Predictive value of the present-on-admission indicator for hospital-acquired venous thromboembolism

Background: Hospital-acquired venous thromboembolic (HAVTE) events are an important, preventable cause of morbidity and death, but accurately identifying HA-VTE events requires laborintensive chart review. Administrative diagnosis codes and their associated "present-on-admission" (POA) indicator might allow automated identification of HA-VTE events, but only if VTE codes are accurately flagged "not present-on-admission" (POA = N). New codes were introduced in 2009 to improve accuracy. Methods: We identified all medical patients with at least 1 VTE "other" discharge diagnosis code from 5 academic medical centers over a 24-month period. We then sampled, within each center, patients with VTE codes flagged POA =N or POA=U (insufficient documentation) and POA =Y or POA =W (timing clinically uncertain) and abstracted each chart to clarify VTE timing. All events that were not clearly POA were classified as HA-VTE. We then calculated predictive values of the POA = N/U flags for HA-VTE and the POA = Y/W flags for non-HA-VTE. Results: Among 2070 cases with at least 1 "other" VTE code, we found 339 codes flagged POA = N/U and 1941 flagged POA = Y/W. Among 275 POA= N/U abstracted codes, 75.6% (95% CI, 70.1%- 80.6%) were HA-VTE; among 291 POA = Y/W abstracted events, 73.5% (95% CI, 68.0%-78.5%) were non-HA-VTE. Extrapolating from this sample, we estimated that 59% of actual HA-VTE codes were incorrectly flagged POA = Y/W. POA indicator predictive values did not improve after new codes were introduced in 2009. Conclusions: The predictive value of VTE events flagged POA =N/ U for HA-VTE was 75%. However, sole reliance on this flag may substantially underestimate the incidence of HA-VTE.