title: Incidence and diagnosis of heparin-induced thrombocytopenia (HIT) in patients with traumatic injuries treated with unfractioned or low-molecular-weight heparin: a literature review.
abstract: BACKGROUND
  The incidence of thromboembolic complications after major traumatic injuries is high (>50%). Thromboprophylaxis, often by low-molecular-weight heparin (LMWH) or unfractioned heparin (UH) is therefore routinely administered. Thromboprophylaxis is also advised after immobilisation for isolated lower leg injuries. Heparin induced thrombocytopenia (HIT) is a rare but very serious immune mediated complication of treatment with LMWH, which can cause potentially fatal thromboembolism. In the general medical and surgical population the incidence of HIT is 0.2%. Little is known about the incidence of HIT and value of screening in trauma patients and in isolated lower extremity injuries. Therefore, we performed a systematic literature review.
  
  
  METHODS
  The online databases Medline and EMBASE were searched independently by two authors. Manuscripts were selected for analysis by quantitative and qualitative selection. After eliminating duplicate articles and irrelevant studies, seven relevant papers reporting on the incidence of HIT in trauma patients were identified and two studies reported the incidence of HIT in patients with lower leg injuries.
  
  
  RESULTS
  The selected papers varied in study design: three randomised controlled trials, three cohort studies and one case report were identified. The methodological quality of the studies varied. In a total population of 1920 patients, HIT was identified in seven patients (0.36%). Pooling of data was impossible due to heterogeneity in study design and populations. No HIT was reported in 826 patients with lower extremity injuries, requiring immobilisation.
  
  
  CONCLUSIONS
  Only a few studies have reported on the incidence of HIT in trauma patients who receive prophylactic LMWH. In the heterogenous populations of the available studies, the incidence of HIT appears to be very low and comparable to other patient populations. There is hardly any literature on the incidence of HIT in patients with isolated lower leg injuries receiving LMWH, but incidence seems to be very low.
  
  
  CONCLUSIONS
  The incidence of HIT in trauma patients who receive LMWH thromboprophylaxis appears to be low (0.36%). Incidence of HIT in patients with isolated lower leg injuries receiving LMWH seems very low. Monitoring of platelet count could be considered in hospitalised patients with a high risk for development of HIT. A pre-test scoring system may identify these patients.
authors.affiliation: Department of Surgery and Orthopaedic Surgery, VieCuri Medical Centre, Tegelseweg 210, 5912 BL Venlo, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Bloemen
authors.forename: M J G
authors.initials: MJ
authors.lastname: Testroote
authors.forename: M L G
authors.initials: ML
authors.lastname: Janssen-Heijnen
authors.forename: H M J
authors.initials: HM
authors.lastname: Janzing
mesh_terms: D000925:Anticoagulants / Q000009:adverse effects* / Q000627:therapeutic use; D015331:Cohort Studies; D006495:Heparin, Low-Molecular-Weight / Q000009:adverse effects* / Q000627:therapeutic use; D006801:Humans; D015994:Incidence; D007866:Leg; D035002:Lower Extremity / Q000293:injuries*; D010976:Platelet Count; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000175:diagnosis* / Q000453:epidemiology; D014947:Wounds and Injuries / Q000150:complications* / Q000188:drug therapy*
chemical_list: D000925:Anticoagulants; D006495:Heparin, Low-Molecular-Weight