Abstract Number: PB1424
Meeting: ISTH 2020 Congress
Background: Diagnosing heparin induced thrombocytopenia (HIT) in patients with end stage renal disease (ESRD) can be difficult as they are frequently exposed to heparin and have multiple etiologies for thrombocytopenia.
Aims: To correlate 4T scores, PF4 ELISA results, and serotonin release assays (SRA) in patients with ESRD.
Methods: A retrospective review of patients with ESRD (CrCl < 15 mL/min or on renal replacement therapy (RRT), with IgG heparin-PF4 ELISA testing between October 2015-- September 2019 was performed. Baseline characteristics, route and type of heparin, type of RRT, calculated 4T scores, PF4 and SRA results were collected. False positive PF4s were defined as a positive PF4 with a negative SRA, low 4T score, or lack of treatment for HIT. True positive PF4 results required intermediate to high 4T score, positive SRA, and treatment for HIT. Indeterminate cases were classified based on clinical treatment.
Results: Of 265 patients with ESRD (92% on RRT), 29 patients (10.9%) had a positive PF4. Eleven had confirmed diagnosis of HIT: 10 with 4T >4, positive SRA, one with 4T of 6 and PF4 of 1.947 but no SRA; all were treated for HIT. False positive PF4 values occurred in 8 patients (27.5%) with negative SRA, 4T < 4, and not treated for HIT. Of 10 patients with negative SRA but intermediate-high 4T and positive PF4, only 3 were treated for HIT. Fifteen (51.7%) patients with negative SRA were not diagnosed and treated as HIT despite positive PF4 and intermediate-high 4T.
Conclusions: In ESRD patients, PF4 results and 4T scores did not consistently correlate with a clinical diagnosis of HIT. Patients with intermediate-high 4Ts and PF4 > 1.0 had negative SRAs and were not treated for HIT with no adverse outcomes. PF4 testing and 4T scores may not be accurate in this population.
| Type of Heparin Exposure (n=265) | n (%) |
| Unfractionated heparin only; Low molecular weight heparin only (LMWH); Combination of unfractionated heparin and LMWH; No heparin while inpatient | 214 (80.8); 1 (0.4); 25 (9.4); 25 (9.4) |
| Route of heparin (n=240) | n (%) |
| Subcutaneous; Intravenous; Flushes; Combination; Other | 106 (44.2; 77 (32.1); 6 (2.5; 42 (17.5); 9 (3.7) |
| End Stage Renal Disease (n=265) | n (%) |
| CrCl<15 mL/min not on renal replacement therapy; Continuous renal replacement therapy; Hemodialysis; Peritoneal dialysis | 21 (7.9); 99 (37.4); 143 (54.0); 2 (0.7) |
[Table 1 Key Baseline Characteristics]
| IgG ELISA PF4 OD | SRA Negative (n=18) | SRA Positive (n=10) |
| OD 0.4-0.8 n(%); OD 0.4-1.0 n(%); OD>1.0 n(%) | 9 (50); 12 (67); 6(33) | 1 (10); 2 (20); 8 (80) |
| 4T Scores | SRA Negative (n=18) | SRA Positive (n=10) |
| Low Suspicion (/=6) | 8( 44); 6 (33); 4 (22) | 1(10); 6 (60); 3 (30) |
| PF4 Result by 4T score | PF4 OD 0.4-1.0 (n=12) | PF4 OD > 1.0 (n =6) |
| Low Suspicion HIT (0-3); Intermediate Suspicion HIT (4-5); High Suspicion HIT (>5) | 7 (58.3); 2 (16.7); 3 (25.0) | 1 (16.7); 4 (66.7); 1 (16.7) |
[Table 2 Clinical and Laboratory Results for Suspected HIT]
To cite this abstract in AMA style:
Kelly J, Rimsans J, Sylvester K, Ting C, Bernier T, Connors JM. Evaluation of 4T Probability Scores, Heparin PF4 Antibody, and Serotonin Release Values in End Stage Renal Disease Patients in the Assessment of Heparin Induced Thrombocytopenia [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/evaluation-of-4t-probability-scores-heparin-pf4-antibody-and-serotonin-release-values-in-end-stage-renal-disease-patients-in-the-assessment-of-heparin-induced-thrombocytopenia/. Accessed August 15, 2022.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/evaluation-of-4t-probability-scores-heparin-pf4-antibody-and-serotonin-release-values-in-end-stage-renal-disease-patients-in-the-assessment-of-heparin-induced-thrombocytopenia/