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Venous Thromboembolism Risk Stratification and Chemoprophylaxis: A Meta-Analysis Finds No Benefit, More Risk

Swanson, Eric MD

Plastic and Reconstructive Surgery – Global Open: June 2017 - Volume 5 - Issue 6 - p e1356
doi: 10.1097/GOX.0000000000001356
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United States

From the Swanson Center, Leawood, Kans.

Disclosure: The author has no financial interest to declare in relation to the content of this article. The Article Processing Charge was paid for by the author.

Eric Swanson, MD, Swanson Center, 11413 Ash Street, Leawood, KS 66211, E-mail: eswanson@swansoncenter.com

This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

Caprini scores and routine anticoagulation are promoted to reduce venous thromboembolism (VTE) risk in a meta-analysis published recently in Annals of Surgery.1 However, factual errors beg disclosure.

Pannucci et al.1 reported a 2.45% (149/6,085) overall VTE risk for patients who did not receive chemoprophylaxis but did not report the 4.37% (380/8,691) risk for patients who did receive chemoprophylaxis (P < 0.0001). According to Figure 4, the VTE rate for patients with Caprini scores of 5 and 6 was significantly greater for anticoagulated patients (3.54% versus 1.85%; P < 0.001).1 For patients with Caprini scores of 7 and 8, the VTE risks were 5.37% for patients receiving chemoprophylaxis versus 4.02% for untreated patients, not significantly reduced for anticoagulated patients, as claimed.1 Among patients with Caprini scores ≥ 5, the VTE risk was significantly greater (P < 0.001) for anticoagulated patients (comparisons performed using a chi-square test2).

One of the studies included in the meta-analysis, by Jeong et al.,3 reported 19 VTEs among 574 plastic surgery patients who received chemoprophylaxis and only 5 VTEs among 1,024 patients who did not receive chemoprophylaxis (P < 0.00001). These numbers are much different from those reported in the meta-analysis (5/238 and 3/301, respectively).1 Correcting this error reduces the P value (already < 0.0001) favoring the untreated patients to essentially zero.2

Pannucci et al.1 reported that anticoagulated plastic surgery inpatients with Caprini scores of 7 to 8 or > 8 have a significant VTE risk reduction. However, the referenced study found that these differences were not significant (P = 0.230 and 0.182, respectively).4 Moreover, a subsequent review by the same lead author found no significant difference in VTE risk (P = 0.08) for plastic surgery inpatients when compared by Caprini scores but a higher risk of bleeding (P = 0.02) in anticoagulated patients.5 The bleeding risk was also significantly increased (P = 0.006) in the recent meta-analysis,1 contradicting a previous study that found no significant difference.6

The title references risk in surgical patients, but the authors included 1,176 nonsurgical patients.7,8 The authors report poor comparability scores.1 A bewildering number of confounding variables undermines the comparisons. These include a cancer diagnosis, having surgery, the type of surgery, anesthesia, the method of VTE diagnosis, follow-up interval, sequential compression devices, whether upper-extremity thromboses and superficial thromboses are included, and the method of evaluating the 40 parameters that make up a Caprini score. Retrospectively evaluating Caprini scores based on chart reviews or insurance billing information is unreliable.9 For example, Obi et al.7 recorded only 1 patient with a history of varicose veins among 4,844 patients admitted to an intensive care unit. Pannucci et al.1 did not report the results of their funnel plot analysis to evaluate publication bias. The selected articles share a bias for chemoprophylaxis. One study grouped patients according to “appropriate” and “inappropriate” prophylaxis and called failure to administer chemoprophylaxis “malpractice.”10

The false-positive rate for individual risk stratification is consistently 97% and almost half of the affected patients are missed using Caprini scores ≥ 7 as a cutoff.11 This method can hardly be considered “precision medicine” or capable of predicting VTE risk, as claimed.1 In evaluating the American Association for Accreditation of Ambulatory Surgery Facilities data for 354,969 abdominoplasties, Keyes (Personal communication, February 7, 2017) finds Caprini scores unhelpful because 135 (67.5%) of the 200 VTEs occurred in patients with Caprini scores < 5. The evidence-based surgeon will make treatment choices based on the facts, not the conventional wisdom.

Facts are stubborn things. —John Adams.

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REFERENCES

1. Pannucci CJ, Swistun L, MacDonald JK, et alIndividualized venous thromboembolism risk stratification using the 2005 Caprini score to identify the benefits and harms of chemoprophylaxis in surgical patients: a meta-analysis. Ann Surg. 2017;265(6):1094–1103.
2. Calculation for the chi-square test. Available at http://www.quantpsy.org/chisq/chisq.htm. Accessed April 2, 2017.
3. Jeong HS, Miller TJ, Davis K, et alApplication of the Caprini risk assessment model in evaluation of non-venous thromboembolism complications in plastic and reconstructive surgery patients. Aesthet Surg J. 2014;34:87–95.
4. Pannucci CJ, Dreszer G, Wachtman CF, et alPostoperative enoxaparin prevents symptomatic venous thromboembolism in high-risk plastic surgery patients. Plast Reconstr Surg. 2011;128:1093–1103.
5. Pannucci CJ, MacDonald JK, Ariyan S, et alBenefits and risks of prophylaxis for deep venous thrombosis and pulmonary embolus in plastic surgery: a systematic review and meta-analysis of controlled trials and consensus conference. Plast Reconstr Surg. 2016;137:709–730.
6. Pannucci CJ, Wachtman CF, Dreszer G, et alThe effect of postoperative enoxaparin on risk for reoperative hematoma. Plast Reconstr Surg. 2012;129:160–168.
7. Obi AT, Pannucci CJ, Nackashi A, et alValidation of the Caprini venous thromboembolism risk assessment model in critically ill surgical patients. JAMA Surg. 2015;150:941–948.
8. Gharaibeh L, Albsoul-Younes A, Younes NEvaluation of venous thromboembolism prophylaxis after the introduction of an institutional guideline: extent of application and implementation of its recommendations. J Vasc Nurs. 2015;33:72–78.
9. Pannucci CJ, Bailey SH, Dreszer G, et alValidation of the Caprini risk assessment model in plastic and reconstructive surgery patients. J Am Coll Surg. 2011;212:105–112.
10. Khorgami Z, Mofid R, Soroush A, et alFactors associated with inappropriate chemical prophylaxis of thromboembolism in surgical patients. Clin Appl Thromb Hemost. 2014;20:493–497.
11. Swanson ECaprini scores, risk stratification, and rivaroxaban in plastic surgery: time to reconsider our strategy. Plast Reconstr Surg Glob Open. 2016;4:e733.
Copyright © 2017 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Society of Plastic Surgeons. All rights reserved.