The incidence of

diagnosed VTE during residence in the current study was higher than reported in 3 earlier nursing home studies16, 17 and 18 but equivalent to that of a second of 2 databases in one of these studies.16 Compared with the current study finding of 3.68 cases per 100 PY, VTE incidence rates in nursing home studies were 1.2 to 1.5 (MCMRP data/Minnesota),16 3.6 (Rochester Epidemiology Project data/Minnesota),16 1.3 (MDS and Medicare data/Kansas),17 and 1.4 to 1.6 (medical chart data/Israel)18 per 100 PY. The high incidence rate found in our study may be a consequence of differences in the pool of nursing homes studied BGB324 molecular weight (eg, a potentially greater number of residents receiving subacute care) or in the methods used, or it may be due to the later time period (2007–2009) than the earlier studies (1988–2001). The effect of changes in resident case-mix or a historic trend in the incidence of VTE remain unknown given the

lack of details in the current and earlier studies regarding levels of resident acuity and changes in criteria to diagnose VTE. Findings buy Screening Library from the Rochester Epidemiology Project16 would suggest that the MDS might be undercounting the incidence of fatal VTE, especially because residents who die in the hospital after nursing home discharge are less likely to have VTE recorded in the final MDS assessment. PE events may be especially undercounted. In a recent national study25 of hospitalizations with a diagnosis of VTE, the ratio of DVT to PE was much lower than our findings: crude estimated average annual rates in that study were 0.152 (DVT) and 0.121 (PE) per 100 hospitalizations, respectively; the relative proportion due to PE declined with advancing age, although in an earlier community study,6 the inverse

relationship was observed. The high incidence rate observed in our study TCL might also be a consequence of the growth in associated risk factors among hospitalized patients admitted to nursing homes in recent years with high disease acuity, short hospital stays, and increased use of surgical and other interventional procedures. Improved diagnostics for recognizing asymptomatic VTE may be a key factor, although we have no means of describing how newer diagnostics, such as portable Doppler ultrasound, have affected incidence rates over time. Stein et al26 found that the incidence of DVT in hospitalized patients increased from 0.8% to 1.3% of all hospital admissions over the period 1979 to 1999, yet the incidence of PE remained unchanged at 0.4%. These authors hypothesized that increased use of venous ultrasound may have increased DVT incidence, and early diagnosis and treatment of DVT may have prevented a concurrent rise in PE.26 Our study found a 1:5 ratio of PE cases to DVT cases during residence.