Use of signals and systems engineering to improve the safety of warfarin initiation.

Warfarin-dosing algorithms combine clinical factors and dosing history with the current international normalized ratio (INR) to estimate the therapeutic warfarin dose. Unfortunately, these approaches can result in an overdose if the INR is spuriously low. Our goal was to develop an alert mechanism based on prior INRs in addition to the current INR. Using data from the Genetics InFormatics Trial (GIFT) of Warfarin to Prevent DVT, we analyzed warfarin dose estimates for days 3 through 11 that were ≥10 % higher than an average of the previous two dose estimates. We fit a stepwise mixed model to current and prior dose estimates, and subsequently compared the root-mean-square-error (RMSE) in predicting the final therapeutic dose using the GIFT algorithm versus the mixed model. From 861 dosing records (obtain from 556 patients), 646 dosing records (75 %) were randomly selected for the derivation cohort and 215 dosing records (25 %) for the validation cohort. Using one prior dose estimate improved the accuracy of the warfarin dose estimate. Compared to a dose estimate based on current INR (GIFT algorithm), the mixed model reduced the RMSE in the derivation cohort by 0.0015 mg/day (RMSE 0.2079 vs. 0.2094; p = 0.039). In the validation cohort, the RMSE reduction was not significant. A mixed model of dose estimates based on the current and most recent INRs shows potential to improve the safety of warfarin dosing. Clinicians should be cautious about aggressively escalating the warfarin dose after an INR that is lower than expected.

Genetics informatics trial (GIFT) of warfarin to prevent deep vein thrombosis (DVT): rationale and study design.

The risk of venous thromboembolism (VTE) is higher after the total hip or knee replacement surgery than after almost any other surgical procedure; warfarin sodium is commonly prescribed to reduce this peri-operative risk. Warfarin has a narrow therapeutic window with high inter-individual dose variability and can cause hemorrhage. The genetics-informatics trial (GIFT) of warfarin to prevent deep vein thrombosis (DVT) is a 2 × 2 factorial-design, randomized controlled trial designed to compare the safety and effectiveness of warfarin-dosing strategies. GIFT will answer two questions: (1) does pharmacogenetic (PGx) dosing reduce the rate of adverse events in orthopedic patients; and (2) is a lower target international normalized ratio (INR) non-inferior to a higher target INR in orthopedic participants? The composite primary endpoint of the trial is symptomatic and asymptomatic VTE (identified on screening ultrasonography), major hemorrhage, INR ≥ 4, and death.

Integration of genetic, clinical, and INR data to refine warfarin dosing.

Well-characterized genes that affect warfarin metabolism (cytochrome P450 (CYP) 2C9) and sensitivity (vitamin K epoxide reductase complex 1 (VKORC1)) explain one-third of the variability in therapeutic dose before the international normalized ratio (INR) is measured. To determine genotypic relevance after INR becomes available, we derived clinical and pharmacogenetic refinement algorithms on the basis of INR values (on day 4 or 5 of therapy), clinical factors, and genotype. After adjusting for INR, CYP2C9 and VKORC1 genotypes remained significant predictors (P < 0.001) of warfarin dose. The clinical algorithm had an R(2) of 48% (median absolute error (MAE): 7.0 mg/week) and the pharmacogenetic algorithm had an R(2) of 63% (MAE: 5.5 mg/week) in the derivation set (N = 969). In independent validation sets, the R(2) was 26-43% with the clinical algorithm and 42-58% when genotype was added (P = 0.002). After several days of therapy, a pharmacogenetic algorithm estimates the therapeutic warfarin dose more accurately than one using clinical factors and INR response alone.

Employee drug use, demographic characteristics, work reactions, and absenteeism.

Employees in a large work organization participated in an investigation of relationships between drug use and absenteeism and tardiness. Specifically, the study investigated the extent to which both self-reported and urine-screened drug use accounted for variance in several types of absenteeism, as well as tardiness, above and beyond that accounted for by demographic and work reaction variables. The results showed that employee drug use accounted for additional statistically significant variance in overall absenteeism and in absenteeism due to injuries and suspensions, as well as days tardy. Implications of these findings for organizational drug testing are discussed.

Social and psychologic influences on employment of married nurses.

Seven summary factors were obtained from a principal components factor analysis and Varimax rotation of 21 variables, based on 145 pieces of information given by 1,998 nurses in metropolitan Detroit, Michigan, in 1973. Study nurses were under 60 years of age, were married and living with spouse, and had at least one child 18 or younger. The factors were: career desirability, professional attitude, professional behavior, achievement personality, conducive home situation, economic value of work, and satisfaction with nursing. When these factors were compared with employment status-1) current employment activity of all subjects, 2) subjects whose employment status was constant for five years, highest scores were registered in both categories on career desirability, professional behavior, and economic value of work. Both groups of nurses scored lowest on satisfaction with nursing, with the five-year employees scoring lower. When the seven factors were correlated with employment status while controlling financial need and age of youngest child at home, highest correlation scores resulted for professional behavior, career desirability, and, in the case of those with financial need, on the economic value of nursing.