using the STA-Compact instrument (Diagnostica Stago, Parsippany, NJ) was used to quantify anti-Factor Xa (LMWH) activity for enoxaparin. The sensitivity of this assay is 0.2 U/mL and within run imprecision is 5.5 (% CV) at 1 U/mL. The assay is linear between 0.2 and 2.0 U/mL. All anti-Factor Xa levels were analyzed by technicians blinded to the assigned treatment regimen. The target range for peak anti-Factor Xa levels was chosen to be 0.2-0.5 IU/mL [14].Statistical analyses.. The sample size for this pilot study was chosen to provide a cohort large enough to identify differences between groups, based on previous studies [17]. Descriptive statistics were used to calculate summary data. Data are represented as the mean ± SD, unless otherwise indicated. For all analyses, continuous variables were assessed for normality visually and with skewness and kurtosis tests (version 11.0, StataCorp, College Station, TX 77845). Parametric, two-tailed t-tests or ANOVA were used for continuous variables and the chi-square and Fisher's exact test for categorical variables with a predetermined alpha level of P < 0.05. Stepwise, multiple regression analyses were used to identify any pre-specified variables potentially affecting peak anti-Factor Xa levels, including age, actual body weight, BMI, time (enoxaparin dose administration to anti-Factor Xa measurements), gender, or estimated creatinine clearance.
AcknowledgmentsAuthors thank all the patients that agreed to participate in this study, Ms. Pam Proctor and Linda Kelly for their research oversight, Dr. Chris Lehman for his assistance with anti-Factor Xa measurements, and Diana Lim for her assistance with illustrations and tables.