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Evaluating Four HIT Prediction Scores After Cardiac Surgery With Cardiopulmonary Bypass: A Comparative Study
Guillaume Soyer1, Philippe Savard2, Philippe Guerci3
1Department of CardioThoracic and Vascular Anesthesiology and Critical Care, University Hospital of Nancy, France.
Insights
Clinical scores for heparin-induced thrombocytopenia (HIT) show similar diagnostic performance in cardiac surgery patients. These scores are valuable for ruling out HIT due to their high negative predictive value.
Area of Science:
- Cardiology
- Hematology
- Clinical Diagnostics
Background:
- Heparin-induced thrombocytopenia (HIT) is a serious immune complication of heparin therapy.
- Accurate diagnosis of HIT is crucial, especially in high-risk populations like cardiac surgery patients undergoing cardiopulmonary bypass (CPB).
- Clinical prediction scores are used to estimate HIT probability, but their performance in the CPB setting is not well-defined.
Purpose of the Study:
- To compare the diagnostic accuracy of four established clinical prediction scores for HIT.
- To evaluate the utility of these scores in adult patients who underwent cardiac surgery with CPB.
Main Methods:
- A bicentric retrospective observational study was conducted in France.
- Adult patients (2014-2021) who underwent cardiac surgery with CPB and were tested for HIT postoperatively were included.
- Diagnostic performance was assessed using receiver operating characteristic (ROC) curves and compared statistically.
Main Results:
- Among 283 patients, 19% were HIT-positive. Areas under the ROC curve for the 4Ts, HIT Expert Probability, cardiopulmonary bypass, and HFH scores ranged from 0.79 to 0.86, with no significant differences.
- Negative predictive values were high (94-96%), while positive predictive values were modest (31-49%).
- HIT-positive patients showed a biphasic platelet count pattern and higher mortality rates.
Conclusions:
- No single clinical probability score demonstrated superior diagnostic performance for HIT in cardiac surgery patients with CPB.
- These scores are most valuable as rule-out tools due to their high negative predictive performance.
- Further research is needed to develop and validate HIT diagnostic strategies specifically for the cardiac surgery population.
Objectives:
To compare the diagnostic performance of 4 clinical prediction scores for heparin-induced thrombocytopenia (HIT) in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB).
Design:
Bicentric retrospective observational study.
Setting:
Two tertiary university hospitals in France.
Participants:
Adult patients who underwent cardiac surgery with CPB between 2014 and 2021 and for whom HIT testing was requested during the postoperative period.
Interventions:
None.
Measurements And Main Results:
HIT diagnosis was established using a standardized approach combining anti-platelet factor 4/heparin IgG enzyme-linked immunosorbent assay, a functional platelet activation test, and multidisciplinary clinical adjudication. Among 283 patients investigated for suspected HIT, 55 (19%) were classified as HIT-positive. The diagnostic performance of 4 clinical probability scores, the 4Ts score, the HIT Expert Probability score, the cardiopulmonary bypass score, and the Groupe Français d'Étude sur l'Hémostase et la Thrombose score, was assessed using receiver operating characteristic (ROC) curves and formally compared using the DeLong nonparametric test for correlated ROC curves. Areas under the ROC curve ranged from 0.79 (cardiopulmonary bypass) to 0.86 (HIT Expert Probability), with no statistically significant differences observed between scores. Using optimized thresholds, negative predictive values ranged from 94% to 96%, whereas positive predictive values remained modest (31%-49%). HIT-positive patients exhibited a characteristic biphasic platelet count pattern, with an initial postoperative decline followed by a delayed second nadir around postoperative day 10. Among HIT-positive patients, the 30-day and 1-year mortality rates were 9.1% and 14.5%, respectively. Median intensive care unit and hospital lengths of stay were 11 [6-18] and 23 [18-32] days.
Conclusions:
In patients undergoing cardiac surgery with CPB, no clinical probability score has demonstrated clear superiority for the diagnosis of HIT. Their principal clinical value lies in their high negative predictive performance, supporting their use as rule-out tools. Diagnostic strategies specifically tailored to the cardiac surgery setting remain needed and warrant prospective validation.
