.1 U/mL UFH; blue line) or no-heparin SRA (red line) testing was performed. (F) P-selectin expression was quantified via flow cytometry after washed platelets were incubated with a healthy donor (NC, normal control) or classical HIT sample (HIT) spiked with the indicated concentration of unfractionated heparin (indicated on the X-axis) with or without heparinase I treatment. P-selectin expression results were compared using 2-way analysis of variance. (G) Serum samples drawn from a patient with HIT >12 hours after heparin cessation, or three other patients with HIT <4 hours after heparin cessation were treated with buffer (blue) or heparinase I (red) and evaluated in the no-heparin SRA.

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