Introduction
Advanced chronic liver disease (ACLD) is characterised by complex haemostatic alterations. While thrombocytopenia due to portal hypertension is a well-known phenomenon in ACLD, changes in platelet function remain a topic of ongoing debate and studies are often limited by the use of platelet count-dependent assays.
Aims & Methods
We aimed to investigate whether alterations in platelet function assessed by flow cytometry predict liver disease progression and mortality. Specifically, we prospectively included ACLD patients undergoing hepatic venous pressure gradient (HVPG) measurement and same-day platelet function assessment. Platelet activation was evaluated using flow cytometry by measuring the expression of P-selectin on the platelet surface following stimulation with either (i) protease-activated receptor (PAR)-1 agonist SFLLRN, (ii) PAR-4 agonist AYPGKF or (iii) epinephrin.
Results
107 ACLD patients (age: 55.3 [46.4-62.9] years; 71% male; 59.8% decompensated) with a median HVPG of 18 (12-21) mmHg and a MELD (model for end-stage liver disease) of 11.0 (9.0-14.5) were included.
During a median follow-up of 25.3 (15.7-31.2) months, 29 patients experienced first or further hepatic decompensation, and 17 died. Overall, more pronounced platelet activation in response to SFLLRN (HR per 100 MFI [median fluorescence intensity]: 0.95 [95%CI:0.91-0.99]; p=0.011) and AYPGKF (HR per 100 MFI: 0.93 [95%CI:0.89-0.98]; p=0.005) was linked to a significantly lower risk of first/further decompensation. Importantly, after adjusting for systemic inflammation (i.e., interleukin 6 [IL-6]), portal hypertension (i.e., HVPG) and disease severity (i.e., MELD) in a multivariable Cox regression model (see Table), we observed a significant link between AYPGKF-inducible platelet activation and a reduced risk of decompensation (aHR per 100 MFI: 0.95 [95%CI:0.90-1.00]; p=0.036; model 2), as well as a clear trend for SFLLRN-inducible platelet activation (model 1). Furthermore, increased platelet activation in response to SFLLRN (HR per 100 MFI: 0.92 [95%CI:0.86-0.97]; p=0.006) and AYPGKF (HR per 100 MFI: 0.93 [95%CI:0.87-0.99]; p=0.034) was also linked to an improved transplant-free survival. The prognostic impact of SFLLRN-inducible platelet activation remained significant after adjusting for IL-6 and MELD (aHR: per 100 MFI: 0.93 [95%CI:0.87-1.00]; p=0.040).
During follow-up, portal vein thrombosis (PVT) occurred in 6 patients. Interestingly, increased platelet activation in response to epinephrine was significantly associated with a higher risk of PVT development (HR per 10 MFI: 1.08 [95%CI:1.02-1.14]; p=0.004).
| Univariable analysis
| Multivariable model 1
| Multivariable model 2
|
HR
| 95% CI
| p-value
| aHR
| 95% CI
| p-value
| aHR
| 95% CI
| p-value
|
Response to SFLLRN (PAR-1) (per 100 MFI)
| 0.95
| 0.91-0.99
| 0.011
| 0.97
| 0.93-1.01
| 0.137
|
|
|
|
Response to AYPGKF (PAR-4) (per 100 MFI)
| 0.93
| 0.89-0.98
| 0.005
|
|
|
| 0.95
| 0.90-1.00
| 0.036
|
Response to epinephrin
(per 10 MFI)
| 0.89
| 0.77-1.04
| 0.153
|
|
|
|
|
|
|
MELD (UNOS) (per point)
| 1.11
| 1.03-1.20
| 0.006
| 0.99
| 0.88-1.12
| 0.914
| 0.98
| 0.88-1.10
| 0.756
|
HVPG (per mmHg)
| 1.09
| 1.03-1.16
| 0.003
| 1.06
| 0.99-1.13
| 0.096
| 1.05
| 0.98-1.13
| 0.152
|
Interleukin 6 (per 10 pg/mL)
| 1.30
| 1.13-1.50
| <0.001
| 1.21
| 0.98-1.51
| 0.083
| 1.22
| 0.99-1.50
| 0.057
|
Conclusion
The flow cytometry-based assessment of platelet activation may overcome the impact of a low platelet count, i.e., the primary limitation of platelet function studies in ACLD. Interestingly, higher PAR-1 and PAR-4 mediated platelet activation was independently associated with a reduced risk of hepatic decompensation and an improved transplant-free survival, thus arguing against the recently proposed hypothesis that hyperactive platelets drive disease progression. Finally, increased platelet activation in response to epinephrin was linked to a higher risk of de novo PVT occurrence.
Disclosure
Benedikt Simbrunner: Travel support from AbbVie and Gilead. David JM Bauer: Travel support from AbbVie and Gilead; Speaker fees from AbbVie and Siemens. Philipp Schwabl: Consulting fees from PharmaIN; Travel support from Falk and Phenex Pharmaceuticals. Mattias Mandorfer: Speaker and/or consultant and/or advisory board member for AbbVie, Collective Acumen, Gilead, and W. L. Gore & Associates; Travel support from AbbVie and Gilead. Thomas Reiberger: Grant support from Abbvie, Boehringer-Ingelheim, Gilead, Gore, Intercept, MSD, Myr Pharmaceuticals, Philips Healthcare, Pliant, and Siemens; Speaking honoraria from Abbvie, Gilead, Gore, Intercept, Roche, MSD; Consulting/advisory board fee from Abbvie, Bayer, Boehringer-Ingelheim, Gilead, Intercept, MSD, Siemens; Travel support from Abbvie, Boehringer-Ingelheim, Gilead and Roche. Thomas Gremmel: Speaker fees from Amgen, Bayer, Boehringer-Ingelheim, Bristol Myers Squibb, Daiichi- Sankyo, Novartis, and Pfizer; Grant support from Boehringer-Ingelheim, Bristol Myers Squibb, Medtronic and Abbott.
