Table 1.
Characteristics of included studies
| Reference (first author and year) | Study design | N | Study population | Pretest clinical scoring system | Immunoassay for screening HIT | Platelet activation assay for confirming HIT | Suspected HIT/confirmed HIT | Proportion of ICU or critical illness | Heparin administration in confirmed HIT |
|---|---|---|---|---|---|---|---|---|---|
| Riker26 2020 | Case report | 16 | Thrombocytopenia with anti-PF4 Ab among intubated COVID-19 patients with ARDS | 4T score | ELISA | SRA | 3/1 | 16 (100%) | 2 prophylactic UFH/LMWH and 1 therapeutic UFH |
| Lingamaneni27 2020 | Case report | 5 | COVID-19 patients with HIT suspicion | 4T score | ELISA | SRA | 5/1 | 5 (100%) | All 5 received therapeutic heparin |
| May28 2020 | Case report | 7 | Hospitalized COVID-19 patients with positive anti-platelet factor 4 Ab | 4T score | ELISA | SRA | 7/1 | 7 (100%) | 3 prophylactic UFH, 3 prophylactic LMWH and 1 prophylactic LMWH/UFH |
| Patell29 2020 | Retrospective cohort | 88 | patients hospitalized with Covid-19 and received intravenous UFH for ≥5 d |
4T score | Latex immune turbidimetric assay | SRA | 8/3 | NR | All 3 confirmed HIT received therapeutic UFH |
| Bidar30 2020 | Case report | 2 | Confirmed HIT in COVID-19 patients with severe ARDS on VVECMO | NR | ELISA | HIPA | 2/2 | 2 (100%) | All 2 confirmed HIT received therapeutic UFH |
| Tran31 2020 | Case report | 1 | A patient with SARS-CoV-2 pneumonitis and confirmed HIT | 4T score | ELISA | HIPA | 1/1 | 1 | The patient with confirmed HIT received prophylactic LMWH |
| Daviet32 2020 | Retrospective cohort | 86 | COVID-19 ARDS in 2 ICUs enrolled in COAG-COVID trial | 4T score | Quantitative CIA; IgG specific | HIPA | NR/7 | 86 (100%) | All 7 confirmed HIT received therapeutic LMWH or UFH |
| Delrue33 2020 | Retrospective cohort | 626 | All consecutive SARS-CoV-2-infected adults admitted to the ICU and medical wards | 4T score | PaGIA, ELISA IgG | HIPLA, SRA | 10/1 | 184 (29.4%) | Of 10 HIT suspicions, 2 received UFH, 1 received LMWH and 7 received LMWH followed by UFH |
| Helms34 2020 | Prospective cohort | 150 | All patients with SARS-CoV-2 ARDS admitted to the ICU | NR | NR | NR | 4/0 | 150 (100%) | 150 (100%); 105 (70%) prophylactic doses; 45 (30%) therapeutic doses |
| Ionescu35 2020 | Retrospective cohort | 3480 (2574 receiving LMWH or UFH) | Consecutive COVID-19 adult patients hospitalized within 8 hospitals located in Southeast Michigan | NR | NR | NR | NR/12 | 642 (18.4%) | 1156 with prophylactic LMWH; 699 with received prophylactic UFH; 424 with therapeutic LMWH and 295 with therapeutic UFH |
| Santi36 2020 | Retrospective cohort | 94 | Hospitalized patients infected with COVID-19 |
NR | NR | NR | NR/2 | NR | 2 received therapeutic UFH |
| Warrior37 2020 | Retrospective cohort | 1265 | Hospitalized COVID-19 positive patients | 4T score | ELISA | SRA | 8/1 | NR | Of 8 HIT suspicions, 4 received LMWH, 2 received UFH and 2 received LMWH followed by UFH |
| Madala38 2021 | Case report | 1 | A patient with SARS-CoV-2 pneumonia and ischemic stroke | 4T score | ELISA | SRA | 1/1 | 1 | The patient with confirmed HIT received UFH followed by LMWH |
| Julian39 2021 | Case report | 1 | A patient with COVID-19 positive and confirmed autoimmune HIT | N/A | ELISA | SRA | 1/1 | 1 | No heparin exposure before documented thrombosis and thrombocytopenia |
| Lawler40 2021 | Randomized controlled trial | 2231 | Non-critically ill patients hospitalized for Covid-19 |
4T score | ELISA | SRA | NA/0 | 0 | 1181 received therapeutic- and 1050 received prophylactic-dose anticoagulation; no confirmed HIT |
Ab, antibody; CIA, chemiluminescent immunoassay; ELISA (or EIA), enzyme-linked immunosorbent assay (or enzyme immunoassay); ICU, intensive care unit; NR, not reported; PaGIA, particle gel immunoassay.