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Correspondence

Reply

Emory University School of Medicine, Division of Cardiothoracic Surgery

(Email: omar.lattouf{at}emoryhealthcare.org).

To the Editor:

We appreciate the comments of Pappalardo and colleagues [1] regarding the postoperative occurrence of heparin-induced thrombocytopenia (HIT). The authors raise some salient points with which we agree. Specifically, we concur that HIT may be overdiagnosed by the commonly used enzyme-linked immunosorbent assay (EIA), which may lead to inappropriate anticoagulation and unnecessary risk of hemorrhagic complications, particularly in postoperative cardiac surgery patients. However, in the setting of a high pre-test probability, the EIA remains a useful assay. The patients in our study [2] had a high clinical suspicion of HIT (persistently low postoperative platelet count or evidence of thrombosis, or both), rendering the EIA results more valuable. We also share the authors' concern that an incorrect diagnosis of HIT may impact future patient management. When encountering patients with a previous diagnosis of HIT, our practice is to repeat the EIA prior to subsequent procedures that require heparin administration. In this situation, we believe heparin can be used safely if the EIA optical density (OD) level falls below the positive cut-off level for our laboratory.

Until confirmatory functional assays, such as the serotonin release assay or platelet activation assay, become more readily available with faster turnaround times, many hospitals, and laboratories will continue to depend on the EIA. Consequently, it remains important to have objective evidence regarding the EIA and its relationship to outcomes. The use of the EIA is further corroborated by our analysis of the OD values. Our results [2] and previous studies [3] have demonstrated a significant correlation between the OD values obtained from the EIA and the risk of renal failure, thromboembolic events, and mortality.

Finally, we challenge the notion that HIT cannot occur before postoperative day 5. Early HIT developing within 48 hours of heparin administration is well-described and typically occurs in patients with recent heparin exposure [4]. Dismissing a positive EIA result in the early postoperative period, particularly if there is any evidence of thrombosis, may lead to a missed diagnosis of HIT and serious adverse events.

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1. Pappalardo F, Greinacher A, Selleng S. Postoperative complications after cardiac surgery and HIT: a word of caution (letter) Ann Thorac Surg 2008;86:1054-1055.[Free Full Text]
2. Kerendi F, Thourani VH, Puskas JD, et al. Impact of heparin-induced thrombocytopenia on postoperative outcomes after cardiac surgery Ann Thorac Surg 2007;84:1548-1555.[Abstract/Free Full Text]
3. Zwicker JI, Uhl L, Huang WY, et al. Thrombosis and ELISA optical density values in hospitalized patients with heparin-induced thrombocytopenia J Thromb Haemost 2004;2:2133-2137.[Medline]
4. Warkentin TE, Kelton JG. Temporal aspects of heparin-induced thrombocytopenia N Engl J Med 2001;344:1286-1292.[Abstract/Free Full Text]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Faraz Kerendi Vinod H. Thourani John D. Puskas Robert A. Guyton Omar M. Lattouf Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kerendi, F. Articles by Lattouf, O. M. Search for Related Content PubMed Articles by Kerendi, F. Articles by Lattouf, O. M. Related Collections Related Article