In Reply

Article Outline

• Copyright

The authors wish to thank Dr White and his colleagues for pointing out a potential flaw in our study design. Based on their suggestion and concerns, we reran the analysis without the V12.51 code. As shown in Table 1, the results of our analysis did not change. Even when the V code was excluded from the analysis, there was no difference in the odds of any venous thromboembolic (VTE) event among total knee arthroplasty (TKA) patients who received aspirin, warfarin, or injectable drugs (low–molecular-weight heparin or synthetic pentasaccharides) for VTE chemoprophylaxis.

Table 1. Adjusted Odds of Having Any VTE Event According to VTE Chemoprophylactic Agent in TKA Patients

	Model 1 (ICD-9 Secondary Diagnosis Code V12.51 Excluded From the Analysis) Adjusted OR (95% CI)	Original Model Adjusted OR (95% CI)
VTEP agent
Aspirin	Ref	Ref
Injectable (LMWH or synthetic pentasaccharide)	0.98 (0.59, 1.62)	1.03 (0.76, 1.39)
Warfarin	1.17 (0.73, 1.87)	1.36* (1.02, 1.82)

ICD-9 indicates International Classification of Diseases, Ninth Revision; OR, odds ratio; CI, confidence interval; LMWH, low–molecular-weight heparin.

We would like to reemphasize, as we did in our article, that our results do not suggest that aspirin is more efficacious than warfarin or low–molecular-weight heparin as a VTE prophylactic agent in TKA patients. However, our results do suggest that aspirin, when used in conjunction with other modern clinical care protocols, may be an effective VTE chemoprophylactic agent in certain TKA patients. Given the observational, retrospective design of our study, our conclusions should be considered hypothesis generating, rather than conclusive evidence of the comparative safety and efficacy of aspirin for use in VTE prophylactic regimens after TKA. However, our results, along with results from other observational studies, provide justification for future trials of multimodal VTE prophylactic strategies involving aspirin and other chemoprophylactic agents in TKA patients, and evaluation of the relative risks and benefits of these strategies.