Heparin induced thrombocytopenia (hit) syndrome in adult patients at Kenyatta National Hospital Kenya.

Abstract

Background: Heparin is a commonly used anticoagulant in Kenyatta National Hospital (KNH). Besides bleeding complications heparin induced thrombocytopenia (HIT) with thrombosis, commonly reffered to as HIT syndrome is a well recognized complication of heparin therapy. Some of the patients with HIT may experience other unusual complications such as skin necrosis and anaphylactic reactions which are considered as manifestations of HIT syndrome. HIT antibody with a prevalence of about 8% has been elucidated to be the main pathogenic antibody in the pathophysiology of HIT and skin necrosis, and has been associated with anaphylactic reactions though mechanisms have not been established. There is no documented data on the occurrence of these complications in KNH. Study design: This was a cross sectional study. Objectives: The study was aimed at screening for the presence of Heparin induced thrombocytopenia (H IT) and its associated unusual complications of skin necrosis and anaphylactic reactions. Study area: The study was conducted at Kenyatta National Hospital (KNH) - Nairobi, the major referral hospital in the country and the Haematology and Immunology units of the school of medicine- University of Nairobi. Study population: The study involved 188 adults inpatients of both sexes aged 18 years and above on heparin therapy in medical, obstetric, orthopaedic and cardiothoracic surgical wards at Kenyatta National Hospital from April 2009 to August 2009. Materials and methods: Data collection was carried out through clinical history taking and physical examination of the patients, review of patient's medical records, and laboratory tests (total blood count by automated cell counter - cell Dyn 1300, peripheral blood film and H.1. antibody detection by ELISA - ZYMUTEST HIA IgG). All the information was entered in a questionnaire. Data analysis was aided by a computer (SPSS version 15), Chi-square test and Fisher's exact test were used for correlation between variables and a p-value of < 0.05 was considered to yield a statistical significant result. Results: Of 22,592 adult inpatients admitted to the KNH in the period of April to August 2009 a total of 294 patients on heparin were recruited, and of these 188 patients were followed up for thrombocytopenia, skin necrosis and anaphylactic reactions. The majority of study patients (58%) were female and (42%) were male. The highest proportions (16.5%) of the patient were aged between 30-34 years while the age bracket 55-59 years had the least number of patients (3.7%). A large proportion of patients were from the medical ward (59%). Most of the patients (72.90%) were on UFH (heparin sodium) preparation. The overall prevalence of HIT was 2.70% (3.65% with UFH and 0% with LMWH). All the 5 (2.7%) of the study patients who had HIT were female, from the medical unit and were all on UFH preparation. There was no statistically significant difference in the HIT status between - the two heparin preparations, UFH and LMWH (enoxaparin) (p-value 0.167); and the different patient populations (p-value 0.313). Heparin induced skin necrosis and anaphylactic reactions were not seen in any of the study patients that were followed up for a total of seven (7) or ten (10) days. Of the total study patients, the overall prevalence of heparin induced antibody which is associated with the risk of developing these complications was 17%, (18.20% with UFH and 13.70% with LMWH). Medical ward patients had the highest frequency of antibody formation (21.60%) with the least in obstetric patients (5.90%). There was no statistically significant difference in the heparin induced antibody positivity between - the two heparin preparations, UFH and LMWH (p-value 0.463) and between the different patient categories (p-value 0.214). Conclusion This study shows that Heparin induced thrombocytopenia (HIT) syndrome is rare in KNH. Heparin induced thrombocytopenia (HIT) was found at a low prevalence of 2.7%, and appeared to occur mainly in medical patients and in those on UFH preparation. The unusual complications of HIT (skin necrosis and anaphylactic reactions) are uncommon at KNH. Heparin induced antibody (HIA) which is associated with the risk of developing these complications was found at a low prevalence (17%), and appear to predominate in medical patients and in those who were on UFH preparation. However as the validation of the HIT antibody test and some of the steps in the interpretation of the HIT antibody test (inhibition of a positive result by high concentration of heparin) were not performed, there is a probability that the prevalence of this antibody could be much lower. With the low prevalence of HIT and the shortcomings of this study, routine laboratory screening for detection of the HIT antibody may not be justified, further studies will need to be done. Recommendations Although the study shows that HIT, skin necrosis and anaphylactic reactions are rare in KNH it is still advised to perform a close clinical and laboratory surveillance of platelet count in all patients on therapeutic or prophylactic doses of UFH. Further studies especially in various patient population-specific groups are needed for a proper approximation of the prevalence of these complications. More advanced studies on HIT are recommended which will involve adequate laboratory investigations to exclude other causes of thrombocytopenia, measures to confirm thrombosis (Doppler ultrasonography, venography) and probably longer duration of follow up to enable proper approximation of the prevalence of HIT and skin necrosis.