The effect of obesity on the rate of heparin-induced thrombocytopenia.

: Heparin-induced thrombocytopenia (HIT) occurs in patients receiving heparin-containing products due to the formation of platelet-activating antibodies to heparin and platelet factor 4. Diagnosis includes utilization of a scoring system known as the 4-T score, and HIT laboratory assays. Recently, obesity was identified as a potential factor associated with the development of HIT. The objective of this study was to evaluate the association of HIT with obesity in ICU and general medicine patients. We performed a chart review of adult patients within the Methodist Healthcare System, and included patients who had an ELISA and serotonin release assay laboratory tests reported within same hospital admission in which they also had documented receipt of heparin. Obese patients were compared with nonobese patients (BMI < 30) for the primary outcome of HIT occurrence, and secondary outcomes including rate of thrombosis, 4-T scores, and ELISA optical density values. We also generated a 5-T score by including one additional point for those with a BMI of 30 or more to determine the predictive value of this score in identifying HIT. Obesity was confirmed to be a risk factor for HIT, and the 5-T score model was also predictive of the development of HIT. However, the 5-T score was not statistically more predictive of HIT than the 4-T score. Predicting HIT remains challenging and novel markers of HIT are needed to improve HIT recognition. Although obesity did not improve the 4-T score, it may improve the predictability of other scoring systems, and further investigation is warranted.