Plasma Cholinesterase Activity in ITP Patients with/without Thrombosis.

In the process of immune mediated destruction, platelets may become activated and release procoagulant microparticles in ITP (Immune Thrombocytopenic Purpura). Although bleeding is common manifestation, some patients with ITP may suffer thrombotic complications, often presenting with TIA like syndromes. Brain MRI revealed findings consistent with ischemic small vessel disease in this subgroup (J Lab Clin Med 119: 334, 1992, Thromb Res 107:337, 2002). Recently acetylcoholinesterase (AChE) of RBC and/or non-specific plasma cholinesterase (ChE) was reported to be associated with the inflammation of blood vessels and may be a marker of some inflammatory states. In the present study we investigated plasma ChE activity in patients with ITP with or without thrombotic complication.

(i) Patients. We measured ChE activity in 49 patients with ITP. They were sub-grouped as having thrombosis (TBS), F/M (11/7), and non-thrombosis (Non-TBS), F/M (23/8). The TBS group included 9 with TIA like syndrome, 6 with CAD and 3 with venous thrombosis. (ii) Assay of ChE was essentially by Ellman's method. In our system, milli-absorbance units/min (mA/min) x 0.065 = umols substrate cleaved/min. Values reported here are in units of mA/min per mL plasma. Normal controls (NC, n=14) had a cutoff of 3000 mA/min per mL plasma (=mean +2SD). (iii) Sample handling. Platelet-poor plasma (PPP) was prepared by centrifuging 10 min at 1800 xg, then frozen in aliquots. For assay, it was diluted 1:20 with saline, then 5 uL and 10 uL were used in 96-well microtiter plate.

(i) We observed higher level of ChE in the TBS group compared to Non-TBS in ITP. The TBS group (+/- SD) had mean value 2859 ±866, while the Non-TBS group had 2267 ±777 (units as above). This difference was significant, p<0.02. (ii) In TBS groups, we compared TIA subgroup with other TBS subgroup and observed that the n=9 patients with TIA had higher activity compared to the other TBS: 3250 vs 2466 mA/min per mL plasma. However, this difference did not reach significance in this small patient population. Further, 5/9 TIA patients (66%) had ChE activities >3000 (normal cutoff values) compared to only 2/9 (22%) of those with other TBS >3000.

(i) The ChE activity of ITP patients with TBS is significantly increased compared to Non-TBS in ITP patients. It has been suggested that Blood ChE/AChE may reflect some inflammatory, prothrombotic states. (ii) ITP patients with TIA exhibited higher ChE activity among TBS subgroups in ITP, suggesting that ChE activity may serve as a useful biomarker in TIA like syndrome associated with ITP. However, further study in a larger number of patients is needed to confirm these preliminary findings.

No relevant conflicts of interest to declare.